Report on the 1990
AASHTO . FHWA - NAPA - SHRP - TAI - TRB APPROXIMATE CONVERSIONS TO SI UNITS APPROXIMATE CONVERSIONS FROM SI UNITS 111 symbol When You Know Multiply By To Find Symbol Symbol When You Know Multiply By To Find LENGTH LENGTH
in inches 25.4 millimetres mm milliietres 0.039 inches in feet 0.305 metres m m metres 3.28 feet ft ; yards 0.914 metres m metres 1 .OQ yards yd mi miles 1.61 kilometres km k”, kilometres 0.621 miles mi
AREA AREA
ir+ square inches 645.2. millimetres squared mm2 millimetres squared 0.0016 square inches in2 square feet 0.093 metres squared mz m2 me&es squared 10.764 square feet w s square yards 0.636 metres squared d ha hectares 2.47 acres ac ac acres 0.405 hectares ha kn? kilometres squared 0.386 square miles mi2 mi2 square miles 2.59 kilometres squared kn?
. VOLUME VOLUME mL milliliires 0.034 fluid ounces fl 02 fluid ounces 29.57 milliliies mL floz L liies 0.264 galkxts gal gal gallons 3.765 liires L m3 metres cubed 35.315 cubic feet P It’ cubic feet 0.026 metres cubed m3 m3 metres cubed 1.308 cubic yards W yd3 cubic yards 0.765 metres cubed ma NOTE: Volumes greater than 1000 L shall be shown in m3. MASS
9 grams 0.035 ounces 02 kilograms 2.205 pounds MASS x megagrams 1.102 short tons (2000 lb) F 02 ounces 26.35 grams 9 lb pounds 0.454 kilograms kg T short tons (2000 lb) 0.907 megagrams MS TEMPERATURE (exact)
“C Cekius 1X+32 Fahrenheit “F TEMPERATURE (exact) temperature temperature OF 32 96.6 “F Fahrenheit 5( F-32)/9 ;:2 Cekius “C -40 0 40 60 120 160 200 temperature temperature r’;‘,“,‘~~:~,‘~,~l,,:‘;‘,‘,“,’ -20 0 20 60 60 ‘g -G 37?
l SI is the symbol for the International System of Measurement (Revised April 1989) III EUROPEAN ASPHALT STUDY TOUR
1990 SPONSORING ORGANIZATIONS
American Association of State Highway and Transportation Offtcials
Federal Highway Administration
National Asphalt Pavement Association
Strategic Highway Research Program
The Asphalt Institute
Transportation Research Board
ACKNOWLEDGEMENT
The sponsors and members of the European Asphalt Study Tour team would like to express our appreciation and thanks to all the people in the countries visited who contributed to making the trip the success that it was. We would also like to extend a special debt of gratitude to two individuals from the Federal Highway Administration--Mr. Richard F. Weingroff and Mrs. Deborah L. Stroessner--for their efforts in editing and rewriting sections of the report prepared by members of the tour group, and for the proofreading, graphic design, and page layout work performed.
This report is published by : American Association of State Highway and Transportation Officials, 444 North Capitol Street, NW., Suite 225, Washington, D.C. 20001
Permission to reproduce material contained within the report is hearby granted, June 1991.
ii TABLE OF CONTENTS
I. INTRODUCTION by Federal Highway Administrator Thomas D. Larson l-6
II. TOUR PARTICIPANTS ...... 7-10
III. AN OVERVIEW ...... 11-26
0 Table 1 - Demographics ...... 14 0 Table 2 - Highway Factors ...... 14 0 Table 3 - Taxation Effort ...... 15 0 Stronger Emphasis on Durability ...... 16 0 Structural, Not Visual, Factors Trigger Rehabilitation ...... 17 0 Stronger Emphasis on Noise Reduction and Skid Resistance ....17 0 Asphalt Modification ...... 18 0 Innovative Special-Purpose Mix Designs and Advanced Mix-Design Systems ...... 19 0 Scale, Diversity, and Efficiency ...... 20 0 Performance-Enhancing Contracting Procedures ...... 21 0 Environmental Concerns ...... 21 0 Stronger Research Emphasis ...... 22 0 Pending Market Changes ...... 22 0 Industry/Government Relationships and Industrial Structure ....23 Public/Private Cooperation ...... 23 Concentrated Industry Structure ...... 24 0 Summary ...... 24
IV. TRIP SUMMARIES ...... 27-64
o Sweden ...... 29 o Denmark ...... 35 o Germany ...... 39 0 Italy ...... 45 o France ...... 51 o United Kingdom ...... 57
se. 111 V. INNOVATIVE ASPHALT TECHNOLOGY . . . . ; ...... 65-98
o Possible Uses of European Technology in the United States .....67 o Stone Mastic Asphalt ...... 69 General Description ...... 69 Stone Mastic Asphalt in Germany ...... 72 Stone Mastic Asphalt in Sweden ...... 75 Stone Mastic Asphalt in Denmark ...... 81 o Porous Asphalt ...... 82 General Description ...... 82 Porous Asphalt in Sweden ...... 83 Porous Asphalt in Germany ...... 86 Porous Asphalt in France ...... 87 o Modified Asphalts and Asphalt Aggregate Mixtures ...... 90 General Remarks ...... 90 Stone Mastic Asphalt and Porous Asphalt ...... 90 Very Thin Asphalt Concrete (France) ...... 90 Paver-Laid Chip Seal (France) ...... 91 Gussasphalt (Germany) ...... 92 Hot-Rolled Asphalt and Bitumen Macadam (United Kingdom) ...... 94 o Other Special Purpose Mixtures ...... 96 o Mixture Design Techniques and Test Apparatus ...... 97 Novel Mixture Design Techniques ...... 97 Novel Test Apparatus ...... 100 References ...... 103 VI. APPLICATION of FINDINGS ...... 105-112
o Asphalt Pavement Mixtures ...... 107 o Laboratory Equipment ...... 109 0 Innovative Contracting Practices ...... 110 o Research ...... 110
VII. ACRONYMS, DEFINITIONS and TECHNICAL TERMS . . . . . 113-116
APPENDIX: Technical Project Data ...... 117-184
A metric conversion table has been provided on the inside front cover for your convenience. A list of commonly used acronyms and technical terms has also been provided to assist you. It can be found on page 115.
iv INTRODUCTION 3
INTRODUCTION by Thomas D. Larson Federal Highway Administrator
For the average motorist, one question about highways is of top priority: is the pavement smooth? Dating back to the 1970's the answer to that question has, unfortunately, often been “no.”
The reasons for the problem are many. Some involve political decisions, such as how much funding is available for pavement maintenance. But to a large extent, the issues are tech- nical. How can we make our predictions about pavement use more reliable? What is the best design? What surface is most durable for current traffic loadings? How can we best recycle old pavements? Just to cite a few.
In addition to the usual research and knowledge gained from experience, we have launched several major efforts to find the answers. The best known and the most promising is the Strategic Highway Research Program (SHRP). The need for new or improved pavement technologies was one of the driving forces behind the SHRP’s development and most of its work is directed toward these technologies. The result of the SHRP’s efforts should be recommendations for both the industry and the State highway agencies for improving the durability and longevity of the Nation’s pavements.
One element of pavement research has, however, been missing--until now. That element is research into how other countries build and maintain their pavements. This is not an idle question. During my years of teaching at Penn State, I had the opportunity to work with engineers from the United Kingdom and Sweden, and I learned many new and innovative techniques to deal with common highway problems. I also learned that we can gain a great deal through joint efforts with our counterparts in other countries who have advanced the state-of-the-art in roads and bridges.
Since being appointed Federal Highway Administrator, I have gained increased respect for the European highway community’s knowledge and understanding of pavements. This renewed respect is a result of my own observations of European highways in the past 2 years, as well as conversations with European experts who have visited the United States to learn how we solve common problems. Although the purpose of their visit in many cases is to gain knowledge about SHRP and the Federal-aid highway program, they often comment on the poor condition of pavements in the United States and contrast them with their own experience in Europe.
European Asphalt Study Tour 1990 4
The National Asphalt Pavement Association (NAPA) provided the impetus for the 1990 European Asphalt Study Tour (EAST). John Gray, President of the NAPA, asked me to promote a closer relationship between government and industry asphalt experts and to expand the concept to include European experts. He proposed an “on-the-ground” pilot program to review and evaluate foreign pavements and asphalt technology.
I agreed, as did the American Association of State Highway and Transportation Officials (AASHTO), and we decided to arrange a study tour of Europe. The objective was to exchange ideas and experience with highway agencies and the construction industry in Europe on design, production, and placement of asphalt pavements. We were particularly interested in the design of asphalt wearing courses, the use of asphalt modifiers and the benefits they offer to improve the durability of asphalt pavements, as well as recycling--both hot and cold. In addition, we were interested in contracting practices that would be inno- vative in the United States and cooperative public/private activities, not only in design and financing, but in research into new materials,‘methods, and machines. Most important, we wanted not only to discuss these and other subjects, but to see European technology at work.
Working together, the AASHTO, the NAPA, and the Federal Highway Administration (FHWA) selected a 21-member study group that included six AASHTO and eight industry representatives, as well as the Chairman of the Transportation Research Board, the President of The Asphalt Institute, and two SHRP officials. I asked Deputy Federal Highway Administrator Gene McCormick to represent the FHWA.
Through cooperation with six government and industry representatives in Europe, we arranged a 14-day study tour of six countries: Denmark, France, Germany, Italy, Sweden, and the United Kingdom. It began on September 7, 1990, with a flight from Dulles Airport to Goteborg, Sweden, and ended on September 22 with weary study tour participants arriving at Dulles after a flight from London. Whatever else the tour may have been, it was an exhausting experience for all concerned.
If the participants began with any chauvinistic ideas about the superiority of United States technology, they quickly realized we have a lot to learn from Europe about asphalt pavements and about pavement philosophy in general. European pavements ;are, better than ours and it’s no accident. The Europeans invest more in research, development, and deployment of new pavement technology. They build their pavement foundations better. They use innovative--for us--surfaces, such as Stone Mastic Asphalt (SMA), and mix in additives to a greater extent and with better results than we do. Government and industry have a closer relationship--probably closer than would ever be possible in the United States--that encourages innovation and quality. And, the Europeans maintain their pavements to get the maximum life out of them.
European Asphalt Study Tour 1990 5
Upon return to the United States, the participants developed the plan for this report. It describes the mission of the tour, and provides an overview, as well as a description of the activities observed in each country; summarizes the findings not only for asphalt technology but for innovative contracting practices and innovative construction equipment; and provides a plan for applying these findings in the United States.
The implementation plan may be the most important part of the report, because we do not see the 1990 EAST as the culmination of our efforts. It’s just the start. The FHWA will work with the NAPA, the AASHTO, the SHRP, and other industry and State officials to begin incorporating what we have learned into everyday practice.
The success of the study tour is the result of a lot of hard working people. Dick Morgan of the NAPA, Frank Francois of the AASHTO, and Doug Bernard of the FHWA deserve special thanks for making the arrangements. At times, the tour--trying to get 21 people across Europe in 14 days--was something like doing a jigsaw puzzle, but amazingly, they fit all the pieces together and the picture proved to be perfect.
In the end, though, the success of the study tour depended on the willingness of European highway and industry officials to share their ideas and their technology. Tour participants found their European counterparts not only willing but eager to do so. This was especially appreciated because the tight schedule imposed restrictions on the European hosts, too. Nevertheless, the schedules were adhered to in every case, and with good cheer. In every country, team members made many new friends.
For too long, we have seen international technology transfer as a one-way street, with the United States showing other countries how to build better highways. Today, we can no longer afford such an attitude. Our transportation network is our greatest economic asset. If we do not give it our best--and Europe’s best--we will undermine our own success. Internationally, our ability to compete in the world markets is dependent on our ability to demonstrate our expertise. We are, today, a world leader in highway technology, but that reputation will slip, along with our competitiveness, if we do not expand our technology sharing, in both directions, with the international community.
Some of the European technologies seen, such as SMA and some mix design testing equipment, will be displayed at AASHTO’s ‘Technology Transfer Fair,“ in conjunction with that organization’s annual meeting in Milwaukee, Wisconsin. The “Fair” is scheduled for October 12 and 13, 1991, and booths will be staffed by specialists, who can discuss the technologies displayed and answer questions.
European Asphalt Study Tour 1990 TOUR PARTICIPANTS 9
TOUR PARTICIPANTS
American Association of State Highway and Transportation Offkials
Mr. Thomas H. Espy, Jr., Chief Engineer, Alabama Highway Department Mr. Byron C. Blaschke, State Engineer-Director,Texas State Department of Highways and Public Transportation Mr. James D. Quin, Chief Engineer, Mississippi State Highway Department Mr. Bernard B. Hurst, Director, Ohio Department of Transportation Mr. Francis B. Francois, Executive Director, AASHTO Mr. Dwight Bower, Deputy Director, Colorado Department of Highways Federal Highway Administration
Mr. Gene McCormick, Deputy Administrator Mr. Edwin Wood, Regional Administrator Mr. Douglas A. Bernard, Chief, Demonstration Projects Division Mr. Robert A. Ford, Chief, International Cooperation Division National Asphalt Pavement Association
Mr. Lloyd 0. Thompson, President, Border States Paving, Inc. Mr. Ned W. Bechthold, President, Payne & Dolan, Inc. Mr. G. W. “Bill” Jones, President/Chief Executive Officer, APAC, Inc. Mr. Roger L. Yarbrough, President, University Asphalt Company Mr. Robert M. Thompson, President, Thompson-McCully Company Mr. Fred M. Fehsenfeld, Chairman of the Board, Contractors United, Inc. Mr. Richard D. Morgan, Vice President, National Asphalt Pavement Assoc. Strategic Highway Research Program
Mr. Damien J. Kulash, Director Mr. Edward T. Harrigan, Asphalt Program Manager The Asphalt Institute
Mr. Gerald S. Triplett, President, The Asphalt Institute Transportation Research Board
Mr. Wayne Muri, Transportation Research Board Chairman, and Chief Engineer, Missouri Highway and Transportation Department
European Asphalt Study Tour 1990 OVERVIEW 13
THEl990EUROPEANASPHALTSTUDYTOUR
ANOVERVIEW In mid-September 1990, a team of pave- highways, as it is many other aspects of ment specialists from the United States life in Europe. For example, a highway participated in a 2-week tour of six system is emerging that is comparable in European nations. The team included many ways to the Interstate System in the representatives from the AASHTO, the United States. The European motorway FHWA, the NAPA, the SHRP, TAI, network totals some 40,000 km (about and the TRB. The full European Asphalt 25,000 miles), including approximately Study Tour (EAST) team visited, in 13,500 km (8,400 miles) of toll roads. It order, Sweden, Denmark, Germany, will be capable of moving goods by truck France, and the United Kingdom, while from Norway in the north to Italy in the a subcommittee drawn from the South, and from Eastern Europe to the AASHTO and the FHWA participants Atlantic ports. visited Italy. Despite these similarities, the six nations The six nations have much in common differ from the United States and from with the United States. All are indus- each other in many ways. The tables trialized, have extensive highway and found on the following two pages illus- road systems, and rely increasingly on trate some of the differences in demo- motor vehicles for moving people and graphics, including density of population freight. While the six nations have (table 1); the number of vehicles per mature railroad networks that move large person and on an area basis as well as the numbers of passengers and considerable density of the road system (table 2); and freight, the number of motor vehicles and the overall approach to government fin- the use of trucks to move goods have ance (table 3). In addition, while all the grown constantly. All the nations visited nations visited are Western industrial have modern, capable highway agencies democracies, each country has a more and a mature construction industry. centralized government than does the Some also have extensive highway United States . The Federal-State part- research facilities. nership that has been essential to the success of the Federal-aid highway pro- The emerging European Economic gram in the United States has no Community of the 1990’s will cause tar- counterpart in Europe. iff and trade barriers to decline among the nations, leading to a confederation The 1990 EAST visited asphalt mixing that--to some extent--will resemble the plants, contracting firms, government United States, but without our strong agencies, laboratories, and material national government. The coming suppliers, and inspected scores of pave- together of the nations is affecting ments and ongoing paving projects in
European Asphalt Study Tour 1990 14
Table 1 d
NATIONAL STATISTICAL COMPARISONS DEMOGRAPHICS
Nation W Population Pop. Density Percent Urban Auto Expense (millions) @erson/sq km) (percent) as % of (1990) (1986) (1985) Pers. Spndg. (1980-85)
U.S. 248.0 25.7 74 6 Sweden 8.2 18.6 86 2 Denmark 5.2 118.8 86 W. Germany 60.7 245.6 86 Italy 57.4 190.0 67 France 55.4 101.3 73 U.K. 55.8 231.9 92
Table 2 aJ
NATIONAL STATISTICAL COMPARISONS HIGHWAY FACTORS
Nation ti Vehicles Pers. Per Veh. Veh. Density Hwy. Density (millions) (tot./per car) (veh./sq km) wss km) (1987) (1987) (1987)
U.S. 179.04 1.411.8 14.5 0.67 Sweden 3.63 2.312.5 7.6 0.4 Denmark 1.88 2.713.2 nla n/a W. Germany 30.11 2.012.1 113.9 1.98 Italy 24.72 2.312.5 77.5 1.01 France 24.85 2.212.5 40.0 1.46 U.K. 23.02 2.512.8 74.1 1.53
European Asphalt Study Tour 1990 15
Table 3 d
NATIONAL STATISTICAL COMPARISONS TAXATION EFFORT
Nation W Tot. Tax Receipts Road Taxes as % of % of User Fees as % of GNP Total Receipts Used for Roads (1985)
U.S. 29.2 4.7 100 Sweden 50.5 6.3 34 Denmark 49.2 6.2 31 W. Germany 37.8 3.7 64 Italy 34.7 n/a da France 45.6 15.0 n/a U.K. 38.1 11.5 23 &Tables 1,2, and 3 are drawn from a variety of sources, including the World Bank, the International Road Federation, The World Almaw, the Organization for Economic .. Cooperation and Development, and MVMA Motor Vehr& Facts and Frmrres , 89. Statistics compiled prior to the unification of Germany. b/The nations are listed in the order visitied, with the United States added as the first country, for comparison purposes. five of the countries visited--Sweden, The highway systems observed during Denmark, Germany, France, and the the study tour are similar to their United Kingdom. The subcommittee United States counterparts in some that visited Italy inspected a mixing plant, ways, but different in others. Among a paving project, as well as roadway fac- the similarities: ilities, and met with officials of govern- ment agencies and Societa Autostrade, a o All six countries have Interstate-type concessionaire with responsibility for a motorways. Like their United States large portion of Italy’s toll motorways. counterparts, the motorways typically While some local roads were observed make up a small percentage of the first hand, the tour concentrated pri- nation’s overall road network but carry marily on major highways and motor- large shares of its highway traffic ways comparable to the Interstate System . (approximately 25 percent). and similar high-volume highways in the United States.
European Asphalt Study Tour 1990 16
Heavy motor truck traffic is concentra- This observation is ‘true even though ted on these routes, often representing motor truck usage in Europe is around 20 percent or more of all vehicles. 20 percent of the total traffic, with vol- umes growing on many highways, and Road professionals in every country European axle weights substantially ex- complained of inadequate road-invest- ceed those allowed in the United States. ment levels. Germany, for example, allows an 11.5 metric ton axle loading, or about 25,400 pounds, while France allows a 13 metric The observations reported here are im- ton axle loading, or about 31,200 pounds. pressions based on the study tour’s site These weights may also be carried in Eu- visits, dozens of interviews, and many rope on “super singles”--a tire confignra- hundreds of miles of highway travel by tion that concentrates much of the weight motor coach. The impressions, however, of the vehicle in a fairly narrow path. are just that: subjective comments based on the people met and the things seen. Aside from superior pavement condi- tions, the European highways are gener- A few impressions will help put the ally not more advanced than comparable technologies, procurement procedures, United States highways. For example, and organizational roles into context. By many routes were congested and oppos- far the study team’s most striking obser- ing lanes of traffic generally ran close vation was that the pavements on Euro- together. The alignment of lesser routes, pean motorways and trunk routes are in particularly in the United Kingdom, was superior condition. The extreme forms not always suited to modern traffic needs. of distress that are evident in many parts of the United States--rutting, raveling, cracking, and potholes--were, simply, The superior pavement condition of rarely seen. Even pavements that were European motorways appears to stem being rehabilitated or resurfaced were in from, or be related to, several differences fairly good condition by United States between United States and European standards. approaches:
STRONGER EMPHASIS ON DURABILITY Most of the countries visited use a strategies. In the United Kingdom, a 40-year analysis period for the design of 40-year life-cycle cost analysis is required their motorway pavements, as opposed to for all pavement designs. the 20-year design period used in the United States. In the 40-year analysis, Most of the countries emphasize building European highway officials consider the a sound subgrade and base rather than initial pavement design and various reha- trying to solve subgrade problems in the bilitation strategies, as well as the antici- pavement design process. Structurally pated life and cost of the design and the sound design practices are generally used even when they impose significant con-
European Asphalt Study Tour 1990 17 struction costs through excavation and countries visited aim for longer design- replacement of subgrade material or in- life than in the United States and appear corporation of active drainage systems. more willing to increase initial costs to The most striking instance of this was in avoid problems later. Strong, well- Germany, where one official stated that, drained bases and subbases are the norm “We no longer design roads; we have throughout the countries visited, rather done that. Now, we simply look at a table than the exception. and select the appropriate pavement design.” Five of the six countries have prohibited the use of studded snow tires. The excep- German pavement design practices are tion is Sweden, where studded tires are a predicated on the fact that the subgrade major source of rutting. Relatively short is structurally sound and adequately lives for wearing courses in Sweden are drained. Over-design of pavement struc- inevitable because of the damage from tures is not needed as a way of compensat- studded tires. One unusual aspect of the ing for inadequacies in the subgrade. The resulting accelerated replacement of economic implications of high durability wearing courses is that the pavement were not challenged. On the contrary, structure is continually restored or even the German representative noted that, improved. When resurfacing takes place, “Whether or not it is more economical to the underlying structure is still sound and tolerate some frost heaves is a debate we relatively new. This structural predict- should not start.” ability has helped to make some innova- tive forms of contracting for surface The German approach to sound design courses work effectively (namely, func- stands out as exceptional, even among tional contracts and guarantees). European practices. However, all the
STRUCTURAL, NOT VISUAL, FACTORS TRIGGER REHABILITATION Pavement-management practices in the evident, it is too late to correct structural countries visited appear to be driven problems. Societa Autostrade in Italy, for more by structural condition, and less by example, virtually ignores visual distress visual condition, than is the case in the on its 3,000 km of motorways in favor of United States. Systems for monitoring twice-yearly total pavement surveys with pavement condition and for programming condition-measuring devices that exam- rehabilitation projects rely primarily on ine skid resistance, bearing capacity, deflectograph or falling-weight deflection rutting and surface texture, profile, and measurements. Some European officials other cross-slope geometrical noted that by the time visual distress is characteristics. STRONGER EMPHASIS ON NOISE REDUCTION AND SKID RESISTANCE Great emphasis is placed on skid are serious concerns in the United States resistance and pavement noise reduction as well, they play a much more prominent in all the countries visited. While these role in determining when and how
European Asphalt Study Tour 1990 18 resurfacing work is done in Europe. used is itself a subject of direct public Open-graded friction courses, under such participation--in at least some countries, names as drain asphalt and porous asphalt the noise properties of different riding (PA), are advocated in several countries surfaces are matters of public knowledge. largely because of favorable noise and An agency’s choice of treatment may be skid properties. Some of the concerns influenced by popular demand. raised about the durability of earlier ver- sions of these mixes appear to have been As in the United States, noise barriers are resolved by the use of modified binders. common, although their extent and the However, long-term performance infor- number of design variations are greater mation on durability is not fully available. along European motorways. This fact, coupled with the European public’s Because of concern about noise, the involvement in decisions on riding public in Europe appears to be involved surface, may be good indicators of where in riding surface design decisions to a far the United States is headed as traffic greater extent than is common in the increases and as our own public concerns United States. The type of riding surface about highway noise continue to grow. ASPHALT MODIFICATION European officials described many types Regardless of the extent, several nations of asphalt modification. They include clearly have drawn up high-performance mineral and cellulous fibers for SMA and standards or contracting approaches that the use of carbon black, EVA, SBS, poly- permit and, in fact, encourage contractors ethylene, and ground rubber in other mix to use a range of modified binders and designs, as well as the addition of secret innovative mix designs. Of the nations or proprietary materials whose nature is visited, France appears to make the larg- unclear (e.g., an ingredient identified to est and most sophisticated use of addi- the study tour only as “dope” was used in tives and modifiers, and French contrac- one contractor’s modified mixtures). tors have developed several patented pavement materials. In Italy, to cite The use of these modifiers appears to another example, Societa Autostrade is be widespread, judging from the number making extensive use of proprietary of references and the time devoted to modified mixes and processes. them by the European hosts. On the other hand, the fact that they knew in It should be noted that compared with the advance of the study group’s desire to see United States, the nations visited often and discuss “cutting-edge” technology have fewer stable sources of asphalt. In undoubtedly encouraged a strong focus Sweden and Denmark, for example, on modification, even though it may not Venezuela is essentially the only source be common practice. Some comments of asphalt. The European nations find from contractors and officials suggested that developing specifications based on that modified binders still represent a the known characteristics of this asphalt is small, special-purpose nitch in the overall easier than if they had multiple sources. pavement market.
European Asphalt Study Tour 1990 19
INNOVATIVE SPECIAL-PURPOSE MIX DESIGNS AND ADVANCED MIX-DESIGN SYSTEMS Mix designs similar to the conventional, dictate for rut-resistant surfaces. How- continuous-graded designs employed in ever, the different aggregate gradings and the United States are used for much of the modifiers and filled mastics generally the construction, rehabilitation, and appear to prevent rutting, flushing, and maintenance of European motorways and bleeding. None of these conditions were trunk roads. All the countries visited, observed on anything approaching the however, also use special-purpose mix scale they are found in the United States. designs, particularly in surface courses, to enhance the resistance of high-volume Mix design systems in Europe are sirni- pavements to rutting, skidding, and, to a larly varied, as illustrated by these exam- lesser degree, fatigue and thermal ples from three of the countries studied: cracking. o Germany: Mix designs in the usual Examples of such mix designs are SMA sense of the term are not done. Rather, in Sweden, Denmark and Germany; hot mix designs for the surface and base rolled asphalt (HRA) and penetration courses on motorway projects are sel- macadam in the United Kingdom; ected from a series of standard designs gussasphalt in Germany; and special thin that have been developed through and very thin asphalt overlays in France. experience for various classes of traffic To achieve superior performance, these volume. mix designs tend to feature gap-graded aggregate blends and modified or low- o France: The national laboratory, the penetration grade binders, sometimes Central Laboratory of Bridges and with the addition of fibers, as in the case ‘Roads (Laboratoire Central des Ponts of SMA. Several of these designs are et Chaussees--LCPC), developed the intended to control rutting and other mix design system that is used today. distress for as long as 10 to 12 years under This system incorporates both gyratory heavy volumes of truck traffic and, in and rolling-wheel compactors, with Sweden, SMA is used to combat the sophisticated wheel-tracking and direct deterioration stemming from the use of tension equipment used to determine the studded tires. rutting, stripping, and load-related fatigue characteristics of trial mixes. The use of “large-stone” mixes, with top aggregate sizes of 40 mm (1.5 inch or o United Kingdom: The Marshall design more), to resist rutting does not appear to method is used by some county author- be prevalent in Europe. Surface courses ities (which correspond to the state generally employ a top aggregate size of highway administrations in the United from 11 to 16 mm (about .5 to .75 inches). States), but others rely on standard Many European mix designs also appear “recipe” designs with a history of good far richer in binder content than conven- service. tional wisdom in the United States would
European Asphalt Study Tour 1990 20
SCALE, DIVERSITY, AND EFFICIENCY In most of the countries visited, a few design differences, scale economics, and large companies appear to receive other factors. Amidst so many economic (through bid or negotiation) a large maj- factors, each of which differs from its ority of contracting jobs on motorways United States counterpart, isolating the and major national routes. At the same extra cost attributable to some individual time, asphalt paving contractors clearly performance-enhancing feature is not have to supply quality materials meet- possible. ing the numerous, diverse specifications of agencies at different levels of govern- In short, where higher quality was evident ments. Asphalt plant owners frequently in Europe, study tour participants could noted the large number of different mix not gauge cost-effectiveness with any designs--generally over 100--program- accuracy. The large disparity in final med into their batch-plant control rooms. cost means that when United States offi- The inefficiency of an excessive number cials or pavement experts examine a high- of mixes was broadly recognized. In fact, performance European technology, they it is part of the reason that the German should carefully evaluate likely cost-effec- national government decided to adopt a tiveness, as well as quality, in possible manageable number of standard pave- domestic applications. Improvements in ment designs, and why the United King- quality do come at a price, but while the dom’s standard-setting groups are quality is evident, the value, in relation to concentrating on a small number of cost, remains to be determined. “preferred designs.” What was clear to study tour partici- Production rates in the asphalt plants pants was that the European nations visited were typically one-half to one- visited have looked at the cost-benefit third the productivity of their United equation for building high performance States counterparts. Likewise, unit costs pavements on well engineered subgrades of paving materials and constructed pave- and bases--and have found such pave- ments ran two or more times the corres- ments to be in their national interest. ponding costs in the United States. The commitment to quality is obvious, and the Europeans have been willing to Comparing cost or production rates in pay the cost. This commitment is some- Europe and the United States, however, thing that Federal and State highway requires caution. The EAST participants officials in the United States should recognized the difficulty of interpreting carefully consider if this country intends European economic conditions in the to offer a highway system competitive United States context, due to different with that of the European Economic materials prices, hauling distances, tax Community in the 1990’s. systems, labor conditions and rates,
European Asphalt Study Tour 1990 21
PERFORMANCE-ENHANCING CONTRACTING PROCEDURES One of the most striking features of the Together, they apparently provide a European paving practice is the ability of working arrangement for tapping the European countries to stimulate contrac- experience and ingenuity of the contrac- tor innovations and apply them within a tor while maintaining sufficient control competitive process. These innovations to ensure public funds are spent effec- include the use of modifiers and additives tively. Contractors appear to accept the within asphalt-binders, the use of high- guarantee or warranty requirement, at quality aggregates, and new mix designs. least in part because of the existence of While components of some innovative good quality pavement designs that, in European mix systems are of a proprie- many cases, they had a role in formula- tary nature, public agencies are able to ting. The study tour participants believe obtain them by competitive procedures that in the absence of high quality pave- that do not require particular proprietary ment designs trusted by the contractors, materials or processes. Each country has European contractors would oppose its own approach, but these procedures guarantees and warranties. generally had two features that differ from the current process of competitive The countries visited do not generally use bidding in the United States: performance-based specifications, which gauge the quality of the finished product. o Specifications were broader than most They also do not use end-product speci- of the method specifications used in the fications, which pin down key character- United States, allowing contractors istics of the final product. Rather, the greater latitude to select effective European procedures reviewed during materials and designs; and the study tour generally depend upon guarantees and latitude within method 0 Contracts require contractors to offer specifications to build a contracting envi- guarantees or warranties that extend ronment that encourages contractors to 1 to 5 years after the work is completed. use advance technologies to enhance per- formance. In addition, Sweden has exper- imented with projects using completely The first feature gives the contractor greater responsibility in selecting an functional (design/build/maintain) speci- effective approach. The second holds the fications, with some apparent success. contractor accountable for that choice.
ENVIRONMENTAL CONCERNS Public concern about the environmental Because of the generally dense popula- aspects of highway construction in gen- tion and the proximity of plants to proj- era1 and asphalt paving in particular were ects, the European countries appear to clearly evident wherever the study tour rely on permanent plants, with portable went in Europe. Concerns covered topics units that can be relocated being the ranging from location of asphalt plants to exception. The choice of location for how the roads are constructed. permanent plants is a sensitive local land-
European Asphalt Study Tour 1990 22 use issue. As a result, totally enclosed temperatures than normal asphalt con- plants were seen in Germany and the crete) were tolerated in Germany, as United Kingdom, and landscaping were noticeable emissions from in-place requirements appeared to be extensive in recycling. When members of the study some cases. Common practice is for an tour inspected an asphalt recycling ma- asphalt plant to serve several contractors. chine in Italy, they found thick deposits Some plants were independently owned, on the exhaust stack, apparently left by while others were owned by groups of plant emissions and particulates. contractors. The study tour also observed the safety Generally, study tour participants found environment for construction workers. that at the paving site, environmental Some innovative work zone traffic man- regulations for laying asphalt pavements agement concepts were observed, espe- did not appear to be any stricter than cially in Sweden. Overall, however, safety those in the United States. Indeed, in work zones is apparently not generally blue-smoke emissions from gussasphalt emphasized to the same extent as in the paving (which requires higher United States. STRONGER RESEARCH EMPHASIS Tour participants found that the emphasis countries, laboratories were larger (in placed on highway and asphalt research, staff and budget) than the FHWA’s by both contractors and central govern- Turner-Fair-bank Highway Research ments, is much stronger in Europe than Center, even though the population of in the United States. Denmark, France, the countries is only 4 to 25 percent that Germany, Sweden, and the United Ring- of the United States. dom have large centralized research fac- ilities and capabilities, including full-scale Research and development by private pavement testing devices and test tracks contractors is not only common, but much (France and the United Kingdom), greater than in the United States. This is wheel-tracking tests for rutting, acceler- reflected in the diverse array of speciali- ated wheel-wearing devices for evalu- zed paving mixtures and equipment that ating surface treatments (Sweden and contractors have developed so they can Germany), rolling compactors for prepar- compete in European markets outside ing large test specimens, and extensive their own country. laboratory capabilities. In four of these PENDING MARKET CHANGES The planned adoption of uniform agencies are already required to solicit standards throughout the European bids from the entire European Economic Economic Community after 1992 has Community, not just from the country stimulated public officials, contractors, where the project is located. To date, and research laboratories to examine cross-national awards do not appear their own approaches and to prepare for cornmon on paving work, although some broader competition. On large-scale jobs, contracts for bridge projects and other
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specialized work have been awarded to national laboratories recently formed the contractors from other countries. As Forum of European National Highway standards become more uniform, con- Research Laboratories, an international tractors and materials suppliers are association that is helping to reconcile expected to be able to compete in their activities in the face of those broader markets. Large contracting firms changes. Development of the SHRP’s already appear to be exploring the binder and mixture specifications, which prospect of international expansion. are likely to be released in 1992, is being watched with considerable European Officials of the centralized research interest because parts of the SHRP’s laboratories likewise recognize that battery of performance-oriented changes planned for the post-1992 era specifications and tests could find uses will affect the need for, and suitability of, within the new system of standards. some current activities. The European INDUSTRY/GOVERNMENT RELATIONSHIPS AND INDUSTRIAL STRUCTURE The study tour participants found that the The United Kingdom: On at least some business climate in the European paving projects, only qualified companies sel- industry differs significantly from that in ected by agency officials are allowed to the United States in two main respects: bid. In addition, various lane-rental public/private cooperation and concen- approaches are used at the national and trated industry structure. county (state) levels so the duration of lane closure is factored directly into the Public/Private Cooueration cost comparison. Government and industry in Europe cooperate to obtain high quality, even Sweden: Only a few large, well- though costs may be higher. Industry qualified companies appeared able to plays a much more active role in research, offer the necessary assurances under product development, and new product the performance-guarantee system used testing than in the United States. The there. national governments cooperate with industry by helping to develop or approve Germany: A combined system of cost standardized tests, by arranging field and quality-related factors is used to trials of new industry products, and by select the most acceptable contractor, setting specifications that ensure ade- namely the one with the best combina- quate performance but permit sufficient tion of quality and cost. latitude to embrace innovative industry products. Each of these contractual approaches had subtleties that varied from country to The method used to select contractors country and even from project to project, also affects quality. For example: but each system differs from United States practices in several ways:
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In Europe, much greater emphasis and links, the European contracting industry latitude are given, within competitive is even more concentrated than the contracting procedures, to encouraging limited number of firms would imply. and hence achieving quality products; The concentrated industrial structure Government and industry work coop- helps explain how some features of the eratively to develop improved products; close industry/government association can work. For example, larger “up front” And, government officials in Europe investments in research and develop- have a much stronger ability than their ment make more sense in this structure, counterparts in the United States to limit as does industry’s acceptance of the competition to well-qualified contractors, government’s strong role in qualifying and to consider their performance on and choosing high-quality contractors. projects in the past and the quality of that work in the final selection process. Moreover, government authorities have a large influence on the management Concentrated Industrv Structure of each company. Perhaps the most pronounced cases of this are the French In Europe, the paving industry is more and Italian tollway concessions, which concentrated within a small number of are operated much like a utility in the large firms than is the case in the United United States. They appear to generate States, even after the smaller scale of neither excess profits nor potential losses. European countries is taken into account. As in the United States, though, conces- Further, the contractors are often linked sionaires or toll agencies can generate through overlapping ownership of shares, greater-than-minimum costs for provid- ownership of common suppliers, or other ing and maintaining their motorways, financial ties. In Italy, the national which the governments in Europe are government may even own substantial apparently willing to pay for in recog- stock in the contractor. Because of these nition of the obviously high-quality highways they receive.
SUMMARY Based on 2 weeks of discussions with substantially above United States limits private contractors and many government and truck traffic that often accounts for officials, as well as detailed observation 20 percent of highway usage. of pavements, plants, and laboratories, EAST participants formed several o Greater durability is engineered into general impressions: pavement structures in Europe, with more emphasis on providing well- o European motorways are in much better drained, structurally sound subgrades. condition than equivalent roads in the United States, despite axle weight limits
European Asphalt Study Tour 1990 25 o Rehabilitation is typically triggered by search laboratories. European hot-mix structural measures, not by the appear- contractors also do more research than ance of visible distress. their United States counterparts. o Concerns about noise reduction and 0 Research results tend to be more aggres- skid resistance dominate the timing and sively marketed in Europe, particularly in selection of surface treatments to a far France where the LCPC sometimes greater extent than in the United States. markets directly, or licenses manufac- turers to market, its proprietary inven- o European countries appear to be mak- tions. ing more use of modified binders, com- monly proprietary, than is the case in 0 The coming of standards in 1992 that the United States. will apply to the entire European Economic Community is a dominant o Innovative mix designs are applied on general concern of contractors and the wearing courses of heavily travelled governments alike. routes. The designs often use gap-graded mixes and modified or low-penetration 0 One response to the need for the binders (between 40-60 percent). development of European Economic Community standards may be the adop o The scale and diversity of hot-mix prod- tion of European performance specifica ucts, together with numerous economic tions, which could be more easily adapted features of the European environment, by each European nation to its own high result in unit costs for hot-mix products way system procedures and practices. that appear to be substantially above their United States counterparts. 0 European governments and the private sector work more closely than is true in o European countries have developed the United States. At least part of the contracting approaches that encourage reason for the presence of higher qual- contractors to innovate and enhance ity highways in Europe can be traced to the quality and performance of their this cooperation. products. 0 The concentration of Europe’s highway o Environmental controls on European industry into a few companies, often paving projects appear to be no greater with overlapping ownership and some- than in the United States and are perhaps times with a degree of ownership by looser, while zoning controls of asphalt government, provides for an improved plants in at least some countries appear climate of cooperation, but at the cost much stricter. of the intense competitive environment that exists in the United States and o European governments are much more provides the countries with lower cost active than governmental agencies in the highways. United States in supporting highway re-
European Asphalt Study Tour 1990 TRIP SUMMARIES
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SWEDEN Items with the Highest Potential for Goteborg area, reported use was 50 per- Implementation in the United States: cent. Swedish authorities have concluded that designing conventional asphalt con- o Stone Mastic Asphalt crete mixes with good shear resistance as well as satisfactory durability and resist- ance to cracking is difficult, if not impos- o Drainage asphalt (also known as PA) sible. In Sweden, the answer is SMA. o Contract administration procedures, in- The three main characteristics of an SMA cluding warranties and functional con- mix are: tracts 1. The coarse particles must form a stone ITINERARY skeleton with firm contact between the particles. The Swedish tour consisted of a Sunday afternoon seminar with government and 2. The glue between and the coating of industry officials, as well as tours of the coarse particles should consist of a projects, both active and completed, and void-less mastic. an asphalt plant. 3. The mastic must be stabilized so it does SUMMARY not drain off the coarse particles during storage, hauling, and laying. The Sunday afternoon seminar featured presentations on several subjects: Mastic, as used in this context, means the asphalt cement, fine aggregate (less than 1. Heavy duty asphalt pavements (SMA 2 mm), and filler. and PA). Stone Mastic Asphalt is a gap-graded 2. Government and industry perspectives mix using high-quality crushed aggregate on the Swedish experience with SMA with a maximum size of 16 mm. Approxi- and PA. mately 80 percent of the aggregate is larger than 2 mm, with 65 to 70 percent 3. The Swedish experience in functional larger than 8 mm. By weight, the binder contracts and the use of guarantees. content ranges between 6.6 and 7 percent of the total mix. The main additives used Unlike the other countries visited, to stabilize the mastic seem to be either Sweden faces the problem of extensive cellulose or mineral fibers. The fibers use of studded tires, which cause rutting. look like rock wool and are reported to In the northern region, 90 to 95 percent be approximately 1.5 mm long. In short, of all vehicles use studded tires. In the
European Asphalt Study Tour 1990 32 the SMA mix basically consists of two The price difference between SMA and parts: a rather single-sized coarse the standard asphalt concrete mix was aggregate and the mastic. difficult to tie down. Comments indica- ted, however, that SMA is somewhere Porous asphalt, sometimes called drain- between 10 and 12 percent more expen- age asphalt, is also receiving considerable sive. The cost of PA is somewhere attention in Sweden. This mix, which between the two. Top quality aggregate is seems to be similar to our open-graded used in all the mixes, even if the material friction courses and some plant mix seals, must be imported at significant cost. In has excellent noise reduction and skid May 1990, 40 Nordic asphalt technolo- resistance properties. It has not, how- gists compared different asphalt mixes ever, shown sufficient durability in with standard hot mix asphalt (HMA). Sweden. In the view of Swedish author- The table on the facing page shows the ities, this mix can be improved by using results. fibers or modified asphalt binders. They also emphasized that the existing surface One Swedish expert offered the opinion must be sealed prior to laying PA. that SMA and PA will dominate the surface market in Europe for the fore- Field reviews of projects completed and seeable future. Nobody argued with his underway generally confirmed what was conclusion. presented in the seminar. City streets surfaced with SMA and subjected to Cooperation between the private and heavy truck traffic and abuse from stud- public sectors in Sweden seemed very ded tires seemed to hold up well. A heav- good. In general, Sweden operates under ily traveled PA city street had a rut depth a quality assurance process and requires of approximately 25 mm after 6 years. 2- to 3-year warranties on asphalt pave- The pores in the mix appeared to be ments. Neither government nor industry clogged with debris, and this blockage has any problems with the warranty con- tends to destroy the strong skid resistance cept. The required surety of up to 5 per- of the mix. cent of the contract price is released after satisfactory completion of the warranty. The two active projects reviewed involved SMA construction. The contractor for In the early 1980’s, Sweden tried two each project used different SMA mixes, projects with completely functional as was evident from their appearance. (design/build/maintain) specifications, Compaction was achieved with steel- including a maximum tolerated rut depth, wheeled rollers. As a general rule, smoothness, and friction. No defects pneumatic-tire rollers are not used on were allowed and warranties of 5 years surface courses in Europe. The typical were required. These projects were suc- SMA overlay in Sweden is between 30 cessful, but have not yet resulted in fur- and 40 mm thick. Both active projects ther functional contracts. Swedish offi- have thicknesses of approximately 30 mm. cials are tentatively planning more, but believe functional contracts have only limited application.
European Asphalt Study Tour 1990 PROPERTY NG COMPARED WITH HOT-MIX ASPHAIJT Hot-Rolled* SMA Porous Asphalt Asphalt Shear resistance -(-) ++ ++ Abrasion resistance + ++ (-) Durability + +(+) ++ -(-) Load distribution (-) (-) -(-) Cracking resistance + +(+) +(+) (-) Skid resistance 0 + +(+) Water spray 0 0 +++ Reflection + + +(+) Noise reduction 0 +++ Public recognition + ++ +++
* The hot-rolled asphalt is the British surface mix.
0 Means equal to the asphaltic concrete + Means better than asphaltic concrete + + Means much better + + + Means very much better - Means worse -- Means much worse --- Means very much worse Items in ( ) indicate a half mark
The large contractors--but not small Two large multinational contractors do contractors--seem to favor this type of about 85 percent of the asphalt pavement contract, but have some concerns. They business in Sweden. Each has trade would like the government to set less names for several of its products. demanding specifications. One major Whether or not patent rights or propri- contractor stated that functional con- etary rights were involved with any of the tracts provide an opportunity to empha- mix designs or mix processes was not size and measure the real quality of the clear. Swedish specifications are report- work. The current system, as the large edly open enough that anyone can com- contractors see it, often measures the pete, although the market dominance by exactness of theoretical recipes, rather the two major contractors makes market than quality. They also believe current entry for other contractors difficult. test methods are often unreliable and unrepeatable, a view that contractors in The two large contractors own and oper- the United States have expressed about ate the asphalt plant visited in Sweden. tests in this country. As in the rest of Europe, this plant and
European Asphalt Study Tour 1990 34 others in Sweden are not geared to high CONCLUSIONS production. The one visited could reportedly produce about 240 metric tons Stone Mastic Asphalt has the potential to per hour. The plant was equipped with a assist United States highway agencies in conveyor that introduces fibers into the solving some of the problems we have mix for SMA. The fibers are either had with HMA surfaces, at least in the cellulose or mineral, depending on which northern tier of States. The effect that contractor’s mix is being produced. To the higher temperatures in the South and make it easier to introduce cellulose Southwest would have on this mix needs fibers into the mix, pellets can be made further evaluation. The Swedish experi- consisting of 50 percent bitumen and 50 ence suggests several factors that will percent fiber. The bitumen and fiber can have to be kept in mind in deciding how be hauled in bulk and introduced into the SMA might be used in this country. It mix directly. The other fibers are must be placed on a sound pavement introduced into the ix in bags. structure. It requires premium aggre- gates. In addition, SMA is sensitive to variations in mix proportioning, so tighter controls in mixing and placement are necessary.
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DENMARK Items with the Highest Potential for to aging. The contractor also reportedly Implementation in the United States: used lime and cellulose fibers in the mix. This project required an S-year warranty. o Use of additives According to Road Directorate officials, o Contract administration procedures, Denmark is experiencing some problems including warranties with rutting. The country does not permit studded tires, so the rutting that does oc- o Bridge deck protection cur is caused by traffic--namely increased commercial vehicles and higher tire pres- sures. Pavements that have been in place ITINERARY for some time have, in recent years, started to rut. The Road Directorate is The Study Tour stayed in Denmark less using SMA-type surfaces to try to over- than 1 day. The stay included a visit to come this problem. Gap-graded HMA the offices and laboratory of the Danish with pre-coated chips rolled in has also Asphalt Pavement Association, a review been widely used. However, SMA of a paving project at the Copenhagen seems to hold the most promise for Airport, a briefing by officials of the a rut-resistant surface course. Danish Road Directorate, and a review of completed projects. Denmark requires a 5-year warranty on highway pavements covering smoothness, SUMMARY durability, and skid-resistance. The con- tractors select the mix design within the The paving project at the Copenhagen Road Directorate’s guidelines. The struc- Airport consisted of paving a taxiway. tural design was the responsibility of the The project was particularly well run. Road Directorate, not the contractor. The Two pavers operating side-by-side elim- contractor is responsible for routine test- inated any appearance of a longitudinal ing, with periodic checks by the Road joint in the wide mat. Seven rollers op- Directorate. Of the contract price, 5 per- erated behind the paver in a relatively cent is withheld during the warranty confined space. Carbon black was used period. as an additive in the mix (12-15 percent). According to contractor personnel, the Denmark seems to do more recycling carbon black makes the mix extremely than the other European countries, main- difficult to compact. According to the ly for environmental reasons although consultant, however, the difficulty is jus- economic benefits result, too. The coun- tified because the carbon black improves try’s road contractors reportedly recycle temperature susceptibility and resistance about 200,000 tons of HMA per year.
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Danish road officials emphasize bridge laid on the road at a distance commen- deck protection and claim considerable surate with the height of the dots, giving success with the process used. All bridge the driver the impression of an unbroken decks, whether concrete or steel, are line. Because of the height of the dots, covered by a protective system of four incidental light from headlights is bituminous layers ranging from a mem- reflected toward the driver, thereby brane seal to a chip seal wearing course. enhancing visibility, while the raised dots create a noise that alerts the driver when The Danish Asphalt Pavement Associa- the vehicle is leaving the roadway. tion’s laboratory is well-equipped and appears to be used mainly for testing CONCLUSIONS mixes and mix design. The tests basically give contractors a level of comfort with The problems Denmark is experiencing their designs--an important factor with its asphalt surfaces are similar to because of the warranty requirement on those in the United States, though not as all major highway projects. extensive. As in other countries, SMA shows great promise as a solution. The A Danish contractor demonstrated inno- Road Directorate is participating in the vative equipment for applying edgeline Strategic Highway Research Program, so pavement strips. The process is marketed perhaps mutual solutions can be found. as “Spotflex.” A machine applies dots approximately 3 mm high but can be any Contract administration features, width desired. The marking material con- including the warranty provisions, should sists of a two component acrylic resin be further studied for potential use in the used as a binder, glass beads, titanium United States. dioxide, and filling substances. They are
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GERMANY Items With the Highest Potential for United States freeway standards is Implementation in the United States: extremely difficult. Motorway pavement structures are designed for a 40-year life, o Splitmastixasphalt (SMA) as opposed to the 20 years often used in the United States. Surface conditions are o Drainage asphalt generally excellent, but some rutting and cracking was observed on a few sections. In general, the Autobahn network is a o Contract administration procedures mature system with many miles under rehabilitation, much the same as our ITINERARY Interstate system.
The German leg of the study consisted of Most major highways have a bituminous meetings with government and industry surface (71 percent of the Autobahns and personnel, a tour of the Federal Highway 99 percent of federal highways). The Research Center (Bundesanstaltfur main types of bituminous surface are Strassenwesen--BAST) near Bonn, visits Gussasphalt, SMA, and HMA. The to construction sites where activities Germans consider Gussasphalt to be ranged from laying HMA base to thin their most durable surface, followed by overlays and projects to fill ruts. Person- SMA and HMA. nel from all three levels of government (city, state and federal) were involved at Gussasphalt is a poured mastic mix with one time or another in the meetings and chips rolled into the mixture. It requires on-site reviews. special equipment, as well as quite a bit of hand work, and is placed at approxi- SUMMARY mately 425’ F. German officials use Gussasphalt on sections of the Autobahn The review in Germany concentrated on with the highest traffic volumes and on the Autobahns and major arterial routes. bridge decks.. The expected service life is The Autobahns are the main arteries of 12-18 years and it costs about 90 percent commerce in the German transportation more than HMA. system carrying approximately 30 percent of the traffic. Although trucks comprise Germany is given credit for inventing about 20 percent of the total, study tour SMA, which is used as a surface coarse on participants observed a much higher normal traffic sections of the Autobahn percentage of trucks on some sections. and on other major federal highways with high traffic counts. The maximum aggre- The Autobahns generally have 1940’s gate size used for SMA in Germany was geometry. Because of environmental smaller than in Sweden. In some cases, concerns, German road officials have a maximum size of 8 mm is used, but found that improving the Autobahns to 11 mm is typical. The grading curve also
European Asphalt Study Tour 1990 42 seems to be a little flatter than in Sweden. on it within a half-hour after it is laid. Asphalt cement content is relatively high Several States in the United States are (7 percent, plus or minus) and fibers are using this product. used as a stabilizer for the mastic. Sand is sometimes added to the surface to The Germans no longer do individual increase initial skid resistance. Expected structural designs for pavement projects. service life is 10-15 years. Typical structural sections have been Splittmastixasphalt, as SMA is known in developed for asphalt and PCC pave- Germany, costs 20 to 30 percent more ments on the basis of traffic volume and than HMA. Hot-mix asphalt is used as a classification. Mix designs are selected surface course on other Federal, state and the same way. These structural sections county highways. The expected service and designs are based on experience and life is 8-12 years. the Germans are not interested in any other approach. Because the Germans Porous asphalt is not yet in general use in do not tolerate frost or moisture prob- Germany. Because, however, of a strong lems in the underlying layers, they do not emphasis on noise abatement, PA may have to try designing the upper courses to become more common. German road compensate for inadequacies in the officials see it as having strong potential subgrade or subbase. They can base their for reducing noise as well as increasing design practices on the fact that the safety. They are looking not only to subgrade is structurally sound and reduce the noise caused by the adequately drained. interaction of tire and pavement, but to dampen traffic noise created from all Specifications seem to reflect a combin- sources. ation of method and end result. The contractor does the mix design within The Germans underlay the PA surface limits shown in the government’s recipes with a sealing membrane to eliminate for different mixes. The contractor also water intrusion into the structure. A does the quality control, but the govern- cross-section of one such project also ment does the quality assurance, either showed an underdrain system in the with its own staff or, most often, through existing pavement structure to take away private labs. Of the countries visited, the the water. This surface is limited to high German government appears to exercise velocity traffic areas because debris tends the most oversight of contractor to fill up the voids. Porous asphalt is operations. about as expensive as Gussasphalt, probably because of the requirement for Study tour participants observed major the membrane sealer and drainage. reconstruction on older sections of the Autobahn, but most work involved cor- A patented slurry seal process known as recting such surface problems as rutting Ralumac is being used with some success and skid resistance. The German pave- as a rut filler and thin overlay. The major ment engineering philosophy is to fix the advantage is that it will adhere to PCC problem before it occurs. As a result, and is quick setting. Traffic can be placed much of the work was on pavements that
European Asphalt Study Tour 1990 43 would be considered in good condition in A 4-year warranty is required on highway the United States. The Germans also contracts. On most projects, an amount believe in fixing only the existing prob- equal to 3 percent of the bid price is lem. If one lane is deformed or is losing retained during the warranty period. skid resistance, the Germans will mill off Whether this is a cash retainage or can be and resurface only that lane. Often, two bonded was not clear. The contractor is different mixes can be observed in responsible for any defects that occur adjoining lanes because one was during the 4-year period. In essence, he rehabilitated and the other was not. is responsible for maintaining the pave- ment while the warranty period is in Contracts are awarded to what the effect. Germans termed “the most acceptable bidder.” Time did not permit the study The sophisticated asphalt plant near tour participants to collect enough Hamburg was completely enclosed except information to determine how the for its 15 cold storage bins and its aggre- selection process works. In most cases, gate stockpiles. The plant has two dryer the contract reportedly is awarded to the drums, although it still uses a batch mixer. lowest bidder, but technical elements are One drum preheats the RAP, while the also considered. While bid documents other heats virgin material. Exhaust gas may specify the type of pavement (asphalt from the virgin drum, which has a burner, or PCC), the contractor can propose an goes through the other drum to preheat alternate type. This process appears to be the RAP. The plant is fully automated more like value engineering than and reportedly capable of producing 160 alternate bidding. different mixes. It routinely produces, however, only about 20. German asphalt For reconstruction projects, how the plants are not geared to high production, bidders propose to use recycled asphalt ranging from 160-250 tons per hour. pavements (RAP) is another technical Shared ownership of a plant by two or factor considered in the award. The more contractors is reportedly fairly contractor is required to recycle common. materials, to the highest level possible, on the project. For example, a contractor As in the other European countries, who demonstrated he could use 50 Germany has a large centralized research percent RAP in the binder course would facility. The BAST employs about 350 be favored over a contractor who planned people--more than twice the number at to use the RAP as subbase material or fill. the FHWA’s Turner-Fairbank Highway No RAP is permitted in the surface Research Center. The lab includes a course. Study tour participants could not full-scale pavement testing device, wheel determine how often technical factors tracking tests for rutting, and accelerated override cost considerations in awarding wheel wearing devices for evaluating contracts. Several large contractors seem tire-pavement interaction. Germany has to dominate the market, a situation that made a much stronger commitment than also exists in the other countries visited. the United States to research as a major part of the problem-solving process.
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The Germans are dedicated to protect- Prudent use of fibers and polymers can ing bridge decks and assuring good ride- enhance a mix, but cannot compensate ability. The noise levels of traffic on for poor mix design or poor materials. In bridges is also an important consider- Germany, as in the other countries ation. Bridge deck protective systems visited, premium crushed aggregate is seem quite expensive, but they are used where premium mixes are required. effective. The systems generally consist Hauling aggregate several hundred miles of an epoxy resin on top of the surface to or importing it from other countries is the be protected, followed by an asphalt seal rule rather than the exception. with a gussasphalt surface. Again, as in the other countries, quality CONCLUSIONS control by the private and public sectors in Germany appears excellent. Warranty For the United States, SMA has strong requirements are partly responsible. potential. While a 40 mm overlay seems Another major reason is the fact that each to be standard in Germany, thinner contractor has more responsibility than overlays with SMA are used, as are a contractors in the United States for mix smaller maximum size course aggregate. design, production, and laydown Gussasphalt, by contrast, does not have operations. strong potential for use in the United States. Factors working against the use of Warranty provisions should be given closer review to see if they would be Gussasphalt are its cost, special applicable in the United States. equipment requirements, and high Similarly, the provisions in the bid laydown temperature, which poses documents allowing the contractor to potential air pollution problems. submit alternate solutions should be examined.
European Asphalt Study Tour 1990
ITALY Items With Highest Potential for with in the United States, and may seem Implementation in the United States: complicated by comparison. Following World War II, the Italian government System of concessionaires to build established a new national highway motorways agency to reconstruct the nation’s war- damaged highways. That agency evolved Contracting procedures into today’s ANAS, which operates au- tonomously, with the Italian Minister of Public Works serving as Chairman. The Use of modifiers and additives ANAS is responsible for overall highway planning in Italy and works to bring high- Pavement management system ways to both wealthy and poor areas.
ITINERARY In the early years after World War II, Italy concentrated on repairing its A subcommittee of AASHTO and damaged highways and bridges. In the FHWA study tour participants visited mid-1950’s, development of a major Italy for one evening and a full day. The motorway network began. The Italian group toured several installations, includ- government, short on resources, decided ing the headquarters of the National that the best way to build the motorways Road Board (Azienda Nazionale was to grant concessions to private com- Autonoma delle Strada--ANAS), an panies. They would design and build toll asphalt plant using the Novophalt process motorways and operate them for 30 years, and a section of motorway where the before turning them over to the govern- modified asphalt was being laid, and a ment. In addition to providing a mech- restaurant concession operated by anism for using private capital, this Ferretti at the FZaminia Est Highway arrangement had the advantage of allow- Service Area north of Rome. During a ing the concessionaires to avoid the bid- visit to the Societa Autostrade Laboratory ding procedures normally used by ANAS at Fiano Romano, the subcommittee for letting construction contracts. The learned about Italian highway engineer- concessionaires, being wholly responsible ing and asphalt technology, as well as the for the motorways under their control, process and equipment used to manage are free to negotiate contracts as private pavements on the motorways the businesses. company controls. Today, ANAS is directly responsible for SUMMARY some 50,000 km of state highways and roads, including about 1,000 km of toll- The ownership, management, and free motorways. The agency also super- operation of the Italian highway system is vises the network of concessionaires and quite different from what we are familiar may make capital contributions toward
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concession toll roads. It does so when a In several ways, Societa Autostade is concessionaire is constructing a motorway similar to toll authorities in the United in a depressed area where toll revenues States. The company has a large may not be sufficient. In all, 27 conces- engineering staff and a well-equipped sionaires manage 6,000 km of Italy’s 7,000 laboratory in which development was km of existing or planned motorways. observed to be underway on several new ideas in pavement technology. Tolls Societa Autostrade, which received the generate a healthy revenue, with ANAS first concession for a motorway in 1958, observing that typically, the Italian con- controls some 3,000 km of the motorway cession companies have maintenance network. The company is part of a corp- funds available that are “five/six fold orate structure that goes back to the post- higher than” funds available to ANAS. war period when capital was short and the Italy, like toll authorities in the United country needed to reestablish its private States, uses concessions for the operation industrial activity. One method used to of restaurants and other service facilities overcome these problems was creation of on its toll roads; the one visited by the large private companies funded mainly subcommittee was excellent. According with public money. The giant Institute to Societa Autostrade officials, nearly for Industrial Reconstruction, known as 25 percent of the company’s operating the IRI Group, is one of these companies. revenues are generated by the service It includes many subsidiary corporations facilities or the leasing of excess land at in a variety of fields. Within the IRI interchanges. Group is the IRI-INTALSTAT Group, which includes Societa Autostrade. In Italy today, the highway and road system carries 85.4 percent of all passen- Another IRI-INTALSTAT Group gers and 61.5 percent of all goods move- company, PAVIMENTAL S.P.A., is the ments. Highway traffic growth has been contractor for construction and mainten- high in recent years, with Societa Auto- ance of motorways under concession to strade reporting a 45.4 percent increase IRI-INTALSTAT. Similarly, the group’s on its motorways between 1984 and 1989 BONIFICA is a civil engineering consult- (47 percent for passengers, 40 percent for ing company that works for Societa Auto- goods). In 1989 alone, the company saw stmde. This is a greatly simplified descrip- a 7.6 percent increase (7.2 percent for tion of a complex array of relationships passengers, 9.1 percent for goods). developed over several decades. In ess- ence, though, Societa Autostrti differs Societa Autostrade’s concessions were from United States toll authorities in its recently extended and now run to 2018. ability to negotiate contracts for work by Since the concession started in 1958, the what are, in effect, related companies extension means the company will be with overlapping ownership and direc- responsible for some motorways for tors--and with no apparent use of about 60 years. This realization, and the competitive bidding. desire to reduce maintenance costs and thereby increase net revenue from tolls, caused Societa Autostrade to establish a
European Asphalt Study Tour 1990 49 comprehensive pavement management Deep repaving is done with base course system. It includes a twice-yearly struc- polymer-modified asphalt mixes, some- tural examination of all 3,000 km of its times at night. The old asphalt mix is motorways. The company reported that cold-milled and recycled in place. Then its system has resulted in an overall cost a non-woven fabric is placed, followed by reduction of around 30 percent because the laying of a polymer-modified asphalt of a more intelligent use of maintenance base course and asphalt mix binder and activities. wearing courses.
The Societa Autostrade pavement Poly-functional composite pavements management system tries to reduce all are just being introduced. They are being factors to numbers, which are then considered for future reconstruction of compared with pavement performance all motorways. One has been placed on curves to design specific maintenance the Fiano-S. Cesareo connector. It com- activities. The analysis devices have been prises a continuously reinforced concrete phased in over the years, and now include pavement (CRCP) course laid on a a SCRIM skid resistance truck (1982), a graded aggregate base and covered with falling weight deflectometer (1983), an an open graded drainage course of ARAN truck for measuring profile and asphalt concrete. The CRCP provides geometric characteristics (1985), an APL resistance to fatigue, while the wearing device for measuring the longitudinal course is considered as a renewable profile (1988), and a newer truck, known surface that has high skid resistance and as SUMMS, for measuring skid resistance reduces water spray and rolling noise. and texture. The machines take measure- ments at different intervals and operate at The subcommittee visited an asphalt different speeds, as follows: ARAN, 20 m plant that produces a modified asphalt by and 60 km/h; APL, 25 cm and 72 km/h; the Novophalt process. It blends used and SUMMS, 10 m and 60 km/h. The polyethylene scraps, in this case from falling weight deflectometer stops for 10 ground electrical insulation, into the measurements every km, with one minute asphalt cement. While costs increase per measurement. substantially with the Novophalt process, the pavement reportedly might last more Societa Autostrade has placed pavement than twice as long. maintenance activities in six categories: reinforcing, surface dressing, milling and At the same plant, the subcommittee repaving, deep repaving, recycling in examined two asphalt recycling pavement place and at plant, and poly-functional trains owned by PAVIMENTAL. The composite pavement. The company is exhaust of one train was coated with increasingly using open-graded bitumi- asphalt, indicating a possible problem nous mixes, both to reduce rolling noise with substantial operating emissions. and hydroplaning, and does considerable Another machine is being modified for recycling. operation in the Soviet Union.
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The subcommittee was told about Italian CONCLUSIONS asphalt practice, which includes exten- sive use of such modifiers as polyethylene The Italians have amply demonstrated and rubber (the fact that the rubber was that toll authorities can construct and not from tires was emphasized). The maintain a modern motorway system, aggregates used in Italy are usually either although the specific institutional basalt or limestone. In a basaltic base arrangements used in Italy seem unique course, asphalt content will typically be to that nation’s situation. Sociefa Aufo- about 4.5 percent. The second course sfrade’s pavement management process may use limestone, with about 5.2 per- and some of its highway engineering cent asphalt and 3-4 percent voids. The developments, such as its proposed use typical wearing course has aggregate in of composite pavement, are worth further the 10-15 mm range, with an asphalt con- study. tent of about 6 percent and 2-3 percent voids. However, for drainage or PA wear- ing courses, aggregates average around 18 mm, with an asphalt content of about 8 percent and 22 percent voids.
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FRANCE Items with the Highest Potential for the eight concessionaires involved, seven Implementation in the United States: are quasi-public entities (public-private partnerships) and one is fully private. A o Patented additives and polymer- three-person commission representing modified binders the Ministries of Transport, Finance, and Development selects the concessionaires, o Contract Administration Procedures whose contracts are for 35 years and can be renegotiated. A 5year warranty is required. The concessionaire sets toll o Well-equipped laboratories, both rates, with the approval of the Finance government and private Minister. o Thin overlays and surface treatments France uses more polymer-modified asphalt than the United States and prob- ITINERARY ably uses more than any other country in Europe. In fact, France reportedly In France, the study group’s travel was uses more than half the polymer sold in mostly by air and rail, rather than by Europe. Approximately 7 percent of motor vehicle as in the other countries. all asphalt mixes used in France are The trip included a tour of the Central polymer-modified, but the polymers are Laboratory of Bridges and Roads used only in the surface course. The (Laboratoire Central des Ponts et comparable figure for polymer-modified Chausees--LCPC), the main laboratory asphalt in the United States is 2-3 per- of the Ministry of Public Works in cent. Polymer-modified binders cost Nantes. Most government-sponsored about twice as much as standard asphalt civil engineering research and develop- cement and on average, the mix is ment occurs in the laboratory. The 2-day approximately 20 percent more tour was rounded out by tours of active expensive. and completed projects in the vicinity of Nantes and Lyon as well as visits to con- More patented or proprietary mixes, tractor facilities and laboratories. The additives, and processes appeared to be work underway generally consisted of thin in use in France than in the other coun- overlays and slurry seals. tries visited or in the United States. Each large contractor the study group met with SUMMARY had several. In some cases, the products were developed by government-industry France has approximately 7,000 kilome- cooperative ventures. Some of the prod- ters of motorways comparable to our ucts are marketed and used in the United Interstate System. Most are toll facilities States. designed, built, and operated by conces- sionaires (about 6,000 kilometers). Of
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Overall, in fact, the French system 1. Conventional hot-mix road base--This encourages innovation by giving con- mix, which is 120 to 180 mm thick, is tractors the opportunity to use their placed in a single lift. Maximum size own technology in pavement design and aggregate is 20 mm and all aggregate construction. For example, specifications is crushed. It contains approximately usually identify desired end-results. 4.2 percent asphalt, which has either While many patented additives and pro- 40/50 penetration or 60/70 penetration. cesses can be used in the six basic mixes described below, contractors may propose A variation of this x-nix is high modulus other solutions--and the contracting road base, which contains 6 percent agency often accepts them. The proposer asphalt with a lo/20 penetration and a of an innovative solution, however, must polyethylene additive. The French claim be able”to demonstrate to the owner’s a 25-40 percent thickness reduction for satisfaction that the desired results can the same structural effect with the high be achieved. This public-private cooper- modulus mix. ative approach seems to result in superior products and superior pavements. 2. Conventional HMAconcrete--This is used in new construction and for over- The study tour members observed a lays. Thickness is 60-80 mm while the particularly unique patented operation maximum size of aggregate is 14 mm for used to produce a stress absorbing mem- the thicker lift and 10 mm if the lift is brane (SAM). The operation consists of a 60 mm. Only crushed aggregate is used. modified binder strengthened by contin- It is continuous-graded, with 30-35 per- uous synthetic organic threads spread cent passing the 2 mm sieve. Asphalt over the binder and covered by chips. content is 5.7 percent of 40/50 penetra- The unusual feature was that the binder tion or 60/70 penetration with 5 percent and the threads were distributed by the plus or minus voids. contractor’s patented machine. Large reels were mounted on the back of this 3. Thin asphalt concrete--This mix is used machine and the threads were dispersed for overlays of approximately 40 mm. over the binder in a single operation. A It’s a gap-graded mix with a maximum conventional spreader following the other aggregate size of 10 mm using 100 per- piece of equipment distributed the chips. cent crushed aggregate. Asphalt content The result seemed to be similar to fabrics is 5.7 to 6 percent using a 40/50 penetra- embedded in a sprayed binder. It’s obvi- tion or 60/70 penetration. The French ously an expensive operation but the con- claim excellent rut resistance and skid tractor claimed it was successful. Other resistance with this mix. contractors reported that they had their own less expensive version of a SAM that did not include the threads. 4. Very thin asphalt concrete--This mix, which is used for overlays of approxi- mately 25 mm, is similar to the thin The government specifies six basic classes asphalt concrete just described. The of hot-mix for use in France: differences are that the binder is modi-
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fied with polyrners, rubber, or fibers and is similar in concept to the FIIWA’s ALF the asphalt cement content can go up (Accelerated Loading Facility). The to 7 percent, depending on the modifier loading wheels of LCPC’s facility rotate used. In addition, a heavy tack of in a circular pattern from a fixed center polymer modified emulsion is used. point at a speed of 70 km/hr, adjusted from 8 to 18 metric tons, with either 5. Porous asphalt--This mix is similar to single- or dual-wheel configuration. the open-graded friction course used Laboratory officials reported that a in the United States and the PA and 20-year load for a typical major highway drainage asphalt used in other European could be achieves in about 2 months. The countries. It’s a gap-graded mix with a facility has three separate tracks that maximum aggregate size of 14 mm and a allow for continuous testing while new 22 percent void content. The thickness structural sections are constructed. is 40 mm or less. In most cases, a modi- fied binder of polymer, rubber, or fibers Another unique feature of the LCPC is used. complex was the equipment testing area. Part of it is dedicated to testing such 6. Paver laid chip seal--The LCPC and a equipment as pavers and finishing mach- private contractor developed this rel- ines for speed, vibration, accuracy of atively new product. It’s approximately control, etc. Another part of the facility 15 mm thick. The binder layer is a tests mixers for speed of production and polymer-modified emulsion and the chips measuring accuracy. A unique feature are between 6 and 10 mm, pre-coated hot was an attempt to use electronic screen- with sand and asphalt. This mix, which is ing with an optical readout to check grad- used only on pavements that are not ation. If such a feature became opera- deformed, is intended to improve surface tional, it would‘significantly improve characteristics. A special paver was also plant operation by permitting accurate developed to lay this material. and consistent batching.
France does not use SMA, which has pro- Some of the equipment used in mix duced excellent results in other European design and verification was of a type not countries. The chief concern is reported- generally seen in the United States. The ly the difficulty of achieving the desired gyratory compactor, the pneumatic-tire micro-texture for skid resistance. compactor, the rolling wheel rut tester, and the fatigue equipment were particu- larly impressive. The LCPC developed The LCPC laboratory at Names is the flagship of the public works laboratories much of the equipment, which private network, which includes an additional 17 concerns manufacture and distribute regional laboratories. In all, the network under exclusive licenses. employs about 2,700 people. The LCPC alone employs about 580 people, of which Laboratories operated by the major con- 200 are engineers. The lab includes a tractors are also well equipped, generally full-scale accelerated testing facility that with the LCPC-designed equipment. One result is that the contractors are
European Asphalt Study Tour 1990 highly confident when testing their mixes ernment requires top quality aggregate because the government will use the same and sophisticated surface mixes. Recycl- model of equipment and the same tests. ing occurs, but the recycled asphalt pro- Agreements on test procedures to be duct is never used in the surface courses. used to predict performance of propri- etary products were worked out after CONCLUSIONS private/public sector discussions over 2 years. The United States should try the French approach to mix design and the equip- As in the other countries visited, several ment used as tools to verify the designs in large contractors dominate the market. the laboratory. French testing simulates Contracts are generally awarded by the real-world performance of the pro- competitive bid except for motorway ducts. Several of these concepts and construction. As mentioned previously, some of the equipment are being evalu- motorway construction contracts require ated by the SHRP. The private sector a 5-year warranty, but on other highways, accepts the results because of the exten- the warranty is for 1 year. sive public/private dialogue and the evaluation of testing approaches before All bridge decks were sealed with asphalt adoption. material for protection and to improve rideability. Several patented processes France is far advanced in the use of for this purpose would be worth looking polymers and modified binders. These into for use in the United States. mixes are used judiciously and, seem- ingly, successfully. An in-depth study of Another similarity with the other coun- the French experience should be under- tries visited was the fact that hot-mix taken for possible application in the manufacturing facilities are not geared to United States. high production. Because of the sophisti- cated surface mixes used, the facilities arc The cooperation between industry and designed more for quality and uniformity. government in France fosters innovation. Shared ownership of plants by two or The institutional relationships are differ- more contractors is reportedly fairly ent from those in the United States, but common. some techniques could be borrowed for use in this country to promote closer The emphasis in France is on preventive government-industry cooperation. The maintenance. The government promotes result would be a higher quality product. innovative solutions. In addition, the gov- ..::. . :.:.:.,...... xc.:.:...... ,.:::: jj j j. . . . .A. . . .: j ......
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UNITED KINGDOM Items With the Highest Potential for The study tour participants reviewed Implementation in the United States: work on the Motorway system, including major reconstruction on the M-l motor- o Heavy Duty Asphalt Bases way and new construction for an exten- sion of the M-40. The extension was the only major construction on new location o Pavement Management Equipment that was observed during the European trip. In Europe, as in the United States, o Contract Administrations Procedures construction on new location is rare (Lane Rental) because of environmental concerns and the high cost of right-of-way acquisition. o University Highway Research Program On the M-l, the existing structure con- ITINERARY tains 340 mm of asphalt on a limestone subbase. The structure has 200 mm of The itinerary in the United Kingdom macadam base, 60 mm of HRA base (U.K.) consisted of a tour of the labor- course, 40 mm of HRA wearing course, atory at the University of Nottingham; a and an overlay of 40 mm of HRA, which review of active construction projects, was put down in the early 1980’s. The where activities ranged from placing reconstruction project varied from HMA lower base course to surfacing with complete replacement of the full-depth HRA; a discussion with government and asphalt pavement structure in the outer industry officials at the Transportation lane, where truck traffic is heavy, to Road Research Laboratory (TRRL); a milling and replacement of the upper tour of the TRRL facilities; and a visit to base and/or wearing course on the other a completely enclosed production facility. lanes.
SUMMARY The new structural section consists of approximately 380 mm full-depth asphalt In the U.K., the federal Department of construction over the same limestone Transport is responsible for approxi- subbase--40 mm of HRA wearing course, mately 4 percent of total road mileage. 215 mm of upper road base, and 125 mm This 4 percent, which consists of 1,600 of lower road base. This design is the preferred pavement structure for high- miles of Motorway (equivalent to the Interstate System) and 5,000 miles of volume motorways in the U.K. It is based on a 40-year design, with planned surface trunk highways, carries approximately 30 percent of all traffic. Approximately replacement in 20 years. 90 percent of all roads are surfaced with asphalt. The unique feature of this section is that the highest strength lift is the lower road base. It is a gap-graded mix with a
European Asphalt Study Tour 1990 60 maximum size aggregate of 40 mm and The plant visited, which was not invol- an asphalt content of 5.7 percent--50 pen ved in either project, included 13 aggre- asphalt cement was used and 60 percent gate storage bins and 28 cold feed bins. of the aggregate was larger than 2 mm. It was unique because it was completely The base is designed for stone-on-stone enclosed, having been built in an existing bearing with no specified density require- building (50 by 240 meters) to satisfy the ment. It has high tensile strength and is concerns of the surrounding community. fatigue-resistant and waterproof. While the plant looked neat from the outside, the interior was noisy and dusty. The upper road base is a dense-graded It has a capacity of 600 tons per hour and bituminous macadam. The maximum size is expected to produce 650,000 tons this aggregate is 40 mm with approximately year. The owner of the plant hauls aggre- 3.7 percent of 50 pen asphalt cement. gate in from his own quarries on trains that he also owns. He has several other The surface or wearing course was a plants in the area, all of which are drum HRA gap-graded mix with a maximum mixers, in contrast to what was observed aggregate size of 14 mm and 7.9 percent in the other countries visited. of 50 pen asphalt cement. This course is unique because pre-coated chips are Incidentally, this company regularly ships rolled into the surface to enhance skid granite aggregate to Houston, Texas, at a resistance and improve drainage. The reasonable price of $6 to $8 per ton. The chipping operation is labor intensive, with cost can be kept relatively low because three laborers following the spreader to the aggregate is used as ballast when make sure chips are evenly distributed. It ships hauling grain to Europe return to is similar to the so-called sprinkle mix Houston for a new load. that was tried briefly in the United States several years ago. United Kingdom offi- Additives are not used extensively in the cials, who claim the chips do stay imbed- U.K. as yet. Only one, natural rubber, is ded and are not a hazard to windshields, found in the specifications. Officials are are satisfied with this HRA surface researching such other additives as poly- course. mers and manganese and are trying to develop a functional specification. Now, On the M-40 new construction project, when additives are specified, it is by trade the structural section varied slightly in the name and, as in the United States, U.K. thickness of the base course layers but officials do not favor this method. The followed the same principles. use of polymers is reportedly increasing, but EAST participants did not learn if The HMA manufacturing facilities in the polymers were in any of the mixes they observed. U.K. seemed geared more toward pro- duction than those in the other countries visited. On the M-l and M-40 projects, The mixes are basically recipe mixes the contractor was laying about 5,000 except that surface mixes are reportedly metric tons per day from three plants. designed. As was observed in Germany and France, a large number of mixes are
European Asphalt Study Tour 1990 61 in use throughout the country. Only a few either party). The contractors’ concerns basic mix designs are used, but the many are that this system would create another specifying agencies (all levels of Govern- level of oversight, with resultant added ment) add their own twists to the recipes. paperwork, and that the specifications The plant visited by the EAST partici- and test procedures are not precise pants reportedly produced 158 types of enough to impose such a system. mixes last year. In the U.K., a “lane rental” contract is New specifications are being developed used on sensitive projects where the to identify a small number of “preferred project must be re-opened at the earliest mixes” for various applications in the possible time. This type of contracting is hope of reducing the large number of being used on 25 to 30 projects a year. mixes in use today. Generally, current Three types of lane rental contracts have specifications are of the method type. In been used: the revised version, U.K. officials are striving more for end-result or end- 1. The contractor’s bid includes the cost product specifications. One factor moti- of the work and the time he needs to vating U.K. officials to revise the specifi- complete it. The bid with the shortest cations is a concern about what will completion time becomes the base. The happen when EC 92 comes about and government adds whatever the pre- each country has different specifications determined daily incentive is to the other and testing procedures. They believe that bids proposing longer times. The low all the countries of Europe should move bidder is then selected on the basis of cost towards comrnon end-result specifica- to do the work plus time to complete it. tions and common testing procedures. On the M-l reconstruction project, for example, the incentive/disincentive was Warranties, per se, are not required in 25,000 pounds sterling per day, the the UK; however, the contractor must highest amount allowed by the Depart- maintain the project for 1 year, after ment of Transport. If the contractor which any needed corrections are made completes the work in advance of the and it is given final acceptance. During total days he specified, that amount is that time, 1.5 percent of the contract cost his daily bonus. If he goes beyond the is retained. specified time, he is penalized a like amount. Officials in the UK would like to move to the quality assurance/quality control (QA/ 2. The contractor pays a pre-determined QC) concept. The contractors seem to daily rate for the site. The quicker he favor it but are leery of the third-party gets in and out, the less his rental pay- concept being advanced by some advisors ment is. and consultants. Under this concept, an independent third party would have the final say-so over the quality of the work. The third party might be an engineering society or a consultant (not retained by
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3. In a true lane rental arrangement, the As in the other countries visited, several contractor pays a daily rate for the closetil contractors dominate the market. None lanes. This, again, is a pre-determined of the contractors who met with the amount. Obviously, the fewer days the EAST participants expressed discomfort lanes are closed, the less he pays. with the RFP process and all supported the lane rental contract approach. The first option, which has been adopted as standard, is a variation on the incen- Some of the contractors’ concerns, tive/disincentive clauses used in some however, are similar to those heard in the States in the United States. The varia- United States. They claim the process tion--sometimes referred to as A + B type involves too much paperwork and too contracting--has been tried in several much bureaucracy. Further, problems States as well. The lane rental concept or often occur in getting decisions on a proj- incentive/disincentive concept is only ect. To solve this problem, the contrac- practical if a large degree of certainty tors would like an experienced project exists on the scope of work. If several engineer on the project, full-time, with structures are involved or if completion decisionmaking authority. According to depends on completion of an adjoining some contractors, contract lettings and section by another contractor, the con- funding involve too many peaks and cept is not used. Officials stated that a valleys. Moreover, contractors would like change order on a lane rental project is more control over the work, preferably essentially a blank check. The other two using the QA/QC system, and recom- types of lane rental contracting are no mend the U.K. consider adopting the use longer used in the U.K. of warranties, as in the other countries of Europe. Government officials are look- On a large project, the government uses a ing into it, but they are just not ready to request-for-proposal (RFP) process to go into warranties now. In this area, as in select a contractor. An advertisement is others, concerns exist because of EC 92. published inviting solicitations of interest. The other countries in Europe require The responses are short-listed, normally some type of warranty and give contrac- to six contractors but the number can tors more control over projects. range from as low as four to as high as seven. The selected contractors are The pavement research group at the invited to submit detailed proposals University of Nottingham has been in (bids). The contractor who submits a existence since 1954 and handles research technically acceptable proposal with the as well as technology transfer. Officials lowest cost will be awarded the contract. and staff members see bridging the gap Naturally, if the project involves a lane between research and development work rental contract, the time and cost to do and practical technology as one of their the work will determine which contractor main missions. They have received fund- is selected. ing from industry (oil companies, contrac- tors, suppliers, and consulting engineers), U.K. government agencies, and United States agencies (the Army, Air Force,
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SHRP, NAPA, and NCHRP). They are The machine to measure deflection is, affiliated with a private consultant and in essence, a mobile Benkelman Beam. contracting firm with offices on-site. The The equipment consists of a truck with private contractor plays a major role in Benkelman Beams, which are mounted technology transfer. Current major on opposite sides of the vehicle in front of activities include asphalt mix design, the rear wheels, and equipment inside the reinforced haul roads, asphalt vehicle for recording and analyzing data. modification, pavement foundations, and The measurement cycle includes lowering structural evaluation. the beams, rolling the vehicle forward while measuring the deflection, and The lab has a pavement test facility that is then lifting the beams. In the U.K., 17 about 5 meters long and can test a pave- machines of this type are in use and the ment that is 1.5 meters deep. The test Motorway system is measured every pavement is loaded by a wheel with a 3 years. loading capacity of 1 ton. It applies a single-direction load with a realistic dis- A standard, trailer-mounted Falling tribution of transverse variation in the Weight Deflectometer (FWD) is used for actual wheel path. Other smaller scale more detailed analyses of the pavement. wheel-tracking devices for fatigue tests Personnel of TRRL are experimenting are also in use. The staff has done some with ground radar to determine pavement work on correlating field performance condition and they think this approach with the various laboratory tests but can- looks promising. Some work of this type not fully validate the results. They are is also underway in the United States. working on this. Validation is, of course, a common problem for virtually any lab in A high-speed road monitor is used for the world. If the pavement research overall condition survey work. It uses group can overcome the problem, it will lasers as the detection system. The first be a major step forward. version, a trailer, is in routine use. The newest version is self-contained and The TRRL is the flagship facility for road incorporates television survey equipment research in the U.K. It is involved in similar to that used by SHRP. This research in all three elements of the high- device can measure rutting, cross-slope, way system (the highway, the vehicle, and grade, curvature, and microtexture. It is the driver). The equipment used for used more on the rural and lower-order pavement management at TRRL was of systems because it can be operated at particular note. While the equipment high speeds and generally gives sufficient itself may not be unique, what was unique information rapidly to determine if was the fact that it is used in the decision- improvement is needed. making process. Certain readings on pavement condition act as a “trigger” to A considerable amount of human factors initiate improvements. research has been done at a TRRL test track. The diverse subjects covered include the noise impacts on occupants of
European Asphalt Study Tour 1990 64 a house adjacent to a roadway, the accept- A noticeable difference is that little ability of a driverless bus, and the effect litigation is involved in government/ of alcohol and drugs on the driver. contractor disputes. They are usually settled administratively, as they are in the CONCLUSIONS other countries visited. Often, in fact, when EAST participants asked about lawsuits, the government and industry The public/private partnership is not as people looked perplexed because they pronounced in the U.K. as in the other were surprised to learn that in the United countries visited, except in the research States, claims are commonly settled in area. Particularly noteworthy was the court, rather than administratively. In public/private partnership at the Univ- general, the adversarial relationship that ersity of Nottingham. It appears to be an exists in the United States does not exist efficient, effective approach to problem Europe, so government and contractors solving and to basic research. More of seem able to work things out much better. this type of partnership may be on the They are not litigious societies. horizon in the United States if the con- cept of University Research Centers takes hold. Some barriers will have to come Large Scale Pavement testing devices are down and some effort will be required for used in most of the countries visited, as this concept to be accepted in the United well as in other European countries. States, but experience in the U.K. sug- Calibrating these machines, one against gests it can work. the other, would admittedly be a major effort, but would seem to be worthwhile. If the machines were calibrated, research Practices in the U.K. seem similar to the in one country would have more credi- United States in many ways. These bility in the other countries. This sharing include method specifications, contract of research would help forge a stronger administration (except, of course, for the bond between the countries. It might also RFP process), pavement designs, the NIH represent a substantial savings in that the syndrome (Not Invented Here), and same problem would not have to be industry objections to government solved over and over again across the oversight, red-tape, and paperwork. country or state borders.
European Asphalt Study Tour 1990 INNOVATIVE ASPHALT TECHNOLOGY 67
INNOVATIVE ASPHALT TECHNOLOGY
POSSIBLE USES OF EUROPEAN TECHNOLOGY IN THE UNITED STATES Conventional, continuous-graded mix groups, and individual paving contractors designs similar to those employed in the and bitumen producers in each country. United States are used in Europe for At these laboratories, the group discussed construction, maintenance, and rehabili- design features of the special-purpose tation. All the countries visited by the mixtures, pavement design parameters, EAST, however, make extensive use of and advanced test methods and labor- special-purpose mixtures, particularly in atory equipment for measuring the mech- surface courses, to enhance the perform- anical properties of asphalt mixtures. ance of high-volume pavements. These mixtures are designed to control rutting This chapter mainly reports on the and other distress under very heavy vol- special-purpose mixtures. It is based umes of truck traffic. Many of these mix- primarily on the observation of pave- tures rely on modifiers to help achieve ments, both in-service and under con- the enhanced level of performance struction, incorporating them. A site visit needed. report (SVR) was prepared for each observed pavement feature. The SVR’s Much of the EAST’s time was spent are presented in appendix A. In addition, examining these novel, special-purpose the observations of the EAST members mix designs. Members inspected 27 field were employed in preparing this chapter, pavements incorporating the mixtures supplemented by substantial and invalu- “on the ground” in Denmark, France, able written and oral technical informa- Germany, Sweden, and the United King- tion provided by the relevant road auth- dom. They also examined the operation orities, paving contractors, and material of hot-mix plants producing these mix- suppliers. tures in Germany, France, Sweden, and the United Kingdom. Further, they rode In assessing the significance of the asphalt over almost 1,200 miles of Interstate-type technology discussed in the following pavements in the company of personnel sections for the United States, the EAST from road authorities, paving contractors, members kept several factors in mind. and material suppliers who provided ex- First, European practice stresses regular tensive commentary on the design, con- maintenance of asphalt pavements to struction, maintenance, and performance slow or prevent distresses, particularly of pavements incorporating these special- rutting and fatigue and low-temperature purpose mixtures. cracking, that result from climate or an increase of traffic. Much of the mainten- The EAST also visited research and ance and rehabilitation is carried out on operations laboratories belonging to pavements with little or no visible national road authorities, contractor trade distress. These activities, including
European Asphalt Study Tour 1990 68 overlays and more substantial recon- Employment of these mixtures in the struction, are performed on a schedule or United States will probably require a are triggered by the results of periodic similar strict attention to materials quality. deflectometer or other instrumental measurements. This maintenance work is Fourth, typical traffic volumes, vehicle especially useful because all the high- mixes, truck weights, and tire pressures performance pavements observed appear are equal to or exceed those found in the to have been placed on foundations that United States. The special-purpose mix- were in very good condition. tures were observed almost exclusively on heavily-trafficked routes comparable to Second, the climatic conditions in the the United States Interstate and primary five countries are not as wide-ranging highways. Moreover, four-lane motor- as those found in many regions of the ways are still common in Europe in situ- United States. In particular, the high ations where practice in the United States summer temperatures prevalent in much would dictate six- or eight-lane roadways. of the United States are uncommon in Thus, traffic demand on each lane of Denmark, Germany, Sweden, and the these special-purpose mixtures is com- United Kingdom. Therefore, care must parable to that generally experienced in be taken in translating technology em- the United States. ployed in these regions to areas of the United States with markedly different Fifth, and last, European HMA pro- climates. duction almost universally employs batch plants. The technology observed has been Third, these special-purpose mixtures used rarely, if at all, with drum mixers, often employ select materials. Hard, which are common in the United States. low-penetration grade bitumens’ are As a result, transferring the technology to routinely used. For the coarse aggregate, United States practice will require care- specifications often stipulate 100 percent ful consideration of possible changes crushed stone or rock, which may be necessitated by the differences in produc- transported hundreds of miles across tion methods. Typical European HMA national borders to obtain the correct production rates are much lower than petrographic properties. Manufactured those attained in routine United States sands and limestone fillers are generally operations. This circumstance should also required. Such modifiers as crumb rubber be weighed in evaluating the applicability and polymers are also frequently used. of these technologies to United States practice.
1 In conformity with European practice, the term “bitumen” will be used herein in place of the United States term, “asphalt cement.” In this context, the European term “asphalt,” as used in PA or SMA, generally denotes an asphalt aggregate mixture or the United States “asphalt concrete.”
European Asphalt Study Tour 1990 69
STONE MASTIC ASPHALT
General Descritdion Netherlands, and Scandinavia as an overlay or surface course to resist load- In the opinion of the EAST members, the induced rutting and studded-tire damage. special-purpose mixture with the greatest promise for use in the United States is Select materials are usually employed in SMA. It was developed in the 1960’s in SMA construction. A hard, low-penetra- Germany as an overlay especially resist- tion grade of bitumen is used. It is modi- ant to studded tire damage. The term fied by the addition of cellulose fibers, splittmastrjcasphalt is used in the German mineral rock wool or, less often, polymers Supplemental Technical Specifications and to prevent drainage of the mortar off the Guidelines on Asphalt Sulfate Courses coarse aggregate during pavement con- (Zustzliche Technische Vertragsbedi ng- struction. The coarse aggregate is typic- ungen und Richtlinien fur den l3au von ally 100 percent crushed rock or stone. Fahrbahndecken aus Asphalt, abbreviated The sand fraction contains a large amount ZTV bit-StB 84, published by Der Bun- of manufactured crushed sand that may desminister FGr Verkehr, 1990 revision). be washed if it contains an unacceptable This term is variously translated as “stone- amount of fine particles. filled mastic” or “grit mastic asphalt.” (In the former East Germany, it was aptly To provide resistance to rutting and termed “skeleton asphalt”). Today, SMA studded tire damage, SMA relies on a is widely employed in Germany, the stone-on-stone skeleton. The point-
DENSE GRADED PAVEMENT STONE MASTIC ASPHALT
European Asphalt Study Tour 1990 70
FIGURE 1
100 oUSHM4 90 80 70
-0.05 .l 1 10 15 SIEVE SIZE, mm to-point contact achieved in the stone tions, but typical parameters have emer- skeleton provides an internal friction ged. The coarse material (retained on throughout the overlay that resists load- the 2 mm sieve) makes up 70 to 80 per- induced shear. The stone skeleton is filled cent of the weight of the aggregate; the and held together with a mastic composed top size of the coarse aggregate may of the bitumen, the sand fraction, and range from 5 mm to 22 mm., but is typi- aggregate fines. The mastic is bitumen- cally between 11 and 16 mm. Filler mat- rich and voidless so it provides a durable erial (defined as passing the 0.09 mm surface that is resistant to cracking. The sieve) accounts for another 8 to 13 per- stone skeleton must accommodate the cent of the weight. The sand fraction, mastic without disrupting the point-to- comprising the material sized between point contact of the coarse aggregate 0.09 and 2 mm, makes up only about 12 particles (those retained on the 2 mm to 17 percent of the aggregate’s weight. sieve) or the overlay will be susceptible to Figure 1 presents a typical 11.2 mm top distress. size SMA gradation in comparison with a continuous, 3/8-in top size gradation To achieve the stone-on-stone skeleton, representative of HMA practice in the an aggregate blend rich in coarse material United States. is used in SMA. Details of the SMA mix design vary somewhat from country to The weight of the bitumen content of country, and from contractor to contrac- SMA is usually within the range of 6.5 to tor, as will be seen in the following sec- 7.5 percent by weight of the mixture. The
European Asphalt Study Tour 1990 71 filler-to-bitumen ratio of SMA far or fiber content. For example, in Ger- exceeds the upper limit of 1.2 percent many an &solute tolerance of 10 percent recommended in the United States for is allowed in the aggregate gradation (if conventional, continuously-graded the 8 to 11 mm fraction were specified at mixtures. 20 percent, the allowable range would be 18 to 22 percent). For the filler, the Cellulose or mineral fibers are widely tolerance is even stricter, &S percent. employed to stabilize the binder-rich SMA mixtures and prevent their sepa- Liljedahl (l990) gives an excellent ration during production and laydown. discussion of the critical nature of SMA When cellulose fibers are employed as mixtures. Too much mastic will spread the modifier, they are added at a rate of the coarse aggregate apart, leading to a about 0.3 weight percent of the mixture2. pavement that is susceptible to shear. Too Such modifiers as carbon black and poly- little mastic will create an unacceptably mers are allowed as stabilizing additives, high air voids content, expose the bitu- but the EAST members did not observe men to accelerated aging and moisture examples of their use. damage, and lead to a poorly-bound, distress-prone pavement. The SMA is usually designed to have an air voids content of 3 percent. This target In addition to its structural capabilities, value provides an air voids content of less an SMA pavement surface has a granular than 6 percent in in-situ pavements, as texture characterized by large, rough required by European specifications. depressions. This surface offers good skid Field compaction is needed primarily to properties over time. The skid resistance orient the aggregate exposed in the upper of the SMA surface, however, may be part of the pavement; little additional lessened during approximately the first densification occurs under the rollers. month of service until the initial thick Because the mastic is not substantially binder film on the surface wears off under compacted during construction, it must traffic, exposing the rough edges of the be rich in bitumen to obtain the essen- coarse aggregate particles. Bitumen- tially voidless character needed for coated crushed sand (sized between 1 and satisfactory durability. 3 mm) is sometimes rolled into the hot SMA surface at a rate of 600 to 900 grams The stone skeleton must accommodate all per square meter to provide added skid the mastic while maintaining point-to- resistance until the surface film of binder point contact. Therefore, little latitude is is removed. permissible in the production control of the aggregate gradation, bitumen content,
2 Existing specifications usually allow the addition of cellulose fibers at concentrations up to 1.5 percent of the weight of the mixture, but concentrations greater than 0.3 per- cent are rarely used.
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Stone Mastic Asahalt in Germany a top size of 11 mm. However, SMA mixes used for surface course reha- Design--The German specification for bilitation generally employ a smaller SMA is contained on pages 47 and 48 of top size (8 mm). the publication entitled Supplementa Technical Specifcations and Guidelines on A bitumen content of 6.5 to 7.5 per- Asphalt Swjkce Courses. Three SMA cent by weight of the mixture is spec- compositions are provided, differing in ified except for the 5 mm top size the top size of the aggregates (5,8 or 11 aggregate mixture, where 7 to 8 per- mm) and the grade of bitumen employed cent is recommended. All mixtures (penetration grades B65 or B80). Figure 2 require a stabilizing additive, usually compares the aggregate gradation limits cellulose fiber weighing about 0.3 per- for the three SMA compositions. cent of the mixture. FIGURE 2 100 90 80 70 60 50
40 30 20 10 n -0.05 .l 1 10 15 SIEVE SIZE, mm
The recommended thickness of the SMA Because of lower cost, higher possible overlay varies with the top size of the mixing temperatures, and increased time aggregates. When the top size is 11 mm, available for paving, cellulose fibers are the thickness ranges from 25 to 50 mm. A preferred to polymers as a stabilizing thickness of 15 to 30 mm would be suit- additive. Fibers have proven to be a able when the top size is 5 mm. The SMA conservative, secure choice for the SMA overlay thickness is determined by the stabilizing additive because they help class of roadway it is placed on. For the reduce the mix segregation that may Autobahns and other heavy-duty motor- result from small changes in the bitumen ways, the standard appears to be a 40 mm content during production. For example, overlay incorporating the SMA design for 0.3 percent cellulose fibers provides an
European Asphalt Study Tour 1990 73 excellent margin of safety; under u creep compliance, and resilient modulus, conditions, as little as 0.1 percent might do not appear necessary for selection of be adequate. the final SMA job mix formula.
In theory, mix designs in the usual sense Construction--Operationally, SMA are not carried out in Germany for SMA construction in Germany does not or any other type of asphalt-aggregate present any unique difficulties compared mixture. Instead, the mix designs for with construction of conventional asphalt the surface and base courses on a particu- concrete overlays. In fact, some road lar project are selected from a series of authorities consider SMA easier to lay standard designs. These have been devel- and compact than conventional mixes, oped through experience for different especially in thin layers, and less sensitive classes of traffic volume. This approach to poor quality construction practices. requires careful selection of materials, tight control of the variables in the hot- The EAST members witnessed a pave- mix production process and, generally, ment reconstruction project and a main- strict adherence to all requirements of tenance overlay in Germany involving the the specification. use of SMA, and also observed SMA pro- duction at a hot-mix plant. The recon- In practice, since the SMA specifications struction project was on the A-65 Auto- do allow some latitude in the details of bahn near Neustadt an der Weinstrasse the aggregate gradation and the bitumen (appendix A, SVR g-13-90, #2). and additive contents, the voids analysis procedure in the Marshall mix design Substantial rutting had developed in the method is sometimes used to narrow the right-hand (driving) lane of the original specific job mix formula. For example, pavement. No estimate of the average Marshall specimens are prepared at 50 daily traffic (ADT) was given, but all the blows per side for several bitumen con- Autobahns observed carry heavy traffic. tents mixed with a selected aggregate The average ADT for the Autobahn gradation at 135+5’C. The bitumen con- system is 39,000, with trucks comprising tent that yields a Marshall air voids 20 percent of the total; by law, trucks are content of 3 percent is selected as the limited to the driving lane. target value for the job mix formula. The lane had been milled to a depth of 38 Alternatively, road authorities in the cm; reconstruction was in progress, with German state of Lower Saxony recom- conventional asphalt and cement-treated mend beginning with a bitumen content base courses and an asphalt binder course of 6.8 percent and checking to determine replacing the milled-out material. The if the compacted mixture has an accept- EAST team observed asphalt base course able air voids content. In either case, construction. Both lanes of the Autobahn further mechanical or engineering test will be surfaced with a 40 mm SMA over- requirements, such as Marshall stability, lay over an impermeable membrane.
European Asphalt Study Tour 1990 74
The members of the EAST observed compacted SMA surface appeared rich production of SMA for the reconstruction in bitumen. Stone chips were then rolled project at a batch plant in Bitzfeld (SVR on for extra skid resistance. 9-14-90, #4). Operations appeared generally consistent with United States Cost and Serviceability--In Germany, practice except for the addition of the the bid price for an SMA overlay is gen- cellulose fiber as a stabilizing additive erally about 120 percent of that for con- for the SMA. The cellulose fibers, pack- ventional asphalt concrete overlay, term- aged in 1 kg polyethylene pressure-packs, ed asphaltbeton in the ZTV bit-StB 84. were added by hand to the hopper carry- When a polymer is employed in place of ing aggregate to the pug mill. The aggre- cellulose fiber as the stabilizing additive, gate and fibers were dry mixed for 6 to the cost increases to 130 percent of con- 10 seconds, after which the bitumen was ventional asphalt concrete. (Depending introduced. The normal mixing time was on the mix design, the cost of hot mix at increased by a few seconds to ensure sat- the plant is $40 to $70 per ton in isfactory blending of the materials. (The Germany; see SVR 9-12-90, #l). polyethylene film used for the fiber pack- ages has a very low melting point and A substantial service life is expected for rapidly dissolves in the hot ingredients). this increased cost. On normally-traffic- ked Autobahns and heavily-trafficked The maintenance project on Route 19 federal highways (corresponding respec- near Schwbisch Hall (SVR 9-14-90, #5) tively to the United States Interstate and involved placement of a 25 mm SMA primary systems), SMA overlays are the overlay on a heater-planed pavement surface course of choice. A normal ser- surface. The SMA mix had a nominal vice life of 10 to 15 years is expected. By aggregate top size of 8 mm. Again, an contrast, asphaltbeton surface courses are estimate of the ADT was not given. recommended for normally-trafficked Route 19 is a rural route; on average, federal highways and lesser-trafficked roads of this class in Germany have an local and regional road networks. A ADT of about 3,000. service life of 8 to 12 years is expected. All other things being equal, SMA is The existing pavement surface, which expected to yield up to 25 percent longer showed only random, minor distress, was service than a conventional overlay. recycled with a heater-planer unit. The SMA overlay was immediately placed In-Service Pavements--A good example with a conventional paver and compacted of the use of an SMA surface course is by two static, steel-wheeled rollers run- described in SVR 9-12-90, #2. It des- ning in tandem. (Vibratory compaction is cribes a 6-year old SMA surface course not recommended, at least after the first the EAST team observed on the Barm- rolling pass, since it has been shown to bekerstrasse in Hamburg. This urban draw bitumen to the pavement surface; street has an ADT of 40,000, including rubber-tired rollers are also not recom- 6 percent truck traffic. The entire pave- mended). The SMA occasionally showed ment structure is 740 mm or about some marking under the rollers. The 29 inches thick and is built upon
European Asphalt Study Tour 1990 7s
frost-proof sand. The pavement did not In Sweden, SMA was introduced in the show any signs of distress. Hamburg road late 1960’s to reduce pavement damage authority personnel indicated the typical caused by studded tire use. Asbestos service life for SMA in similar fibers were employed as the stabilizing circumstances is 10 years. additive (as also was the case in Germany at that time). Shortly, however, asbestos The EAST team also rode over an exten- was prohibited because of health, safety, sive SMA surface on the A-7 Autobahn and environmental concerns. A corres- about 12 km north of Kassel in the state ponding hiatus in the use of SMA occur- of Hessen. This pavement was about red until cellulose fibers were introduced 2 years old; no distress of any significance in the early 1980’s. was visible at Autobahn speeds of 55 to 60 miles per hour. The ride was smooth. The principal function of HABS overlays in Sweden continues to be the reduction Stone Mastic Amhalt in Sweden of studded tire damage. Swedish SMA design differs from the German design in Design--The Swedish National Road several ways. First, nominal aggregate top Administration’s (SNRA) term for SMA sizes in Sweden are larger. Swedish grad- is HA&S; the Swedish term for conven- ations for SMA are based on top sizes of tional, continuously-graded asphalt con- 12 mm (HABS 12) and 16 mm (HABS crete is HAM’. The Swedish national 16) compared with the German top sizes specifications for SMA are contained in of 5,8 and 11 mm. (Swedish authorities SNRA (Vgverket) publication are considering SMA designs based on a 1988:42,. e Fr&& 22 mm top size). The gradation limits for We- (Slitlager av HABS), the HABS 12 and 16 are shown in figures December 1988. 3 and 4. Laboratory studies by the SNRA
FIGURE 3
90 80 70 60 50 40 30 20 lo
1 SIEVE SIZE, mm European Asphalt Study Tour 1990 76
FIGURE 4
90 othBS16 80 70
1 SIEVE SIZE, mm indicate that HABS 16 will yield as much fibers are less common. The SMA as a 40-percent reduction in studded tire specification also permits the use of wear compared with HABS 12. powdered rubber and polymers.3
Second, the variety of stabilizing additives Third, and last, SMA is marketed by at employed in Sweden is greater. Cellulose least two major Swedish paving contrac- fibers are employed in loose form and in tors under proprietary trade names: preformed pellets composed of equal Stabinor available from Skanska Entre- parts by weight of fibers and bitumen. prenad AB and Vkzcotop from NCC Bygg The latter form is easier to handle in AB (Nordic Construction Company). hot-mix production operations and less Both products conform to the SNRA dusty than the loose fibers. It would be specification, but differ in several ways essential for SMA production in drum that will be discussed in the following mixers. In addition, mineral fibers are sections. widely used, while fiberglass and plastic
3 Field experiments are underway on the E-3 motorway in Goteborg to compare the performance of an SMA overlay containing Styrene-Butadiene-Styrene (SBS)-modi- fied bitumen with an overlay using a conventional B85 bitumen. Apparently, cellulose fibers are used with both binders. After two winters, the two overlays exhibited little apparent difference. The monitoring will continue for several more years.
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In Sweden, recommended SMA overlay achieve a job mix formula with a Marshall thicknesses range from 34 to 43 mm for air voids content of 3 percent. The speci- HABS 12, and 38 to 47 mm for HABS 16. fication does not provide any require- The SMA overlays are advised for all ments for Marshall properties other than Swedish roads with an ADT over 15,000 the air voids content. or where studded tire damage is the main cause of distress. In practice, this usually Many Swedish contractor personnel means all roads with an ADT of 4,000 or stressed the importance of the 2 mm sieve more, and particularly those in the south- size in judging the acceptability of the ern part of the country where the traffic SMA design and in the field control of density is highest. the hot-mix production. While the specifi- cation permits the amount of aggregate The Swedish specification advises a target passing 2 mm to vary between 16 and bitumen content of 6.3 percent for HABS 29 percent for HABS 16 mixes or 19 and 16 and 6.6 percent for HABS 12; in both 30 percent for HABS 12 mixes (similar to cases, a bitumen of grade B 85 (85 pene- the German specification), the contractor tration grade is recommended). The use personnel strongly advocated a more of a stabilizing additive is ti required, stringent requirement of no more than 20 but the contractor is given wide latitude to 23 percent passing the 2 mm sieve. to employ additives if they are judged to be warranted. The specification notes that Liljedahl (l990) demonstrates that allow- when additives are used, the bitumen ing more than 23 percent of the aggregate content may require adjustment above to pass the 2 mm sieve (or, conversely, the suggested levels. employing an aggregate gradation with less than 77 percent coarse aggregate) In addition to gradation requirements, increases the mastic volume to a point the coarse aggregate must satisfy specific where the necessary stone-on-stone con- test limits for abrasion resistance, flaki- tact of the coarse aggregate and, conse- ness index, impact crush strength, and quently, the rutting resistance of the SMA proportion of crushed material. are lost. Additionally, he shows that the absolute necessity for stone-on-stone The voids analysis procedure of the contact in the SMA mix also requires that Marshall mix design method is employed the largest stones make up the bulk of the to develop the job mix formula for SMA coarse aggregate. For example, for an mixes. In practice, an initial target value HABS 16 mix, at least 70 percent of the for the bitumen content is obtained by aggregate should be in the 10 to 16 mm measuring the void space in the coarse sizes. aggregate (retained on the 2 mm sieve). With this quantity, the allowable volumes Construction--The EAST team witnessed of the mastic and the air voids in the com- the construction of two SMA overlays in pacted mix can be calculated for a range Sweden. They also visited a hot-mix plant of bitumen contents. Then, the bitumen near Goteborg that routinely produces content and the aggregate gradation are SMA mix. adjusted within the specified limits to
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Both SMA overlay projects were on mately 5/8-inch) top size. The gradation European Route E-6, a divided four-lane, falls outside the limits presented in limited-access motorway that runs north- Slitlager av HABS for HABS 16 at the south along the west coast of Sweden. 8 mm sieve size and above. Based on The two projects were approximately Liljedahl’s analysis (1990), this might be 55 miles apart on the portion of the E-6 considered a “critical” mix since the void between Goteborg and Halmstad to the space in the coarse aggregate could be south. The ADT is about 13,000, with insufficient to accommodate the mastic truck traffic comprising about 25 percent and achieve stone-on-stone contact. of the total; in the winter months 65 to 75 percent of the vehicles use studded The original pavement at this location tires. Compacted overlay thickness was did not show substantial distress; how- specified at 38 mm for a general HABS ever, photographs taken at the time of 16 mix design. the visit show some studded tire wear in the wheel paths. The SMA was placed The northerly project (SVR g-10-90, #5), over a thin (12 to 16 mm) leveling course near Varberg, was under construction by with a conventional Dynapac paver at Skanska Entreprenad AB using its a temperature of 16O’C. Two steel- Stabinor SMA mixture. Inorphil mineral wheeled rollers followed close behind fibers were employed as the stabilizing the paver; vibration was not used. The additive, introduced at a rate of 8 percent contractor personnel indicated that by weight of the binder (0.5 percent by rolling is mainly intended to orient the weight of the mixture). An 85-penetra- stone skeleton in the overlay rather than tion grade bitumen (B85) was employed. to compact the mat substantially. Rolling Twenty percent of the stone (coarse is permitted until the mat temperature aggregate) was described as “qualified’; falls to 75’C; the second roller in the that is, it meets the minimum require- train was equipped with an infrared ments established in Slitlager av HABS pyrometer for this purpose. for SMA coarse aggregate.4 The southerly project (SVR g-10-90, #7) The Stabinor gradation used in this proj- was near Bastad. As with the northerly ect is shown in figure 5, where it is com- pavement near Varberg, the existing pared with that of Viacotop as well as the pavement surface on the southerly project recommended gradation limits for a con- did not exhibit exceptional distress. The ventional United States dense-graded project was under construction by NCC asphalt concrete with a 16 mm (approxi- Bygg AB using its trade named VYacotop
4 This implies that the quality requirement was waived by the road authority for the remainder of the stone. In Sweden, “qualified” stone intended for use in HABS overlays is generally quartzite or porphyry that must often be obtained from remote sources. For this project, the cost of the qualified stone is estimated at 46 Swedish kronor per square meter or about $0.75/square foot of roadway.
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FIGURE 5
innIUU
90 80 70 60 50 40 30 20 10 n 1 10 20 SIEVE SIZE, mm SMA mixture. Cellulose-bitumen pellets the Stabinor mix. The amount passing the were used as the stabilizing additive. They 2 mm sieve, the dividing line between the were added at a rate of 0.6 percent by coarse aggregate and the sand and filler weight of the mix, yielding a cellulose fraction, is only 22 percent, compared fiber content of 0.3 percent. The bitumen with 25 percent for the Stabinor (as noted (grade B85) content of the Viacotop earlier, many Swedish authorities prefer HABS 16 was 6.7 percent by weight of the the lower figure at this sieve size). These mix. This was considerably higher than differences in gradation allow the Viaco- that used in Skanska Entreprenad AB’s top mix to accommodate the increased Varberg project, even considering that bitumen content; in theory, this leads to 0.3 percent is contributed by the cellulose lower compactive effort and increased pellets. durability of the SMA.
The aggregate gradation (figure 5) in this The SMA was laid with a conventional Viacotop mix conforms more closely than paver and rolling was accomplished by the Stabinor mix with the gradation limits two 10-ton rollers. Roller marks were presented in Slitlager av HABS for a typi- much less pronounced than for the cal HABS 16 mix. In particular, 60 perent Stabinor mix. The compacted pavement of the aggregate is retained on the 12 mm surface appeared rich in binder, almost sieve, compared with only 30 percent for to the point of flushing, but the road auth-
European Asphalt Study Tour 1990 80 ority and contractor personnel reported overlays on motorways, primary routes, that Viacotop has good friction properties industrial streets, congested urban inter- when newly laid. Unlike the German sections and bridges with an ADT greater practice, no stone chips or sand were than about 5,000. NCC Bygg AB alone rolled on either project to provide extra placed almost 300,000 tons in 1990 or initial friction. about 32 million square feet of overlay.
The batch plant in suburban Goteborg Personnel of the Goteborg city road produces SMA as well as conventional authority indicated to the EAST team HMA and porous asphalt mixes (SVR that SMA has become the overlay of g-10-90, #4). No production was under- choice in recent years for most of their way at the time of the visit. Unlike the road surfaces because of its enhanced German hot-mix plant described in the resistance to rutting caused by increased previous section, this plant has a mechan- traffic volumes and the action of stud- ical system for dispersing both cellulose ded tires. In Goteborg, traffic volumes and mineral fibers into the pug mill. increased dramatically year-by-year in the 1980’s and typically 70 percent of the This plant (of several in Sweden) is also vehicles in the city use studded tires capable of handling the cellulose pellets during the winter. Yet in the Tingstad mechanically. The pellets are delivered tunnel, which EAST visited to see an in 700 kg sacks (1,543 pound). These are in-service installation, city road authority hoisted into a storage silo where an inter- personnel indicated that SMA overlays nal knife cuts them open, depositing the have experienced only 17 mm of rutting pellets in the silo. The pellets fall by gra- after 30 million vehicle passes compared vity through a pipe to the same scale used with 25 to 30 mm for the previous HABT to weigh filler. The weighed pellets are surface after 25 million vehicle passes. conveyed by a screw drive into the pug mill. In-Service Pavements--The EAST team observed a variety of in-service SMA Cost and Serviceability--In Sweden, SMA pavements around Goteborg and on the hot mix (HABS) costs about 10 percent E-6 motorway between Goteborg and more than continuously-graded, dense Helsingborg. hot mix (HABT in SNRA terminology) employed for overlays. The precise In the eastbound lanes of the Tingstad differential depends on the material used tunnel in Goteborg (SVR g-10-90, #l), as the stabilizing additive. a Stabinor (HABS 12) SMA overlay con- structed in 1985 was viewed at normal A 20-percent increase in service life traffic speeds. The ADT is 100,000 over (measured in ADT of vehicles with stud- the six lanes of the tunnel. In addition to ded tires) is a realistic expectation for a mean rut depth of 17 mm, the pavement SMA compared with dense-graded HMA exhibited some rutting due to studded overlays. The favorable Swedish exper- tires, but not uniformly through the ience has led to the use of SMA for most length of the tunnel. Other types of distress were not visible. A 20-percent
European Asphalt Study Tour 1990 81 increase in service life is projected for the Further south on the E-6, an SMA over- SMA overlay compared with the con- lay (HABS 12) constructed in 1987 was ventional HABT used previously. examined. No rutting or cracking was noted, but some aggregate pop-outs were A S-year old VTacotop (MS 12) SMA apparent in the driving lane. The SNRA overlay was observed on a four-lane personnel with the EAST indicated that a urban street in the Stlhandskegatan 10- to 12-year service life was forecast, district of Goteborg (SVR g-10-90, #2). based on the little distress measured to Measured rut depth was 10 mm with a date. 30,000 ADT over four lanes. Little or no distress of any kind was noted at normal Stone Mastic AsDhalt in Denmark traffic speeds. This overlay had been constructed by the forces of the Goteborg The use of SMA is not as widespread in Street and Highway Department. Denmark as it is in Germany and Sweden. The Danish Road Directorate indicated A l-year old SMA pavement on the E-6 that a gap-graded asphalt concrete mix south of Varberg was inspected by the design, similar to the hot-rolled asphalt EAST team on foot (SVR g-10-90, #6). described in a later section on the United This overlay used an 18 mm top size Kingdom, is used extensively to prepare aggregate; only local, unqualified stone rut-resistant surfaces on roadways was used. The pavement surface was wet subjected to heavy truck traffic. from an earlier rain shower, and showed an irregular drying pattern that empha- However, the EAST team did see some sized what appeared at first to be ravel- interesting examples of in-service SMA ling in areas away from the wheel paths. pavements in Denmark. The most note- The United States contractors in the worthy is the modified SMA overlay EAST, however, agreed that the inspected on the Helsingor (E-4) Motor- condition more likely arose from mix way (40,000 ADT, 5 percent trucks) that segregation during construction than loss runs north from Copenhagen (SVR of aggregate during service. The wheel g-11-90, #2). The SMA was the 40 mm paths appeared normal, perhaps wearing course of a 100 to 200 mm reflecting movement of the mastic to the asphalt concrete overlay placed between surface under traffic. No other distress 1988 and 1990 on the original 30-year old, was noted. distressed PCC pavement. The PCC had been either cracked and seated or com- On the E-6 motorway south of Goteborg, pletely removed, depending on its state of the SMA surface (HABS 16, built in deterioration. 1988) had a smooth, almost flushed appearance. Aggregate was less apparent The contractor, Superfos Dammann- on the surface than on the section Luxol a/s, selected an SMA wearing described previously. No distress of any course because of its good durability and consequence was noted on the pavement resistance to deformation. A bitumen surface. modified with both an SBS-type polymer and cellulose fibers was chosen as the
European Asphalt Study Tour 1990 82 binder to obtain a highly flexible, crack traffic. By contrast, the passing lane had resistant pavement surface. The modi- an even appearance. The only distress fied bitumen content was 6.9 percent by noted was slight rutting in the wheel weight of the mix; SBS polymer com- paths of the driving lane. prised 6 percent of the binder. Cellulose fibers, which comprised 0.25 percent of The EAST members also examined an the mix, cost $0.65 per pound or about SMA surface course on the E-4 motor- $3.25 per ton of hot mix. The aggregate way on the way south from Copenhagen gradation generally falls within the to Rodby, just north of the Route 37 SNRA’s limits for HABS 12 mixes. interchange. This surface course was 2 years old and had flushed in the wheel The driving lane presented a slightly paths of the driving lane. The Danish flushed appearance in the wheel paths, road authority personnel indicated but as noted for the E-6 motorway in that the flushing had reduced the skid Sweden (SVR 9-10-90, #6), perhaps this resistance appreciably. It is suspected appearance signaled movement of the that the binder content of the SMA mix mastic to the surface under the action of was too high. POROUS ASPHALT
General Descriwtion hydroplaning is not a significant concern. In addition, the French road authorities In general, PA may be considered the note that the open texture of the PA European equivalent of the open-graded helps reduce reflected glare from asphalt friction courses (OGAFC) or headlights. open friction courses (OFC) used in the United States. Both are intended to The EAST members observed PA provide a wearing course that rapidly wearing courses in France, Germany, drains rainwater from the pavement and Sweden. France and Sweden have surface and reduces hydroplaning. For standard specifications for PA mixes comparison, the original United States (discussed later) and use PA routinely. design method for OGAFC is given in In Germany, PA appears to be treated Smith et al. (1974). as an experimental feature, intended mainly as a noise reducer, but is in In Europe, PA is also used to reduce increasingly greater demand as public traffic noise where high-capacity road- concern about traffic noise grows. (In ways are in populated areas. In contrast the United Kingdom,porous macadam with the United States, many European surfacing has been examined, but has not mix designs for wearing courses have a yet been adopted by specifying agencies; harsh macrotexture that generates sub- consistently demonstrating a favorable stantial tire noise. Porous asphalt pro- cost-to-benefit ratio for its use has not vides a way of absorbing and dissipating been possible). this noise within the pavement surface and is favored for use even where
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The main characteristic of PA mixes is authorities appears to have an effective their high air void contents, in the range maintenance procedure to reverse this of 20 percent or more, which provide the trend so the useful service life of the PA “open” nature necessary for water drain- is limited by how fast the air voids fill with age and noise muffling. These air void debris. Another facet of this problem is content values are obtained by using gap- that the open structure of PA pavements graded aggregates or by reducing the pro- requires increased amounts of deicing portion of fine aggregate and filler in the chemicals and abrasive for effective snow total continuous aggregate gradation to and ice control, and the pavements are less than 20 percent of the weight; and, in more difficult to keep free of frost and ice. either case, by employing binder contents in the range of 5 percent of the total In the United States, the use of OGAFC mixture’s weight. has been hampered by unfavorable exper- ience with the stripping and deteriora- Modified bitumens appear to be used tion of underlying pavement courses. To exclusively in PA mixes. The EAST team address this problem, European practice saw examples of binders modified with requires placement of an impermeable cellulose and mineral fibers, polymers membrane or seal layer directly under PA such as SBS latex, and even reclaimed tire surface courses to prevent the intrusion of rubber. As with SMA, the PA binder is water into the underlying pavement modified to prevent its drainage during structure. mix production and transport, but the modification is also intended to increase Porous Asphalt in Sweden the durability of the mix when it is exposed in situ to air and water. Design, Cost and Serviceability--The SNRA's term for PA is HABD, which is To be effective, PA surface courses must roughly translated as drainage asphalt be linked with pavement drain systems. concrete. The Swedish national specifi- Germany and Sweden have construction cations for PA are contained in SNRA requirements on the smoothness of the (Vagverket) publication BYA 84, Techni- base or binder course under the PA cal Specifications for Construction and surface as well as minimum transverse General Advice (Byggnadstekniska crossfall in the pavement to promote foreskrifter och allmannna rad) , 1384 drainage through the PA surface to the edition, pages 30 through 35. The drains. specifications for HABD 12 and HABD 16 mixes are based on top aggregate sizes of 12 and 16 mm, respectively. All PA pavements experience a gradual decrease in drainage and noise reduction as they become filled over time with air- Figure 6 (found on the following page) and water-borne debris, anti-icing abra- compares the aggregate limits established sive, etc. This is particularly a problem in for HABD 16 with those for the SMA mix urban areas where low traffic speeds are HABS 16. The two gradations overlap not effective in flushing debris forcibly substantially above the 4 mm aggregate through the PA layer. None of the road size, but the proportion of fine aggregate
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FIGURE 6 100 o HAl3Sl6 90 n HABD 16 80 70 60 50 40 30 20 10 n -0.05 .l 1 10 25 SIEVE SIZE, mm and filler in the HABD 16 mix is substan- aggregate quality requirements for tially lower than that in the HABS 16 mix. HABD mixes are similar to those Since the coarse aggregate (retained on discussed above for HABS mixes. the 2 mm sieve) gradation is similar for the two, the PA mix is expected to have The use of modifiers is not specifically the same stone-on-stone skeleton and required by BYA 84 to prevent drainage resultant performance characteristics as of the binder from the PA mix during the SMA. mix production and transport. However, if stabilizing additives are not used, the A target bitumen content of 5.2 percent PA mix must be maintained at 120 to by weight of the mix is specified for both 135’C during construction to deter HABD 12 and 16, compared with 6.6 per- binder drainage. The specification does cent for Swedish SMA mixes. The SNRA require the use of amine-type anti-strip notes, however, that even 5.2 percent is agents to alleviate the damaging effects of a high binder content in relation to the moisture in the open structure of the PA aggregate grading curve. Thus, HABD mixes have adequate resistance to chang- The thickness of the PA surface layer es in the binder caused by exposure to air, also is not specified. The PA course water, deicing chemicals, etc., but their must be placed on an impermeable bitu- overall durability is not expected to be as minous tack coat or membrane to pre- good as that of SMA. Bitumen grade and vent moisture damage to the underlying pavement.
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The SNRA indicated that the cost of PA In-Service Pavements--The EAST mem- is similar to that of SMA, but that the bers observed in-service PA pavements in durability of the PA is no better than that the Goteborg area and on the E-6 motor- of conventional HMA. Indeed, in many way between Goteborg and Helsingborg. cases, PA is much less resistant to stud- ded tire damage than conventional. . . HMA. On the westbound lanes of Brackevagen the use of PA must be justified on a . (Route 159) in Goteborg (SVR g-10-90, asls where the benefits . of #3), a 43 mm-thick Drainor (HABD 16) mse redwiuuuuandr dra1na.e PA overlay constructed in 1986 was view- outwelPh the increased cost . ed at normal traffic speeds. Drainor is the trade name for PA produced by the Measurements on PA pavements in Skanska Entreprenad AB. Goteborg in the early 1980’s indicated that the initial 4.8 dB(A) noise reduction This PA mix contained 5.0 percent binder fell to 0 dB(A) within 2 years of service. by weight of the mix; the binder was mod- Similarly, the water drainage capacity of ified with Inorphil mineral fibers at a rate the pavements was found to decrease by of 0.8 percent by weight of the binder to 50 percent within 3 years. These prevent binder drainage during construc- decreases in serviceability were blamed tion.5 Of the coarse aggregate, 55 percent on silting of the void spaces with debris was quartzite, a very hard mineral aggre- and studded tire damage. The Goteborg gate that does not crush during compac- road authority considers these levels of tion and resists studded tire wear. The air performance sufficient to justify PA use voids content of the compacted mix at the in certain instances. time of construction was greater than 15 percent. Obviously, PA surfaces cannot be reha- bilitated simply by overlaying. The old Personnel of the city road authority PA layer must be milled off, and the indicated that the measured mean rut pavement must be recycled or sealed depth was between 6 and 7 mm; ADT is with bitumen. The SNRA does not allow, 25,000 over the four lanes of the highway. under any circumstances, the encapsula- The pavement was viewed at speed from tion of an old HABD layer between the bus; little or no significant distress other types of bituminous courses. was visible. The pavement surface, how- ever, appeared rough, with aggregate showing.
5 Limited field experiments in Goteborg with PA mixes containing a binder modified with both mineral fibers and 6 percent styrene-butadiene thermoplastic suggest that polymer modification increases the durability of the binder against wear and weathering.
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In Goteborg, only HABD 16 mixes are and to prevent hydroplaning by draining used; the HABD 12 mixes were found to rainwater. Experimental pavements have have poor resistance to studded tire dam- already yielded 6 to 7 years of satisfactory age, lasting only about half as long as con- performance. ventional HMA surface courses. The city road authority selects the use of new PA Larmmindernde Asphalt mix designs are surface courses primarily to reduce traffic available with both 8 and 11 mm nominal noise; in the city, water drainage is of aggregate top sizes. Mixes are designed secondary importance. to have an air voids content in excess of 20 percent. In practice, compacted The EAST study team also drove over a Larmmindernde Asphalt pavements have PA surface course at the entrance to the air voids contents ranging from 15 to Tingstad tunnel in Goteborg (see SVR 25 percent. This percentage is achieved 9-10-90). This surface course was placed by using a very high proportion of coarse in 1984 and has distinct ruts caused by aggregate (retained on the 2 mm sieve), studded tire wear. The city road authority a low sand and mineral filler content, and personnel indicated that the rut depth a binder content of about 5 percent by was about 25 mm. weight of the mix.
In addition, several sections of PA sur- The existing pavement is milled out, one facing on the E-6 motorway between lane at a time, to a depth of 70 mm. A Goteborg and Helsingborg were exam- new 70 mm-thick asphalt binder course is ined. One section of unknown age was placed, followed by an impermeable seal contiguous to an SMA surface course. coat. The seal coat is prepared by apply- After a moderate rainfall, much less ing a polymer-modified cationic bitumen water was visible on the PA than on the emulsion at a rate of 2 kg/m2 and dressing SMA surface. Another PA section it with chippings applied at 8 to 10 kg/m2. (15,000 ADT) had been built in 1982 and recycled in 1988. The recycled mix had a A 40 mm-thick Larmmindernde Asphalt compacted air voids content of 12 per- surface layer is then applied. This em- cent, compared with 15 percent in the ploys an 11 mm top size coarse aggregate; original mix. No substantial degree of 85 percent of the aggregate is retained distress was noted. on the 2 mm sieve. The mineral filler passing the 0.09 mm sieve represents a Porous Asuhalt in Germanv nominal 5 percent of the total aggregate. The binder is a polymer-modified cat- Germany does not yet have standard ionic B65 bitumen emulsion containing specifications for PA (termed 0.5 percent (by weight of the mix) Larmmindemde Asphalt) in Germany. cellulose fibers. The German road authorities consider it an experimental feature, but are under German practice uses polymer-modified increasingly strong public pressure to use bitumens exclusively in Larmmindernde it to reduce traffic noise. As in Sweden, Asphalt; this is done to increase binder- PA is employed to reduce traffic noise
European Asphalt Study Tour 1990 87 aggregate adhesion in the presence of (SVR g-14-90, #3). The pavement copious amounts of air and water. Cell- section that had been completed in 1990 ulose fibers are also added to the rnix to showed no apparent distress. The ride on reduce binder drainage during construc- the Larmmindernde Asphalt pavement tion. Larmmindernde Asphalt surface was quiet, indicating its effectiveness, at courses are always placed over some kind least when new, at absorbing tire noise. of impervious membrane or seal layer to protect the underlying pavement from Several sections of Larmmindernde water. Asphalt surface course were also viewed by the EAST members on the A-6 Auto- In Germany, the in-place cost of Larm- bahn east of Heilbronn (SVR g-14-90, mindernde Asphalt is about 100 percent #l). The dates of construction are not more than a comparable HMA surface known, but the team did not observe any course. Given the cost, it is primarily used visible distress and the ride was quiet. to reduce noise on highways with high The Larmmindernde Asphalt mix designs velocity traffic, usually in or near residen- used here were virtually the same as that tial areas. As in Sweden, filling of the void employed in the A-81 construction dis- structure in the Larmmindernde Asphalt cussed earlier; however, both 8 and with debris gradually reduces its effec- 11 mm top size aggregate gradations tiveness, and two to three times the were employed. amount of deicing chemicals is needed for snow and ice control. Porous Asuhalt in France
The EAST team saw several examples of Design, Application, and Cost--For pave- this type of mix on the Autobahn system ment surface maintenance, PA is one of (SVR g-14-90, #‘s 1,2, and 3). On the several alternative strategies specified by A-S 1 Autobahn near Freiberg in Breis- the French Transport Ministry (Mnistere gau, reconstruction was underway, includ- de L’Equipement et du Logement des ing placement of a PA surface course on Transports et de la Mer) and its compon- the entire pavement, shoulders, and all ent agencies, particularly the Directorate bridge decks. This is a very high capacity, of Roads (Direction des Routes), the four-lane freeway that had experienced Central Laboratory of Bridges and Roads substantial rutting; the current ADT is (Laboratoire Central des Ponts et 90,000, with trucks totalling 33 percent of Chawsees or LCPC), and the Roads and the traffic. It is noteworthy that Larmmin- Highways Engineering Department dernde Asphalt is considered a viable (Service D’Etudes Techniques des remedy for pavements where load- Routes et Autoroutes or SETRA). induced rutting has been a problem. Porous asphalt is classified with the var- On another project, only binder course ious maintenance techniques that provide construction was underway on the day of no structural effect; this classification the visit (SVR g-14-90, #2) and the places it in the same category as very thin EAST members also observed a pave- asphalt concrete (to be discussed in the ment section completed earlier in 1990 next chapter) and conventional chip seals.
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It is employed to rehabilitate pavement team did not receive information on the surfaces while providing significant noise cost of these PA mixes in-place compared reduction and reduced hydroplaning. with conventional HMA overlays. In France, however, polymer-modified On the French toll motorway system, PA bitumens cost about 100 percent more comprises about 16 percent (22.4 million than unmodified bitumen, and polyrner- ft2) of the surface courses. It is also used modified HMA, as produced, about extensively on the national road system, 20 percent more than conventional HMA. comparable to the United States primary ‘system. The toll motorways have ADT’s In-Service Pavements--Members of the between 7,000 and 50,000, with 15 to EAST inspected three in-service PA 20 percent trucks and maximum single pavements around Nantes and Lyon. axle loads of 13 metric tons. A 25 mm-thick PA overlay on low-traffic General French requirements for PA volume, two-lane RN 23 in suburban mixes differ from Swedish and German Nantes was constructed in July 1989 requirements in two important ways: 1) a (SVR 9-17-90, #2). The PA mix used was gap-graded aggregate blend is employed PERMFLEX, a proprietary product of the with little or no aggregate sized between French paving contractor COLAS S.A. It 2 and 6 mm; and 2) the mineral filler con- employs the modified binder COLFLEX tent (passing the 0.09 mm sieve) is very 253, an SBS6 latex-modified bitumen. The small, usually 1 to 1.5 percent of the total binder content of the mix is 5.2 percent; aggregate. the SBS latex comprised 5 percent by weight of the binder. Aggregate top size Nominal aggregate top sizes of 10 and was 10 mm. Nominal air voids content 14 mm are used; the coarse fraction was 23 percent. (2 mm) typically makes up 85 percent of the total aggregate. Air voids contents are The underlying pavement was prepared designed at about 22 percent. Binder by application of a tack coat of polymer- compositions over a wide range are modified bitumen emulsion. The PA allowed, including pure bitumen, poly- overlay was placed with a conventional mer-modified bitumen, rubber bitumen, paver and compacted with steel-wheeled and fiber-modified bitumen. rollers. The overlay was placed thinner than usual to prevent frost build-up on Major French paving contractors produce the pavement during the winter months. proprietary or trade named PA mixes to The pavement had an open appearance, satisfy the general French PA specifica- but no distress was apparent. tion. These mixes feature modified bitu- mens to provide perceived benefits in performance and durability. The EAST
6 SBS = styrene-butadiene-styrene block copolymer.
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Another PERMFLEX overlay was 5 percent by weight of the binder. The inspected on Boulevard Dolon in Nantes gap-graded aggregate has a top size of (SVR g-17-90, #3). This was also con- 10 mm; 88 percent falls between 6 and structed in July 1989. In this case, a two- 10 mm. A hard, crushed porphyry rock is layer pervious pavement was used: a used for the coarse aggregate. 20-mm PA overlay basically identical to that employed on RN 23 over a 60 mm This type of overlay is also placed with pervious bituminous macadam base conventional pavers and compaction course. This two-layer construction was equipment. The hot mix plant, however, used to provide the pavement with the must be equipped with a special unit for capacity to store large volumes of precise production of the rubber-bitumen rainwater temporarily. binder.
The pervious base course, which uses an Inspection of this DRAINOCHAPE FE unmodified 60/70 penetration grade bitu- pavement showed it to be in excellent men, has an aggregate top size of 14 mm condition after 1 year of service. The and a binder content of 4.8 percent. A pavement surface appeared fresh, with- gap-graded aggregate was used, rich in 10 out any visible distress. to 14 mm sizes, but with little mineral filler content. This heavily-trafficked The EAST members were also shown urban route did not show any apparent a 2-year old PA overlay on a steeply- distress after 1 year in service. sloped suburban street in the Lyon area. The overlay, which is approximately The A47 toll motorway south of Givois 45 mm thick, was produced with a poly- in suburban Lyon is a heavily-trafficked mer-modified bitumen and a gap-graded route to the French Riviera. In the sum- aggregate blend with a nominal 14 mm mer, the traffic volume is on the order top size. The air voids content was 20 per- of 160,000 ADT. The EAST members cent. During the summer of 1990, the air inspected a 40 mm-thick PA overlay temperature had reached 40°C daily for constructed in July 1989 (SVR g-18-90, several weeks and the pavement temp- #l). The PA mix used was DRAINO- erature 60°C. Remarkably, little or no CHAPE FE, a proprietary product of the visible distress was noted in the overlay. French contracting firm BEUGNET Technical Management. It employs a proprietary bitumen-rubber binder, FLEXOCHAPE E, also produced by BEUGNET. Reclaimed tire rubber treated with aromatic oil is used. The binder content of the PA mix is 6.6 per- cent. The reclaimed rubber content is
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MODIFIED ASPHALTS AND ASPHALT-AGGREGATE MIXTURES
Qneral Remarb modified materials do not exact the same penalties in Europe as they would in the The use of modified binders and United States. bitumen-aggregate mixtures appears much more prevalent and routinely Last, the European paving contractors accepted in the European countries appear to take the main responsibility for visited than in the United States. the development and adoption of Although latex-modified asphalt cement modified materials, and have a direct and asphalt-rubber binder are used in economic stake in their successful use. substantial quantities in several American The promotion of new products by third states, European practice seems to parties, as is prevalent in the United encompass larger volumes of material as States, seems much less common in well as a wide range of modifiers. Europe.
The group’s impression was that the freer stone Mastic AsDhalt and Porous Asphalt use of modified materials arises from several factors. First, the latitude given to The extensive use of a wide range of paving contractors to design and produce bitumen modifiers in SMA and PA mixes pavements that meet specified warranty has been discussed in detail in sections II conditions, rather than the lowest first and III. The production of both types of cost, encourages more experimentation mixes would appear to be difficult with- by the contractors in the use of novel out modifiers. Moreover, the generally materials and mix designs. successful performance of the small sample of SMA and PA pavements Second, major differences in contracting observed by the EAST team suggests the practices permit much higher HMA additional cost and production time prices in Europe than in the United needed for the modified mixes are States. As a result, the additional cost of justified. modified materials is not as significant a factor in choosing the “best” system for Verv Thin Asphalt Concrete (France1 the job at hand. Very thin asphalt concrete (VTAC) is another of the alternative strategies Third, European HMA production, specified for pavement surface mainten- almost exclusively by batch plants, is ance by the French Transport Ministry. geared to relatively smaller daily volumes than in the United States. The additional plant units and production times for
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In addition to providing enhanced skid was placed in 1988 using the MEDIFLEX properties, VTAC is intended to seal and proprietary mix produced by SCREG renew existing pavement surfaces. It is Routes Group. Like COLRUG, MEDI- considered a paver-laid alternative to FLEXuses a binder modified with 5-per- slurry seals, and does not affect the cent SBS latex. This overlay also appear- pavement structurally. ed in excellent condition; close examina- tion did not reveal any overt distress. A VTAC overlay consists of a gap-graded aggregate combined in most cases with a Paver-Laid Chir, Seal @rancel modified bitumen binder. The aggregate top size is 10 mm; 83 percent of the Paver-laid chip seal is another mainten- aggregate is in the 6 to 10 mm range, with ance strategy permitted under French 15 percent between 0.09 and 2 mm. The Ministry of Transport specifications. This remainder of the mixture is limestone technique is not intended to provide any filler. structural effect, and its use is confined to pavements that are not deformed. A variety of modifiers are used, including polymers, rubber, and fibers. Depending The chip seal is constructed with a binder on the modifier selected, the binder con- layer of polymer-modified bitumen emul- tent can vary from 5.7 to 6.7 percent by sion. Hot precoated chips (6 to 10 mm) weight of the mix. The air voids content with a 17 to 1 blend of sand and bitumen of VTAC is high, generally in the range of are applied. A single, self-propelled unit 15 percent. sprays the binder layer and immediately applies the chips. The chip seal is then The East members inspected two exam- smoothed by a rubber-tired roller. ples of VTAC treatments. The first was on route RD 68 between Ste-Lute and Three benefits are claimed for this paver- Thouare (SVR g-17-90, #l). A 15 mm laid chip seal: 1) use of a modified binder VTAC overlay had been placed on this and precoated chips virtually eliminates two-lane secondary road in July 1990. loose chips and allows immediate open- ing to traffic; 2) noise levels are lower The overlay mix is trade named than for conventional chip seals; and 3) it COLRUG, a proprietary product of the is suitable for a variety of traffic volumes. French paving contractor, COLAS S.A. COLRUG uses 5-percent SBS latex as the The members of the EAST inspected a bitumen modifier. The overlay appeared paver-laid chip seal constructed in July fresh and in excellent condition; EAST 1989 on route RN 171 near La Baule members did not note any distress. (SVR g-17-90, #7). This is a four-lane highway with an ADT of 25,000. The The second VTAC overlay was on route NOVACHIP chip seal system marketed N 165,30 km west of St. Nazaire; this is a by SCREG Routes Group was used in the four-lane, divided freeway carrying a high construction. The binder layer was an traffic volume. The 10-mm thick overlay emulsified, 60/70 penetration grade bitu- men modified with 5-percent Neofler (an
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SBS latex). The binder was applied at a Gussasphalt is placed at 200 to 250°C rate of 0.95 kg/m*; the chips were placed (390 to 4809) with a special screed at a rate of 25 to 30 kglm2. on a specially-prepared pavement surface. It may also be poured from The pavement had an open look, without buckets and “floated” with hand tools any apparent distress except for some in a manner similar to PCC. No com- minor tearing along the centerline of the paction is required; therefore, one m* driving lane. Considering the traffic of Gussasphalt surface course can be volume and loads, the group judged the laid with the same quality as 1 million m*. performance to be impressive. The fresh Gussasphalt surface is dressed with excess chippings at a rate of about Gussasuhalt (Germanv) 15 kg/m*; these are rolled into the hot surface with a heavy steel-wheeled Design, Cost, and Serviceability--The roller. The German specification for term “Gussasphalt” is difficult to translate Gussasphalt is contained in the ZTV precisely, but may be best approximated ~ 84, pages 47,48,50 and 51. as floated or pourable asphalt or bitumen mastic. In Germany, Gussasphalt is con- Figure 7 compares the gradation limits sidered a premium paving mix intended for a German O/llS Gussasphalt mix with for surface and wearing courses bearing those for the German O/llS SMA mix. As the highest traffic volumes and highly can be seen, the Gussasphalt aggregate channelized truck traffic. gradation is relatively rich in the middle FIGURE 7
80 - 70 - 60 - 50 -
0 I, Ill t I I IllIll I I I Ilrrll 0.05 .l 1 10 15 SIEVE SIZE, mm
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fraction (0.09 to 2 mm) and mineral filler surfaces. Most important, the high ( 0.09 mm) content compared with SMA. temperatures required for Gussasphalt In different terms, the coarse aggregate mixing and paving operations might lead fraction (retained on the 2 mm sieve) is to air quality concerns in the United typically 55 percent for Gussasphalt States. compared with 80 percent for SMA; the mineral filler fraction is a maximum of In-Service Pavements--The EAST 30 percent for Gussasphalt compared team closely inspected two in-service with only 15 percent for SMA. Gussasphalt pavements, one in the city of Hamburg (SVR g-12-90, #3) and the The bitumen content of Gussasphalt other in Lower Saxony (SVR g-12-90, #4). mixes may range from 6.5 to 8.5 percent by weight of the mix, depending on the The Gussasphalt pavement in Hamburg top size of the aggregate used and the was placed on the Behringstrasse in 1973. result of a specific permeability test. A This four-lane city street has a 40,000 low-penetration grade of bitumen is ADT with 6 percent heavy trucks; it is required, typically B 25 (25 penetration) one of several routes leading to and from or B 45. Given the high bitumen content a vehicular tunnel under the Elbe River. combined with the rich gradation, in- place air voids contents are close to The 40 mm thick Gussasphalt surface 0.0 percent. This is the essential charac- course was placed over an 80 mm HMA teristic of Gussasphalt; it prevents the binder course and 400 mm of treated base penetration of oxygen and the aging of material on a frost-proof sand subbase. the bitumen. The Gussasphalt overlay is in excellent condition; only slight rutting was noted Pavement structures incorporating here and there on the section of pave- Gussasphalt surface courses must be ment inspected. massively designed to distribute the loads transferred through the Gussasphalt The Gussasphalt surface course in Lower courses; otherwise, pavement rutting may Saxony was on the A-7 Autobahn north of eventually develop through deformation Kassel. This four-lane facility has a maxi- of the underlying courses. Well-designed mum seasonal ADT of 80,000, of which Gussasphalt pavements, however, are 17 to 20 percent are trucks. The 40 mm expected to perform satisfactorily for Gussasphalt surface course was placed in 15 years or more, and service lives of May 1990 over an 80 mm HMA binder 20 years or more do not appear course and a 180 mm asphalt base course. uncommon. The binder in the Gussasphalt was modi- fied with Trinidad Lake asphalt at a rate This longevity does not come without of 33 percent by weight of the binder or costs. Typically, the bid price of a about 2.2 percent by weight of the Gussasphalt overlay is almost 200 per- mixture. cent that of a conventional HMA overlay. Gussasphalt surfaces are much noisier than either SMA or conventional HMA
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The pavement did not show any apparent Department of Transport specification distress. The surface appeared rough, but CL.930. Nominal aggregate top sizes of this is considered normal because of the 1.5, 1.0, and 0.75 inches are specified. rolled-in chips. The wheel paths had a Compared with HRA, a DBM employs a smoother overall appearance. Some areas softer bitumen and lower fines content. It appeared ravelled, but this may also be depends markedly on mechanical inter- related to the rolled-in chips. lock of the aggregate for strength and resistance to load-induced stresses. The EAST team examined other Gussasphalt pavements briefly at loca- A mixture designated 30%-HRA is used tions on the A-7 and A-61 Autobahns. for wearing courses. The bitumen content These were 10 to 20 years old and were in is about 8 percent; a 50 penetration bitu- satisfactory condition. In several cases, men is used. Of the mineral aggregate, the Gussasphalt was rutted in the driving 30 percent is crushed stone retained on lane; this was explained as a failure in the the #7 sieve; the top size aggregate is underlying binder course. On the A-3 nominally 0.5 in. Another 55 percent is Autobahn, the group observed a 10 year sand and 10 percent is limestone mineral old Gussasphalt overlay on a PCC pave- filler (passing the #200 sieve). Design air ment. Other than some transverse crack- voids are about 4 percent. The mixture is ing, this pavement was also in satisfactory dressed with precoated inch chips rolled condition. into the surface at a rate of 12 to 13 kg/m2 to improve durability and skid resistance. Hot-Rolled Asuhalt and Bitumen 30%-HRA is considered a functional Macadam (United Kingdom1 alternative to SMA with the bitumen content providing the necessary cohesive Mixture Designs--For heavy duty service element in the mix. on motorways and other trunk routes carrying high traffic volumes and substan- A mixture termed 60%-HRA is used for tial truck traffic, the typical pavement road base layers. This mixture has a bitu- structure in the United Kingdom includes men content of about 5.6 percent and it various types of hot-rolled asphalt and also employs a 50 penetration-grade bitumen macadam. bitumen. Sixty percent of the mineral aggregate is crushed stone retained on Hot-rolled asphalt is the general term for the #7 sieve; the nominal top size a gap-graded mixture meeting British aggregate is in. Standard BS594. The bitumen-filler mortar and the sand fraction provide Dense bitumen macadam and its variants mechanical strength; the bitumen content are employed principally for road base provides cohesion. A hard, low penetra- and subbase course. For example, heavy tion grade bitumen is used as the binder. duty bitumen macadam (HDM) has a continuously-graded aggregate with a top Dense bitumen macadam (DBM) is a size of 1.5 inches, but has a bitumen con- general term for a continuously-graded tent of 3.5 percent compared with 4.0 to mixture meeting United Kingdom 4.5 percent for DBM. A DBM that uses a
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50 penetration grade bitumen in place of Reconstruction of the southbound lanes the usual 100 to 200 penetration grade is of the M-l was prompted by deflection termed DBM 50. measurements; the existing northbound lanes showed little apparent distress. The At smaller thicknesses than DBM, pave- motorway was constructed in 1969 and ment layers of HDM and DBM 50 pro- overlaid in 1981 with a 40 mm HRA vide equal service. All other things being wearing course. Traffic volume is 60,650, equal, relative thicknesses of 1.00,0.90, including 25 percent trucks. and 0.88 for DBM, DBM 50 and HDM, respectively, provide equal resistance to Major reconstruction was taking place in traffic loads. the left-hand driving lane (#l of three) where 300 mm of the existing pavement Structural Design Incorporating HRA was milled out with a cold planer. The and DBM Mixes--A currently favored milled-out material was replaced by four pavement structure for heavy service on pavement layers, including a 40 mm 30%- motorways and trunk roads uses a 30%- HRA wearing course, 215 mm of HDM HRA wearing course, an HBM upper upper road base, 125 mm of 60%-HRA road base, and a 60%-HRA lower road lower road base, and 100 mm of DBM base over a substantial combination of subbase, for a total depth of 380 mm over bound and unbound subbase and sub- the existing 300 mm graded limestone grade courses. This structure is designed subgrade. to provide resistance to deformation in the upper courses while simultaneously The EAST members witnessed providing resistance to tensile stresses in construction of the upper road base on the bottom layers. the #l lane. Two conventional pavers with fixed screeds were in use; laydown Severe rutting of HRA wearing courses temperature was 160°C on a cold, windy did not occur during the unusually hot and intermittently rainy day. Daily ton- summer of 1990 when pavement temper- nage was about 5,500, requiring 100 haul atures as high as 50°C (122’F) were com- trucks to continuously supply hot-mix for mon throughout the United Kingdom, the pavers. The total reconstruction of although this temperature is near the 9 km of six-lane pavement will cost about (ring and ball) softening point of the $8 million or about $34.25 per square bitumens used. yard.
Construction--The EAST team observed The M-40 extension is completely new construction of heavy duty pavements on construction. This six-lane facility will two motorway projects in the United have an initial pavement 510 mm in depth Kingdom: reconstruction of the M-l comprised of a 40 mm 30%-HRA wear- motorway near junction 27 north of ing course, a 195 mm HDM upper road Nottingham (SVR g-20-90, #l) and base, a 125 mm 60%-HRA lower road construction of a new section of the M-40 base, and a 150 mm subbase prepared north of Oxford (SVR g-20-90, #2).
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from better quality crushed rock. This with a chip spreader at a rate of 12 to structure is placed on a prepared 13 kg/m2 and rolled with three rollers to subgrade of 600 mm of crushed rock. achieve firm anchoring.
The EAST team also observed construc- The HRA wearing course mix was being tion of an HRA wearing course on the #3 produced on site, but road base mixes outer passing lane. Laydown was with a were hauled almost 2 hours from a conventional paver at 160 to 170’C. After remote location to take advantage of compaction of the HRA, the crew imme- better quality aggregate. Up to 20,000 diately applied 20 mm of precoated chips tons of road base mix was being laid each week.
OTHER SPECIAL, PURPOSE MIXES In Germany, an application of a Ralumac earlier reconstruction projects, but had slurry seal was observed by the EAST presented problems with bitumen team (SVR g-13-90, #l). This proprietary compatibility and separation. Further- system, which is used in the United more, the SBS and EVA-modified States, employs a latex-modified, pavements failed under heavy, static tire emulsified bitumen. loads.
In Denmark, the EAST members Two other special-purpose overlay witnessed taxiway reconstruction at the systems based on SBS latex-modified Kastrup Airport, Copenhagen (SVR bitumens were observed in France. g-11-90, #l). The HMA binder course BETOFLEX is a proprietary, that was being laid was modified with a deformation-resistant overlay for bridge combination of Microfil carbon black, decks. A 1 year-old overlay was inspected hydrated lime, and cellulose fibers. The on the Anne de Bretagne Bridge in carbon black was intended principally to Nantes (SVR g-17-90, #4). flatten the temperature-viscosity response of the binder; it also has been found to Construction of a two-layer overlay slow the aging of the bitumen during specially designed to prevent reflective hot-mix production. cracking was observed on route RN 165 near Sautron (SVR g-17-90, #6). Both Personnel of the Copenhagen Airports the SAFLEX wearing course and the Authority noted that both SBS latex and RUFLEX binder course use SBS EVA7 had been employed as modifiers in latex-modified bitumen.
7 EVA = Ethylene Vinyl Acetate.
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MIXTURE DESIGN TECHNIQUES AND TEST APPARATUS
Novel Mixture Desbn Techniaues France--In France, the LCPC mix design system is universally employed by the Germany--As noted in the section on central road authority and the paving SMA in Germany (page 72), mix designs contractors. Compactors and a battery of for the surface and base courses on each sophisticated mechanical engineering test project in Germany are selected from a equipment are used to measure the per- series of standard designs. These have formance characteristics of the trial mixes been developed through experience for (resistance to rutting, fatigue cracking, different traffic volume classes. How- and moisture sensitivity). The two types ever, the Marshall mix design method is of compactors in use are gyratory, which used extensively for voids analysis and the is similar to equipment used by the U.S. selection of target bitumen contents. Army Corps of Engineers, and rolling wheel. (Resistance to low-temperature This approach requires careful selection cracking is not specifically addressed). of materials, tight control of all variables in the hot-mix production process and, General Procedures--The procedure generally, a rigorous adherence to all varies according to the knowledge avail- requirements of the specification. It also able on the mix to be used. If the mix demands strict attention to pavement has been used with the same material drainage requirements and universal composition, the gyrator-y shear testing provision of frost-proof foundations for machine is used for verification to assure all classes of pavement structures. the mixture’s workability has not chang- ed. If one or two of the material com- During construction, the contractor is ponents are new, verification is per- required to conduct quality control formed regarding workability using the measures according to the specifications gyratory shear testing machine; the for the project. Furthermore, loose mix DURIEZ test similar to the U.S. samples are taken on behalf of the State immersion-compression procedure, is road authority from the hopper of the used for compressive strength and paver and checked for satisfactory bitu- resistance to immersion. men content and aggregate gradation by an independent, fJlird-party laboratory. If the mix design employs materials of Cores are also taken from the new pave- unknown performance, a complete ment to determine that requirements for battery of tests is performed, including compaction, air voids content, and bond verification of mixture workability by between layers have been met. gyratory shear testing, compressive strength and resistance to immersion in water, wheel tracking test, and direct
European Asphalt Study Tour 1990 98 tension test. On occasion, when an consideration is given not only to the rut asphalt contractor develops a new depth occurring after a certain number of proprietary mix, the complex modulus cycles at a specified void content at the and fatigue tests are used instead of the job site, but to the cross-section of the direct tension. rutted specimen and the sensitivity of this curve to a variation in air void content. Initial screening of candidate mix designs The equipment also allows the specimen is done by compaction with the gyrator-y to be conditioned by exposure to water so shear testing machine to select a trial mix that moisture sensitivity can be estimated. within the desired air voids content range. Empirical relationships have been devel- Fatigue Cracking--Because tests for oped that correlate the laboratory air fatigue cracking characterization are voids content to that found in actual pave- costly and time consuming, they are ments. A rubber-tired, rolling wheel carried out only for research. The first compactor is then used to prepare plate type of fatigue test is an imposed dis- or slab specimens from which cylindrical placement alternating bend test. Four and trapezoidal beam specimens may be trapezoidal-shaped test samples may be cut for mechanical engineering testing. tested simultaneously. This test consists of maintaining constant displacement The rutting, stripping and load-related amplitude and frequency for the free end fatigue characteristics of trial mixes are of the test sample. During the test, con- determined with sophisticated wheel- tinuous reduction of the stiffness modulus tracking and direct tension testing equip- from accumulated fatigue damage is re- ment. These results are compared with a corded. This is reflected in a reduction in database of similar measurements on the force required to maintain constant field pavement specimens to gauge the displacement amplitude. The test is con- suitability of the trial mix design. tinued until the initial force required to impose displacement is reduced by Permanwt Deformation and Moisture one-half. Sensitivity--For permanent deformation, a wheel-tracking test is used. It measures A trend has emerged in France toward the rut created by the repeated passage of shear fatigue testing. This test is also run a wheel over a prismatic asphalt concrete at imposed strain amplitudes. The shear sample. The French strongly believe that fatigue test provides results showing less the laboratory simulation of the rutting scatter than the bending fatigue test. It phenomenon must approach actual pave- also takes more effective account of the ment stress conditions so the result ob- types of load to which thin surface tained can provide one of the selection courses and interlayers are subjected. In criteria for a mix design. connection with current research, this test is being used in France to study the The equipment provides for testing two capacity of asphalt concretes for self-repair during periods at rest and the samples simultaneously at a fixed temp- laws of damage accumulation. erature. To evaluate rutting sensitivity,
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A single-axle direct tensile load test has Test Specimen Fabrication and been developed for comparing the fatigue Compaction--Although roller compaction resistance thickness design of asphalt (rolling wheel device) simulates site com- concretes, where the critical stress in the paction equipment, this device is not pavement layer concerned may be assimi- considered suitable for the routine manu- lated to a tensile load. Strain, the form of facture of specimens necessary for a which is parabolic over time, is applied. widely acceptable method of mix design. It is first applied in a minor strain field to define the moduli dependent on time and The University of Nottingham has iden- temperature. Then it is applied in a tified a procedure that uses the PRD test major strain field to the point of rupture apparatus to manufacture test specimens, to deduce a linearity loss. Definition of a make the use of large aggregate easier, simplified test procedure incorporating and introduce a kneading compactive several tests and carried out on a single effort. The procedure involves a 6-inch sample substantially reduces cost and diameter split mold and a vibrating ham- makes it possible to use the test in routine mer. The PRD test is widely used in the mix design. United Kingdom to determine the degree of compaction of materials laid on site. United Kingdom--In the United King- Therefore, this test apparatus was dom, the Marshall design method is used adopted as the laboratory procedure. by some county road authorities while others rely on standard recipe designs By varying the time and the temperature that have performed well. Historically, at which the specimen is compacted, a use of the Marshall design method began range of PRD’s for each mix formulation because pavements constructed with can be obtained. Initially, three levels of recipe mixes experienced severe rutting compaction conditions are used to during the extremely hot sumrner of 1976. achieve 100,96 and 93 PRD.
This situation has led to a proliferation of Volumetric Analysis--The -volumetric “standard” rnix designs--more than 200 proportions of the materials are impor- variations, extant, that met the umbrella tant parameters that influence the mech- specification requirements for HRA and anical performance of mixes. Ranges for DBM discussed on page 94. these parameters are specified as part of the mix design process and as a prelim- The University of Nottingham has inary step before mechanical testing. developed a more performance-oriented design method that characterizes the The control variables used are: VMA, mechanical behavior of trial mixes using voids in the mineral aggregate;Vv, voids repeated load indirect tensile, uniaxial in the mix; and VB, volume of asphalt in creep, and repeated load axial tests. Com- the mix (similar to VFA in United States paction of cylindrical trial specimens practice). For mixes compacted to 100 employs a specially-adapted vibratory PRD, the mix properties should be within hammer called a PRD or percentage the following limits to maintain satisfac- refusal density apparatus.
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tory fatigue strength: VMA, 13 to 18 per- The test is terminated at 3,600 cycles or cent; Vv, 3 to 8 percent; and VB, 8 per- earlier if specimen failure appears cent or greater. irnminent. Precise interpretation of results from this test is not yet possible. Mechanical Engineering Tests--Mixes The results, however, will clearly rank that meet the established volumetric materials in order of their deformation property criteria are then subjected to resistance and engineering judgment will mechanical engineering tests to estimate help in the decisionmaking process. At their probable performance in pave- this stage, satisfactory mixes should not ments. These tests require special equip- exhibit more than 1 percent strain at the ment, which is necessary to assess end end of the test. product performance of bituminous mixtures. Tests for fatigue strength are not recom- mended; this testing requires an excessive The equipment advocated for this pur- number of test specimens for reliable pose is the Nottingham Asphalt Tester, results. The minimum VB of 8 percent is which is an all-in-one test apparatus designed to avoid mixes that may be sus- capable of performing indirect tensile ceptible to cracks. The fatigue strength of tests, static load creep tests, repeated load the optimum mix formulations may be axial tests, and fatigue tests. For design, checked by using a prediction method two tests are used: the indirect tensile test involving the softening point of the bind- to obtain elastic stiffness and the uncon- er and the volume of binder in the mix fined repeated load axial test to assess (VB). This method is considered to be of resistance to deformation. use when the results are combined with pavement design calculations using the The indirect tensile test is performed first mechanistic approach. because it is non-destructive. Values of elastic stiffness should not be less than The final check is the durability of the 2,000 MPa at 20°C. Generally, speci- selected mix. The indirect tensile test is mens with satisfactory volumetric pro- performed on a specimen at the optimum portions will have elastic stiffnesses in mix formulation after immersing the excess of this value. specimen in water for 24 hours at 25’C. If the elastic stiffness is within 70 percent The unconfined repeated load axial test of its pre-immersed original value, the has adopted the conditions of the static mix is satisfactory. If it fails this criterion, creep test (100 kPa load at 40°C applied the binder content must be increased. for 1 hour), but the load is pulsed onto the specimen at a frequency of 0.5 Hz.
NOVEL TEST APPARATUS Compaction Devices--As discussed in the compaction devices in European mix “General Remarks” found on page 90, the design and analysis systems. A use of gyratory and rolling-wheel compaction device similar in size and
European Asphalt Study Tour 1990 101 capabilities to the well-known U.S. Army hammer is used extensively by the high- Corps of Engineers device and termed a way community in the United Kingdom Gyratory Shear Compacting Press is for soil tests, a fact that should facilitate employed in the LCPC design method. its adoption in a laboratory mix design The device is commercially available and field quality control system. from the French manufacturer MAP, with a retail cost in France of 230,000 Ffr Compared with current practice in the (about $43,000). United States, the gyrator-y and rolling wheel compaction devices discussed here The LCPC method also requires the use represent substantial increases in equip- of a rubber-tired rolling wheel compac- ment costs and complexity of operations. tor, termed a Plate Compactor. This In particular, the rolling wheel compac- device mounts single or dual 0.415 m tors produce large, massive slab speci- diameter by 0.109 m wide tires, and can mens; high-volume batch mixers are achieve a loading pressure of 700,000 Pa. needed to produce the HMA required, It requires the use of an 80 kg batch mixer and forklift trucks are necessary to move and produces compacted slabs in 20 min- the specimens. Finally, the rolling wheel utes. Maximum slab size is 0.6 m long, compactors produce slabs from which the 0.4 m wide and 0.15 m high. Cylindrical actual test specimens must be cored or specimens are typically cored horizontally sawn, depending on the test configura- from the slab, allowing specimen lengths tion. near 0.6 m. This apparatus is also avail- able from MAP at a cost of about 250,000 Mechanical Engineering Test Ffr ($46,000). Devices--The LCPC design method discussed on page 97 employs two In the United Kingdom, both the TRRL engineering test devices that are unknown and the University of Nottingham have in routine U.S. mix design practice. one-of-a-kind rolling wheel compaction devices that are used principally for The Pavement Rutting Tester is a wheel research studies. These employ a partial tracking device in which two rubber-tired segment of steel wheel, similar to those wheels are driven in back-and-forth employed on steel-wheeled pavement motion over a rectangular slab prepared rollers, to provide the compactive effort in the laboratory or cut from a field needed for slab production. These are not pavement. presently available from commercial sources. The dependence of the rut depth in the specimen with material types, number of The PRD test apparatus employed for loading cycles, tire pressure, wheel load, laboratory compaction in the University temperature, and moisture conditioning of Nottingham (or Brown-Ackroyd) Mix can be determined. An extensive data Design System is a cornmercially-avail- base is available to relate the measured able vibratory hammer that produces rut depths obtained in the test to those 6-inch diameter cylindrical mix specimens expected in actual field pavements. This in split steel molds. This type of vibratory
European Asphalt Study Tour 1990 102 apparatus is available commercially from Similar devices are used in many research the French manufacture MAP at a cost of laboratories in the United States and 250,000 Ffr ($46,000). Europe.
Wheel-tracking test devices of various The Nottingham Asphalt Tester, which sizes and degrees of complexity are also was discussed on page 99, combines used in the United Kingdom for research several test devices into one computer- studies and to calibrate, for field perform- controlled assembly. The apparatus is ance, the results of such other methods as capable of performing indirect tensile static and dynamic creep tests. These tests, static load creep tests, repeated devices are not used directly in mix design load axial tests, and fatigue tests. For the and analysis systems. They generally Brown-Ackroyd mixture design proce- employ pneumatic rubber-tired wheels dure, only two test procedures are rout- like the LCPC device, but in some inely used: the indirect tensile test to instances, steel wheels or hard rubber- obtain elastic stiffness and the uncon- tired wheels are used. fined repeated load axial test to assess resistance to deformation. The LCPC method further incorporates the use of the Fatigue Bend Machine for The functions contained in the Notting- Bituminous Mixes. This machine carries ham Asphalt Tester are used extensively out fatigue tests on trapezoidal beam around the world for research studies, but specimens cut from laboratory-compact- have never before been integrated into a ed slabs or actual pavements. The beam is complete design procedure in this way. loaded repeatedly at a nominal excita- Many of the individual pieces of test tion frequency of 25 Hz. For various mat- equipment, particularly the indirect ten- erial combinations and temperatures, the sile test device, are available in state dependence of the number of load cycles highway agency laboratories in the to specimen failure or some predeter- United States. mined reduction in stiffness modulus is determined. This method also is calibrat- Agencies considering adoption of this ed to an extensive data base of French design procedure, but that do not have pavement performance, but because of its any of the component apparatus avail- complexity, is run only when completely able, can obtain the complete Asphalt new or unfamiliar materials and mix Tester from commercial sources in the designs are evaluated. Commercially, this United Kingdom for approximately apparatus is available for about $50,000. $140,000.
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REFERENCES Liljedahl, B., Heavy-Duty Asphalt Smith, R.W., Rice, J.M. and Spelman, Pavements, in the Proceedings of a . S.R., Design of Open-Graded Asphalt Seminar, aminous199Qs Roads m h , Friction Courses, FHWA Report No. The Irish Branch of the Institute of FHWA-RD-74-2, Washington, D.C. Asphalt Technology, Dublin, Ireland, 1 January 1974. November, 1990.
European Asphalt Study Tour 1990 APPLICATION OF FINDINGS 107
APPLICATION OF FINDINGS As described throughout this report, the in adapting the EAST’s findings for use in EAST’s mission of identifying potentially the United States through carefully promising asphalt technologies and con- designed experimental plans. tract administration practices was consid- ered by all participants to be an over- After returning from Europe, members of whelming success. But identifying new the EAST met to consider, first, which technologies is not enough. The success- European technologies should be focused ful adaptation of those findings for poss- on initially and then to develop a plan for ible use in the United States will be the the application of their findings. After determining factor in measuring the considering all the possibilities, the study mission’s success. team identified four general areas and several specific areas: While immediate implementation of the findings is desired, caution must be exer- Asphalt Pavement Mixtures: cised. The United States cannot just “hit Stone Mastic Asphalt the ground running” with Europe’s meth- Porous asphalt ods. For special reasons, these technolo- Modified Binders gies may work well in Europe and not as well or as efficiently in the United States. Laboratory Equipment Cultures are different. For example, one Mix Design Equipment noticeable fact in Europe is the limited Laboratory Compaction amount of litigation in the transportation Rut Tester industry. In Europe, a close and exten- Innovative Contracting Practices sive working relationship exists between Lane Rental government and private industry. While Contractor Warranties/Guarantees this situation may be due partly to legisla- tion or regulation, it does exist and offers Research more opportunities than in the United States for cooperative ventures in the The members then developed an development and implementation of experimental plan for implementing their technology. For these and other reasons, findings: patience and persistence are paramount
ASPHALT PAVEMENT MIXTURES
Stone Mastic AsDhalt tions has been assigned the lead in coor- dinating evaluation of this technology, Stone Mastic Asphalt is a special purpose, adapting it to this country’s needs and rut resistant surface pavement mixture of construction characteristics, and imple- coarse aggregates held together by an menting it in the United States. To asphalt-filler-stabilizer mastic. The accomplish these assignments, the Office FHWA’s Office of Technology Applica- prepared a work plan that describes a
European Asphalt Study Tour 1990 108 series of field tests in five or more States; Material sources have been identified for collection and refinement of existing the Michigan pilot project. The State’s information to include a followup Euro- and the FHWA’s laboratories have begun pean trip; material, mix design, and con- preliminary material and design investi- struction evaluation; and a detailed study gations. Laboratory activity will also of SMA’s mechanical and physical examine the effectiveness and composi- properties. tion of such SMA stabilizers as cellulose, mineral fibers, and various polymer/ Existing reports and data on SMA have elastomer modifiers. been reviewed and a Technology Syn- thesis on the subject has been released. The NCAT has submitted a proposal to The technical fact-finding visit focused on establish SMA’s characteristics and eval- SMA in Germany and Sweden was com- uate its sensitivity to changes in its com- pleted in late April. Inquiries during the ponents. This effort, lasting 3 months, visit focused on mixture design and will primarily concentrate on the material controls for material and construction. being used in the Michigan pilot project. Samples of SMA materials planned for projects in this country will be provided Initial and periodic post construction to European experts for evaluation. evaluations will be performed on the Georgia and Michigan pilot projects. A Technical Advisory Committee (TAC) Data from additional field projects along has been established and information on with State, FHWA, and industry labora- the technology distributed. Membership tory research will be pooled and analyzed in the TAC includes representatives from for eventual national implementation of seven States, FHWA, SHRP, NAPA, The SMA. Asphalt Institute, and the National Cen- ter for Asphalt Technology (NCAT). The Porous Asphalt seven States are Colorado, Georgia, Michigan, Missouri, Texas, Virginia, and European PA pavements are similar to Wisconsin. A formal meeting of the TAC the open-graded friction courses used in will be scheduled to coincide with the the United States. They provide a pave- construction of an initial State field ment surface that drains rainwater rapid- project. ly, thus reducing the incidence of hydro- planing. European PA also provides a Proposals have been received for field means of absorbing and dissipating noise. projects in Georgia and Michigan. Con- The use of modified asphalt cements struction is scheduled for mid to late (cellulose, mineral fibers, and polymers) summer. An additional project is being in the European PA allows for increased planned in Wisconsin, with several other asphalt film thickness, thus reducing States expressing interest in constructing aging while enhancing durability. SMA pavements, pending results of the pilot projects. Use of open-graded friction courses with modified asphalts, similar to the Euro- pean PA, is being examined for possible
European Asphalt Study Tour 1990 109 field evaluation and implementation. cation. The guidelines will include uni- Projects are planned for the summer of formity in the classification of modifier 1991 in several States using this types, test methods for evaluating the methodology. modifiers, life-cycle cost effectiveness, methods of acceptance, and potential Modified Asuhalt Binda specifications.
European practice routinely uses a wide Evaluation and implementation of these range of modified asphalt cements in modifications will, in part, take place construction of roadway wearing surfaces. through our efforts in the areas of SMA The Office of Technology Applications is and PA. examining an approach and formulating guidelines for a study on asphalt modifi- LABORATORY EQUIPMENT
Mix Desbn Eauiument ales, and equipment. These systems will then be used in developing and testing Representatives from the FHWA, the methodologies for mixture design in this Colorado Department of Highways, and country. the NAPA will jointly investigate the flex- ible pavement design testing technolo- Comuaction Devices gies used in Europe. They developed a work plan that addresses equipment The FHWA will evaluate such European acquisition, installation, staffing, training, compaction testing devices as the rolling test and evaluation, and ultimate wheel compactor and the British vibra- implementation in this country. tory hammer. Data generated on these devices will be compared with existing The work plan focuses on mix design sys- United States compaction methodology tems from France and the United King- (Marshall), gyrator-y compaction devices dom. The French system incorporates (Corps of Engineers and Texas), and two types of compactor, namely gyrator-y modified Marshall hammers. (similar to equipmentused by the U.S. Corps of Engineers) and rolling wheel, as Rut Tester well as a series of mechanical tests to measure trial-mix performance charac- The French wheel tracking device will be teristics. The University of Nottingham evaluated and compared with current rut in the United Kingdom has developed an prediction methodologies, as evidenced asphalt tester that is an all-in-one test in the current Asphalt Aggregate Mixture apparatus capable of performing indirect Analysis System. Comparisons will also tensile, static load, creep, repeated axial be made with the Georgia rut-test device load, and fatigue tests. The evaluation of being evaluated in six States. these two systems will include examina- tion of the various methodologies, ration-
European Asphalt Study Tour 1990 110
INNOVATIVE CONTRACTING PRACTICES The TRB established Task Force A2T51 mental Project 14 to address the call. in 1987 to address innovative contracting Now that the project has been announc- practices. That task force was charged ed, the FHWA is seeking--and strongly with soliciting, studying, and compiling encouraging--additional State DOT information on the practices under which interest. the United States and foreign agencies contract for construction as they affect A number of activities the members of quality, progress, and costs; call attention the EAST observed in Europe are sup- to practices that inhibit quality construc- portive of Task Force A2T5 l’s findings, tion and ways to counter them; and sug- including time/lane rental bidding, con- gest ways for improving contracting pro- tractor responsibility factors (quality and cesses with attendant quality improve- performance), design/build, performance- ment in construction. The members of based specification and testing, alternate Task Force A2T51 plan to publish a bids, regional testing/product evaluation report on innovative contracting practices centers, and warranties/guarantees. in 1991. The report will contain signifi- cant findings on bidding, materials, Moreover, the proposed Surface quality, and insurance/bonding. Transportation Assistance Act of 1991, which the President submitted to the In 1989, Task Force A2T51 asked the Congress in February, contains provisions FHWA to establish a mechanism for directly related to one of the group’s assisting State departments of transpor- findings. The bill would, for the first tation (DOT) in evaluating and validating time, allow State DOT’s to request some of the Task Force’s early findings. warranties/guarantees from contractors The FHWA established Special Experi- on Federal-aid projects. RESEARCH Research is another area where the research process must be realigned to European practice may offer an oppor- strengthen our competitiveness in inter- tunity for enhancement of the U.S. national markets. It must be adrninis- industry/government/academic research tered to strengthen and foster innovation, and development relationship. In instead of deterring or stifling the quest Europe, government and industry have for innovation, as is the case with some extensive research facilities, and the current practices. results are marketed aggressively. In some countries, in fact, research and Contracting practices in the United marketing are joint ventures between States, in contrast with those in Europe, government and industry. tend to discourage contractors from operating large-scale research facilities. The FHWA and the State DOT’s must One primary reason is size. European take a fresh look at the way research is countries generally work with a few large conducted in the United States. The contractors. Another reason is the oppor-
European Asphalt Study Tour 1990 111 tunity in Europe to reward innovation Research Advisory Cormnittee to identify through such contracting practices. as the capabilities and facilities of the design/build and warranties/guarantees. United States highway community Regardless of the differences, research through an inventory of academic, gov- and development must be given as high a ernment, and industry resources. This priority in the United States as it is in inventory is the first step toward a nation- Europe if economic competitiveness in al consortium of highway research labora- the world market is to be maintained. tories similar to research laboratories in Europe. In addition, fostering a cooper- In addition, the United States needs more ative, collaborative environment among cooperative research between govern- industry and government is important if ment and private sector laboratories. the United States is to fully use the cap- Such an arrangement could lead to lower abilities and results of the national research and development costs by mini- research and development resources mizing duplication of specialized scienti- without significant concerns about fic expertise and expensive laboratory ownership turf. facilities and equipment. To this end, efforts are underway through AASHTO’s
European Asphalt Study Tour 1990 ACRONYMS, DEFINITIONS and TECHNICAL TERMS 115
ACRONYMS, DEFINITIONS and TECHNICAL TERMS
ACRONYMS DEFINITIONS/TECHNICAL TERMS
AASHTO ANAS - Azienda Nazionale Autonoma American Association of State delle Strada - the National Road Board, Transportation Officials an asphalt plant (in Italy) 444 North Capitol Street, NW., Suite 225 Washington, D.C. 20001 BAST - Bundesanstalt fur Strassenwesen - Phone (202) 624-5800 the Federal Highway Research Center (in Germany) FHWA Federal Highway Administration DBM - Dense Bitumen Macadam 400 Seventh Street, SW. Washington, D.C. 20590 EVA - Ethylvinyl Acetate Phone: (202) 366-0660 HABS - Swedish term for SMA NAPA National Asphalt Pavement Association NAPA Building, 5 100 Forbes Boulevard HABT - Swedish term for conventional, Lanham, Maryland 20706-44 13 continuously-graded asphalt concrete Phone: (301) 73 l-4748 HMA - Hot-Mix Asphalt SHRP Strategic Highway Research Program HRA - Hot Rolled Asphalt 818 Connecticut Avenue, NW., Suite 400 Washington, D.C. 20006 LCPC - Laboratoire Central des Ponts et Phone: (202) 334-3774 Chaussees - the Central Laboratory of Bridges ad Roads (in France) TAI The Asphalt Institute PA - Porous Asphalt Research Asphalt Drive P.O. Box 14052 PCC - Portland Cement Concrete Lexington, Kentucky 405 12-4052 Phone: (606) 288-4960 SBS - Styrene-Butadiene-Styrene TRB Transportation Research Board SMA - Stone Mastic Asphalt 2101 Constitution Avenue, NW. Washington, D.C. 20037 TRRL - Transportation Road Research Phone: (202) 334-2989 Laboratory
European Asphalt Study Tour APPENDIX A FHWA/AASHTO/NAPA SITE VISIT REPORT DATE 9-10-90 #I DESCRIPTION OF NOVEL PAVEMENT FEATURE:
STONE MASTIC ASPHALT (S&M): Tradename Stabinor produced by skanska AR.
LOCATION (COUNTRY, LOCAL GOVERNMENT UNIT, HIGHWAY #, MILEPOST):
Tingstad Tunnel (east side), Route E6, Gothenborg Sweden
DATE OF CONSTRUCTION I985 LENGTH (mi/km) # OF LANES 3 (east bound)
ACTUAL ADT % TRUCKS EALS WHEN OPENED ACTUAL CURRENT 100,000 (6 lanes) DESIGNED BRIEF DESCRIPTION OF PAVEMENT STRUCTURE (# OF LAYERS, LAYER THICKNESSES, etc):
38 mm overlay of 80 stabinor 12 (80 kg/m’, I2 mm top size).
ASPHALT CONTENTm(% OF MIX) AIR VOIDS CONTENT a(%)
MODIFIER TYPE Mineral Fiber MODIFIER CONTENT 0.8(% OF BINDER) AGGREGATE DESCRIPTION (GRADATION, MATERIAL TYPES, etc.):
TOP SIZE: 12mm; 50 % Quartzite typical gradation: 26% passing 2mm, 30 % passing 4mm, 50% passing 8mm, 10% filler passing 0.075mm (#200 sieve).
DISTRESS TYPE EXTENT OR FREOUENCY LOW MEDIUM HIGH
RUTTING 1 17mm
LONGITUDINAL CRACKING 1 X
TRANSVERSE CRACKING 1 X I RAVELLING IX ALLIGATOR CRACKING IX BLOCK CRACKING lx POTHOLES lx I
NARRATIVE DESCRIPTION OF PAVEMENT CONDITION:
High traffic volume precluded stopping bus to view pavement. However, rutting due to studded tires was apparent in some areas, not in others. Pavement generally had a roughly-textured, overall appearance. No other distress of consequence apparent at speed of 50 to 70 km/hr.
(form continued on reverse side)/26 JUNE 90 DRAINAGE FACILITIES:
COMMERCIAL SOURCE (IF PROPRIETARY FEATURE):
Stabinor is the tradename for SMA produced by Skanska AB. Mineral filler, tradename Inorphil, is used as modifier.
OTHER REMARKS:
POST-VISIT DEBRIEFING NOTES:
To date, SM.4 has taken 20 percent more traffic than the conventional HMA overlay previously used which lasted 5 years before rehabilitation was necessary.
At 5 years service, HM had a rut depth of 25mm compared to 17 mm for SMA. A 20 percent increase in service life for SMA compared to HMA is projected.
APPLICABILITY TO U.S. PRACTICE:
High
COSTS RELATIVE TO CONVENTIONAL U.S. CONSTRUCTION PRACTICE:
Increased. Swedish authorities justify increased first cost by longer service life.
35 mm PHOTOS: NO YES ROLL # NEGATIVE #‘S VIDEOTAPE: NO- YES- CASSETTE # AUDIOTAPE: NO- YES- CASSETTE #
REPORTER(S): FHWA/AASHTO/NAPA SITE VISIT REPORT DATE 9-10-90 #2
DESCRIPTION OF NOVEL PAVEMENT FEATURE:
STONE MASTIC ASPHALT (SMA): Tradename Wacotop produced by the Swedish paving contractor NCC.
LOCATION (COUNTRY, LOCAL GOVERNMENT UNIT, HIGHWAY #, MILEPOST):
Stalhanskegatan., Gothenborg, Sweden
DATE OF CONSTRUCTION 198.5 LENGTH (mi/km) # OF LANES 2 (east bound)
ACTUAL ADT % TRUCKS EALS WHEN OPENED ACTUAL CURRENT 30,000 (4 lanes) DESIGNED
BRIEF DESCRIPTION OF PAVEMENT STRUCTURE (# OF LAYERS, LAYER THICKNESSES, etc):
38 mm overlay of 80 viacotop 12 (80 kg/m’, 12 mm top size).
ASPHALT CONTENTm(% OF MIX) AIR VOIDS CONTENT a(%)
MODIFIER TYPE Cellulose fibers MODIFIER CONTENT 0.3(% OF MIX)
AGGREGATE DESCRIPTION (GRADATION, MATERIAL TYPES, etc.):
TOP SIZE: 12mm; 50 % Quartzite; typical gradation: 22% passing 2mm, 31 % passing 4mm, 38% passing 8mm, 10.5% filler passing 0.075mm (#200 sieve).
DISTRESS TYPE EXTENT OR FREOUENCY LOW MEDIUM HIGH
RUTTING 1 10mm
LONGITUDINAL CRACKING
TRANSVERSE CRACKING
RAVELLING lx
ALLIGATOR CRACKING BLOCK CRACKING IX I I I POTHOLES lx I
NARRATIVE DESCRIPTION OF PAVEMENT CONDITION:
High traffic volume precluded stopping bus to view pavement. Pavement viewed at speed showed little or no apparent distress.
(form continued on reverse side)/26 JUNE 90 DRAINAGE FACILITIES:
COMMERCIAL SOURCE (IF PROPRIETARY FEATURE):
Viacotop LY the tradename for SMA produced by NCC. Cellulose fiber is used as modifier.
OTHER REMARKS:
Paving was done by the Gothenborg Street and Highway Department.
POST-VISIT DEBRIEFING NOTES:
APPLICABILITY TO U.S. PRACTICE:
High.
COSTS RELATIVE TO CONVENTIONAL U.S. CONSTRUCTION PRACTICE:
35 mm PHOTOS: NO YES ROLL # NEGATIVE #‘S VIDEOTAPE: NO-YES- CASSETTE # AUDIOTAPE: NO-YES- CASSETTE #
REPORTER(S): FHWA/AASHTO/NAPA SITE VISIT REPORT DATE 9-10-90 #3
DESCRIPTION OF NOVEL PAVEMENT FEATURE:
Porous Asphalt (PA): Tradename Drainor produced by Skanska AB. LOCATION (COUNTRY, LOCAL GOVERNMENT UNIT, HIGHWAY #, MILEPOST):
Brackevagen, Route 159, Gothenberg, Sweden
DATE OF CONSTRUCTION 1986 LENGTH (mi/km) # OF LANES 2 (westbound)
ACTUAL ADT % TRUCKS EALS WHEN OPENED ACTUAL CURRENT 25,000 (4 lanes) DESIGNED
BRIEF DESCRIPTION OF PAVEMENT STRUCTURE (# OF LAYERS, LAYER THICKNESSES, etc):
43 mm overlay of 90 Drainor 16 (90 kg/m: 16 mm top size).
ASPHALT CONTENT ‘5.0 (% OF MIX) AIR VOIDS CONTENT >1.5 (%)I
MODIFIER TYPE Mineral Fiber MODIFIER CONTENT 0.8(% OF BINDER)
AGGREGATE DESCRIPTION (GRADATION, MATERIAL TYPES, etc.): TOP SIZE: 16mm; 55 % Quartzite; typical gradation: IO-15% passing 2mm, 20-24% passing 4mm, 36- 42% passing 8mm, 60% passing 11.3mm, 4-6% filler passing 0.075mm (#200 sieve).
DISTRESS TYPE EXTENT OR FREOUENCY LOW MEDIUM HIGH
RUTTING 1 6-7mm I
LONGITUDINAL CRACKING IX I TRANSVERSE CRACKING
RAVELLING
ALLIGATOR CRACKING
BLOCK CRACKING lx POTHOLES IX I
NARRATIVE DESCRIPTION OF PAVEMENT CONDITION:
Pavement uses 16mm maximum stone size to increase resistance to studded tires. Pavement has a rough- looking surface; lots of aggregate show. Pavement was viewed at speed from bus; little or no significant distress was visible.
‘. Nominal (form continued on reverse side)/26 JUNE 90 DRAINAGE FACILITIES:
COMMERCIAL SOURCE (IF PROPRIETARY FEATURE):
Drainor is the tradename for porous asphalt produced by Skanska AB. Mineral filler (Inorphil) is used as modifier.
OTHER REMARKS:
POST-VISIT DEBRIEFING NOTES:
80 Drainor 12 showed inadequate resistance to studded tires. 90 Drainor 16 is about as resistant to studded tires as conventional HMA.
APPLICABILITY TO U.S. PRACTICE:
Uncertain
COSTS RELATIVE TO CONVENTIONAL U.S. CONSTRUCTION PRACTICE:
In Sweden, PA costs about as much as SMA, but resists wear comparably to HMA. PA costs are justified on a case-by-case basis where noise reduction and water drainage are- required.
35 mm PHOTOS: NO YES ROLL # NEGATIVE #‘S VIDEOTAPE: NO- YES- CASSETTE # AUDIOTAPE: NO- YES- CASSETTE #
REPORTER(S): FHWA/AASHTO/NAPA SITE VISIT REPORT DATE 9-10-90 #A
DESCRIPTIONOFNOVELTECHNOLOGY:
"Vikan" Asphalt Hot Mix Plant LOCATION (couw~Y,Loc~~ G~VERNMENTUNIT,HIGHWAY#,MILEPOST): Near Gothenberg, Sweden
DETAILSOFOPERATION:
This is a 240 ton/hour batch plant employed to produce HMA, SMA and PA. The plant can handle both cellulose and mineral jibers which are dispersed mechanically into the pugmill. Fibers may also be used in pelletized form with asphalt cement as the binder. It is not necessary to coat the fibers with asphalt cement in the pug mill.
(form continued on reverse side)/26 JUNE 90 OTHER REMARKS:
POST-VISIT DEBRIEFING NOTES:
APPLICABILITY TO U.S. PRACTICE:
COSTS RELATIVE TO CURRENT U.S. PRACTICE:
35 mm PHOTOS: NO YES ROLL # NEGATIVE #‘S VIDEOTAPE: NO-YES- CASSETTE # AUDIOTAPE: NO-YES- CASSETTE #
REPORTER(S): FHWA/AASHTO/NAPA SITE VISIT REPORT DATE 9-12-90 #I
DESCRIPTION OF NOVEL TECHNOLOGY:
Hot mix plant - Permanent Batch Operation (Operated by Hamburg Asphalt Geschag)
LOCATION (COUNTRY, LOCAL GOVERNMENT UNIT, HIGHWAY #, MILEPOST):
Nordersted, Germany (Northern Suburb of Hamburg)
DETAILS OF OPERATION:
1. Very compactly organized-operations are “enclosed” to a large degree. 2. Employs 15 hot aggregate bins. 3. Much of the process heat is supplied by recylced waste gases. 4. Much high quality stone is imported from Norway. 5. Has two drums for heating aggregate. In the first, virgin aggregate is heated and screened. Hot waste gases are directed to the second drum (at 300°C) to heat RAP to 120°C. Particulate matter from virgin aggregate is trapped in heated RAP or in a baghouse filter when RAP is not being used in mix operations. 6. Aggregate is stored in hot bins at 180°C. The use of 16 hot bins allows mix designs to be varied rapidly. The plant is computer-controlled and can produce 160 different mix designs at present. Mix recipes in computer can be altered only at central oftice; plant operators can only select among stored designs. Total hot bin storage is 360 tons; filler is stored in separate bin. 7. RAP is used in base course mixes up to 50% (20% in Hamburg), and in surface course mixes up to 15%. No RAP is used in SMA. 8. Aggregate is heated and screened at night. Hot-mix is prepared in 2.5 ton batches. Production rate is about 160 tons/hr. Yearly production is near 100,000 tons. Mix cost at plant varies from $40 to 70. 9. Mixing time is 20-30 seconds per batch for virgin materials, 50 seconds for mixes with RAP content. Total hot mix storage capacity is 560 tons in eight storage silos. 10. A 60-80 pen grade asphalt cement is used. No rejuvenating agents are employed in recylced mixes. 11. Plant operating tolerances are &OS-0.2% for asphalt content, +0.3% for aggregate gradation. 12. There is no strict control of the final asphalt properties in recycled mixes. However, stockpiles of RAP are sampled every 300 tons to check gradation, asphalt content and ring-and-ball softening point of the binder, RAP stockpiles are blended to maintain an average R&B softening point of 70°C for the recovered asphalt cement. 13. When SMA mixes are produced, cellulose fibers are added through the filler bin. 14. Plant staff is 6 persons.
(form continued on reverse side)/26 JUNE 90 OTHER REMARKS:
POST-VISIT DEBRIEFING NOTES:
APPLICABILITY TO U.S. PRACTICE:
COSTS RELATIVE TO CURRENT U.S. PRACTICE:
35 mm PHOTOS: NO YES ROLL # NEGATIVE #‘S VIDEOTAPE: NO-YES- CASSETTE # AUDIOTAPE: NO-YES- CASSETTE #
REPORTER(S): FHWA/AASHTO/NAPA SITE VISIT REPORT DATE 9-IO-90 #L
DESCRIPTION OF NOVEL PAVEMENT FEATURE:
SMA Under Construction (SKanska AB Stabinor) LOCATION (COUNTRY, LOCAL GOVERNMENT UNIT, HIGHWAY #, MILEPOST):
European Route E-4 near Varberg, Sweden, KP 51500
DATE OF CONSTRUCTION 9-10-90 LENGTH-(mi/km) # OF LANES Divided 4-lane
ACTUAL ADT % TRUCKS EALs WHEN OPENED ACTUAL CURRENT 13,000 25 DESIGNED BRIEF DESCRIPTION OF PAVEMENT STRUCTURE (# OF LAYERS, LAYER THICKNESSES, etc):
2” (uncompacted) SMA overlay: 90 Stabinor 16, compacted to 38mm.
ASPHALT CONTENTq,L(% OF MIX) AIR VOIDS CONTENT 3-4(%)
MODIFIER TYPE Inorphil MODIFIER CONTENT &(% OF BINDER)
AGGREGATE DESCRIPTION (GRADATION, MATERIAL TYPES, etc.):
TOP SIZE: 16mm; 20% qualified stone (46 kr/m2); nominal gradation: 25010 passing 2mm, 28% passing 4mm, 45% passing 8mm, 70% passing 12mm, 8% passing 0.075mm (#200 sieve).
DISTRESS TYPE EXTENT OR FREOUENCY LOW MEDIUM HIGH
RUTTING I
LONGITUDINAL CRACKING I
TRANSVERSE CRACKING I
RAVELLING I I ALLIGATOR CRACKING
BLOCK CRACKING
POTHOLES
NARRATIVE DESCRIPTION OF PAVEMENT CONDITION:
New; construction in progress. Asphalt cement grade: B85.
(form continued on reverse side)/26 JUNE 90 DRAINAGE FACILITIES:
COMMERCIAL SOURCE (IF PROPRIETARY FEATURE):
Stabinor is the tradename for SMA produced by Skanska AB. Mineral filler, trade named Inorphil, is used as modifier.
OTHER REMARKS:
POST-VISIT DEBRIEFING NOTES:
SMA was placed with conventional paver at 160°C. Compaction was accomplished with two steel-wheeled rollers. No vibration was employed. Rollers operated close behind the paver.
Rolling is intended to orient stone skeleton; little compaction of the mat is expected. SMA is placed over a thin, I2-16mm, leveling course.
The air temperature at construction was about 6o”F, sky partly cloudy and wind at about 10 to I5 mph. Rolling can continue until mat temperature falls to 75°C. Second roller is equipped with infrared thermometer.
APPLICABILITY TO U.S. PRACTICE:
High
COSTS RELATIVE TO CONVENTIONAL U.S. CONSTRUCTION PRACTICE:
35 mm PHOTOS: NO YES NEGATIVE #‘S VIDEOTAPE: NO- YES- AUDIOTAPE: NO- YES- CASSETTE #
REPORTER(S) : FHWA/AASHTO/NAPA SITE VISIT REPORT DATE 9-10-90 #6 DESCRIPTION OF NOVEL PAVEMENT FEATURE:
SMA
LOCATION (COUNTRY, LOCAL GOVERNMENT UNIT, HIGHWAY #, MILEPOST):
European Route E-4 South of KP 51500 (see #5)
DATE OF CONSTRUCTION 1989 LENGTH (mi/km) # OF LANES Divided 4-lane
ACTUAL ADT % TRUCKS EALs WHEN OPENED ACTUAL CURRENT 13,000 25 DESIGNED
BRIEF DESCRIPTION OF PAVEMENT STRUCTURE (# OF LAYERS, LAYER THICKNESSES, etc):
ASPHALT CONTENT-(% OF MIX) AIR VOIDS CONTENT -(%)
MODIFIER TYPE MODIFIER CONTENT -(% OF BINDER)
AGGREGATE DESCRIPTION (GRADATION, MATERIAL TYPES, etc.):
Probably similar to datasheet #5 (9-10-90); however only local stone used; no qualified (select) material imported Top size: 18mm.
DISTRESS TYPE EXTENT OR FREOUENCY LOW MEDIUM HTGH
RUTTING 1 None 1
LONGITUDINAL CRACKING 1 None TRANSVERSE CRACKING 1 None I RAVELLING I x* I ALLIGATOR CRACKING 1 None I I BLOCK CRACKING 1 None I POTHOLES 1 None
* SEGREGATION
NARRATIVE DESCRIPTION OF PAVEMENT CONDITION:
Viewed northbound lanes. Pavement wet from earlier rain. Pavement showed irregular drying pattern caused by mix segregation. Pavement appeared very porous in randomly-spaced locations in between wheel paths. Wheel paths appeared normal, perhaps due to movement of mastic under traffic.
(form continued on reverse side)/26 JUNE 90 DRAINAGE FACILITIES:
COMMERCIAL SOURCE (IF PROPRIETARY FEATURE):
OTHER REMARKS:
POST-VISIT DEBRIEFING NOTES:
Pavement distress appeared to be ravelling. However, U.S. contractors on team agreed that distress resulted from mix segregation during construction.
APPLICABILITY TO U.S. PRACTICE:
COSTS RELATIVE TO CONVENTIONAL U.S. CONSTRUCTION PRACTICE:
35 mm PHOTOS: NO YES ROLL # NEGATIVE #‘S VIDEOTAPE: NO-YES- CASSETTE # AUDIOTAPE: NO-YES- CASSETTE #
REPORTER(S): FHWA/AASHTO/NAPA SITE VISIT REPORT DATE 9-10-90 #L
DESCRIPTION OF NOVEL PAVEMENT FEATURE:
SMA under construction (NCC Viacotop)
LOCATION (COUNTRY, LOCAL GOVERNMENT UNIT, HIGHWAY #, MILEPOST):
European Route E-6, just North of Bastad, Sweden
DATE OF CONSTRUCTION 9-10-90 LENGTH (mi/km) # OF LANES Divided 4-lane
ACTUAL ADT % TRUCKS EALs WHEN OPENED ACTUAL CURRENT DESIGNED
BRIEF DESCRIPTION OF PAVEMENT STRUCTURE (# OF LAYERS, LAYER THICKNESSES, etc):
38rnm thick (compacted) SMA overlay: 90 Viacotop 16.
ASPHALT CONTENT 6.7* (% OF MIX) AIR VOIDS CONTENT 3_(%)
MODIFIER TYPE Cellulose Pellets MODIFIER CONTENT 0.3(% OF MIX) (0.6% Fibers * Includes 0.3% from fiber pellets + Binder) AGGREGATE DESCRIPTION (GRADATION, MATERIAL TYPES, etc.):
Top size: 16mm; nominal gradation: 22% passing 2mm; 27% passing 4mm, 33% passing 8mm, 40% passing 12mm, 95% passing 16mm, 10% filler passing 0.075mm (#200 sieve).
DISTRESS TYPE EXTENT OR FREOUENCY LOW MEDIUM HIGH
RUTTING I I LONGITUDINAL CRACKING 1
TRANSVERSE CRACKING I I I I RAVELLING ALLIGATOR CRACKING I BLOCK CRACKING
POTHOLES
* SEGREGATION
NARRATIVE DESCRIPTION OF PAVEMENT CONDITION:
New; construction in progress. Asphalt cement grade: B85.
(form continued on reverse side)/26 JUNE 90 DRAINAGE FACILITIES:
COMMERCIAL SOURCE (IF PROPRIETARY FEATURE):
Viacotop is the tradename for SMA produced by NCC. This job employed pelletized cellulose fibers as a modifier.
OTHER REMARKS:
POST-VISIT DEBRIEFING NOTES:
The binder content is considerably higher for this project than for the Stabinor project reported in #5 (9- 10-90). However this mix is reported to hae good friction properties when newly laid.
Rolling was accomplished with two steel-wheeled rollers (10 metric tons each).
Pavement surface appeared rich in binder, almost to the point of flushing. However, the roller marks were much less pronounced than for the Stabinor mix. This mix appears much more stable.
APPLICABILITY TO U.S. PRACTICE:
COSTS RELATIVE TO CONVENTIONAL U.S. CONSTRUCTION PRACTICE:
35 mm PHOTOS: NO YES ROLL # NEGATIVE #‘S VIDEOTAPE: NO- YES- CASSETTE # AUDIOTAPE: NO- YES- CASSETTE #
REPORTER(S): FHWA/AASHTO/NAPA SITE VISIT REPORT DATE 9-11-90 #1 DESCRIPTION OF NOVEL PAVEMENT FEATURE:
Runway and Taxiway Rehabilitation Projects at Copenhagen Airport: a) EVA - Modified AC overlay on PCC (Accuplast Seal) b) Open graded A/C filled with superplasticized PCC (Densiphalt); c) Microfil- Modified AC overlay; d) Recycled 40 year old AC pavement.
LOCATION (COUNTRY, LOCAL GOVERNMENT UNIT, HIGHWAY #, MILEPOST):
Klastrup Airport, Copenhagen, Denmark
DATE OF CONSTRUCTION 9-11-90 LENGTH (mi/km) # OF LANES Divided 4-lane
ACTUAL ADT % TRUCKS EALs WHEN OPENED ACTUAL CURRENT N/A DESIGNED N/A BRIEF DESCRIPTION OF PAVEMENT STRUCTURE (# OF LAYERS, LAYER THICKNESSES, etc): c) Taxiway Reconstruction: Binder course and open-graded surface course. Binder course consists of HMA. Modified with carbon black (Microfil), hydrated lime (1.5% of mix) and cellulose fibers (0.25%)
ASPHALT CONTENTn(% OF MIX) AIR VOIDS CONTENT 4J%)
MODIFIER TYPE Micro”$1 MODIFIER CONT& 15- (% OF BINDER) AGGREGATE DESCRIPTION (GRADATION, MATERIAL TYPES, etc.): c) Top size: 20mm. Binder course employs conventional dense-graded aggregate.
DISTRESS TYPE EXTENT OR FREOUENCY LOW MEDIUM HIGH
RUTTING I LONGITUDINAL CRACKING 1
TRANSVERSE CRACKING
RAVELLING I ALLIGATOR CRACKING
BLOCK CRACKING
POTHOLES
NARRATIVE DESCRIPTION OF PAVEMENT CONDITION: a) EVA - Modified AC overlay: No visible distress. Another section developed rutting from heavy static tire loads.
(fom continued on reverse side)/26 JUNE. 90 DRAINAGE FACILITIES:
COMMERCIAL SOURCE (IF PROPRIETARY FEATURE):
Microfil is the tradename for a commercial carbon black product produced by Cabot Corporation.
OTHER REMARKS: c) Microfil-Modified AC overlay: SBS rubber and EVA polymer have also been tried as modifiers, but these present bitumen compatibility and separation problems. Also, SBS and EVA-modified pavements have failed under heavy static tire loads.
POST-VISIT DEBRIEFING NOTES: c) Microfil-Modified AC Overlay: The carbon black is employed to flatten the temperature susceptibility response of the 60 pm PDA-refined Danish bitumen. Carbon black apparently increases the compaction effort required to achieve satisfactory density The roller complement employed here was double that needed for unmodified HMA. Both steel- wheeled and pnuematic-tired rollers are used. The pneumatic-tired rollers are held off the pavement for 24 hours; this finish rolling is designed to improve durability. Compaction was intended to achieve 298% of Marshall density at 4% air voids.
Microfil appears to slow aging of HMA during production. It also flattens the response of Marshall stability and flow to changes in binder content. It has been employed with bitumens up to 120 pen. Cost in Denmark is about $1 per kg.
APPLICABILITY TO U.S. PRACTICE:
Uncertain.
COSTS RELATIVE TO CONVENTIONAL U.S. CONSTRUCTION PRACTICE:
Increased due to modifier cost and changes in construction practices.
35 mm PHOTOS: NO YES ROLL # NEGATIVE #‘S VIDEOTAPE: NO- YES CASSETTE # AUDIOTAPE: NO YES CASSETTE #
REPORTER(S) : FHWA/AASHTO/NAPA SITE VISIT REPORT DATE 9-11-90 #2 DESCRIPTION OF NOVEL PAVEMENT FEATURE:
SBS - Modified SMA overlay on a cracked and seated, 32-year old PCC pavement.
LOCATION (COUNTRY, LOCAL GOVERNMENT UNIT, HIGHWAY #, MILEPOST):
Helsingor Motorway (European Route E4) North from Copenhagen, Denmark
. DATE OF CONSTRUCTION 1988-90 LENGTH-&@i/km) # OF LANES Divided 4-lane
ACTUAL ADT % TRUCKS EALs WHEN OPENED ACTUAL CURRENT 40,000 5 DESIGNED N/A
BRIEF DESCRIPTION OF PAVEMENT STRUCTURE (# OF LAYERS, LAYER THICKNESSES, etc):
40 mm SMA over 60mm HMA binder course over either cracked and seated PCC slabs or 100 mm HMA base course where poor PCC was replaced.
ASPHALT CONTENTm(% OF MIX) AIR VOIDS CONTENT -(%)
MODIFIER TYPE SBS/Cellulose Fibers SBS CONTENT 6 (% OF BINDER) FIBER CONTENT 0.25(% OF MIX) AGGREGATE DESCRIPTION (GRADATION, MATERIAL TYPES, etc.):
82% crushed rock, 15% luxovit (burned flint, light stones), 2.75% filler, 0.25% fibers. Nominal gradation: 22% passing 2mm; 28% passing 4mm, 53% passing 8mm, 93% passing 11.2mm, 100% passing 16mm, 7.2% jiller passing 0.075mm (#200 sieve).
DISTRESS TYPE EXTENT OR FREOUENCY LOW MEDIUM HIGH
RUTTING 1 Slight I I I
LONGITUDINAL CRACKING 1 None I I I
TRANSVERSE CRACKING 1 None I II RAVELLING 1 None ALLIGATOR CRACKING 1 None I I I BLOCK CRACKING 1 None I I I POTHOLES 1 None I I I
NARRATIVE DESCRIPTION OF PAVEMENT CONDITION:
Slight flushed appearance in wheel tracks of driving lane. Passing lane has very even appearance.
(form continued on reverse side)/26 JUNE 90 DRAINAGE FACILITIES:
COMMERCIAL SOURCE (IF PROPRIETARY FEATURE):
OTHER REMARKS:
Binder course is 50% recycled HMA.
Cellulose fibers cost 10 kr/kg ($0.65/lb).
SMA binder is modified with SBS to increase flexibility.
POST-VISIT DEBRIEFING NOTES:
APPLICABILITY TO U.S. PRACTICE:
High.
COSTS RELATIVE TO CONVENTIONAL U.S. CONSTRUCTION PRACTICE:
First costs increased by addition of cellulose fibers and SBS.
35 mm PHOTOS: NO YES ROLL # NEGATIVE #‘S VIDEOTAPE: NO-YES- CASSETTE # AUDIOTAPE: NO-YES- CASSETTE #
REPORTER(S): FHWA/AASHTO/NAPA SITE VISIT REPORT DATE 9-12-90 #2
DESCRIPTION OF NOVEL PAVEMENT FEATURE:
SMA Surface Course on a heavily trafjiced urban street.
LOCATION (COUNTRY, LOCAL GOVERNMENT UNIT, HIGHWAY #, MILEPOST):
Barmbekerstrasse, Hamburg, Germany
DATE OF CONSTRUCTION 1984 LENGTH-(mi/km) # OF LANES 4 (undivided)
ACTUAL ADT % TRUCKS EALs WHEN OPENED ACTUAL CURRENT 40,000 6 DESIGNED
BRIEF DESCRIPTION OF PAVEMENT STRUCTURE (# OF LAYERS, LAYER THICKNESSES, etc):
40 mm SMA over 40mm HMA binder course over 140mm asphalt base course over 520mm of treated base material on frost-proof sand. This pavement section is intended for intermediate traffic loads.
ASPHALT CONTENT-(% OF MIX) AIR VOIDS CONTENT -(%)
MODIFIER TYPE Cellulose Fibers MODIFIER CONTENT (% OF MIX)
AGGREGATE DESCRIPTION (GRADATION, MATERIAL TYPES, etc.):
Top size: 11mm.. 70 to 80% of aggregate is crushed material. Remainder consists of manufactured and natural sands and filler. Nominal gradation: 90-100% passing 11.2mm, 50- 75% passing 8mm, 30-50% passing 5mm, 20-30% passing 2mm and 8-13% passing 0.09mm.
DISTRESS TYPE EXTENT OR FREOUENCY LOW MEDIUM HIGH
RUTTING 1 None
LONGITUDINAL CRACKING 1 None
TRANSVERSE CRACKING 1 None
RAVELLING 1 None
ALLIGATOR CRACKING 1 None
BLOCK CRACKING 1 None
POTHOLES 1 None
NARRATIVE DESCRIPTION OF PAVEMENT CONDITION:
As noted, no distress is apparent of a significant nature. Hamburg roads and streets agency personnel indicated that typical service life for SMA in these circumstances is 10 years.
(form continued on reverse side)/26 JUNE 90 DRAINAGE FACILITIES:
COMMERCIAL SOURCE (IF PROPRIETARY FEATURE):
OTHER REMARKS:
POST-VISIT DEBRIEFING NOTES:
APPLICABILITY TO U.S. PRACTICE:
High.
COSTS RELATIVE TO CONVENTIONAL U.S. CONSTRUCTION PRACTICE:
In Germany, SMA costs about 20 percent more than conventional HMA.
35 mm PHOTOS: NO YES ROLL # NEGATIVE #‘S VIDEOTAPE: NO- YES- CASSETTE # AUDIOTAPE: NO- YES- CASSETTE #
REPORTER(S): FH.WA/AASHTO/NAPA SITE VISIT REPORT DATE 9-12-90 #3 DESCRIPTION OF NOVEL PAVEMENT FEATURE:
Gussasphalt Surface Course on a heavily trafficed urban street.
LOCATION (COUNTRY, LOCAL GOVERNMENT UNIT, HIGHWAY #, MILEPOST):
Behringstrasse, Hamburg, Germany
DATE OF CONSTRUCTION 1973 LENGTH-(rni/km) # OF LANES 4 (undivided)
ACTUAL ADT % TRUCKS EALs WHEN OPENED 40,000 ACTUAL CURRENT 40,000 6 DESIGNED BRIEF DESCRIPTION OF PAVEMENT STRUCTURE (# OF LAYERS, LAYER THICKNESSES, etc):
40 mm Gussasphalt over 80mm HMA binder course Er 160mm HMA over 400mm of treated base material on frost-proof sand. This pavement section is intended for the highest traffic loads.
ASPHALT CONTENT7-8 (% OF MIX) AIR VOIDS CONTENT &(%)
MODIFIER TYPE _ MODIFIER CONTENT (% OF MIX)
AGGREGATE DESCRIPTION (GRADATION, MATERIAL TYPES, etc.):
Top size: 12mm. Nominal gradation: 90 to 100% passing 11.2mm, 70-80% passing 8mm, 45-55% passing 2mm and 20-30% passing 0.09mm. Aggregate consists of crushed stone, manufactured or natural sand and filler.
DISTRESS TYPE EXTENT OR FREOUENCY LOW MEDIUM HIGH
RUTTING 1 None to 1
LONGITUDINAL CRACmmne-w TRANSVERSE CRACKING 1 None
RAVELLING 1 None
ALLIGATOR CRACKING 1 None
BLOCK CRACKING 1 None
POTHOLES 1 None
NARRATIVE DESCRIPTION OF PAVEMENT CONDITION:
Excellent considering its long service life. Gussaphalt typically yields a service life of 1.5 years or more compared to 12 years for SMA.
(form continued on reverse side)/26 JUNE 90 DRAINAGE FACILITIES:
COMMERCIAL SOURCE (IF PROPRIETARY FEATURE):
OTHER REMARKS:
Gussasphalt is a pourable HMA that is placed at ,TO@‘C (575°F) with a special screed. It can also be poured from buckets and "floated" with hand tools similar to PCC. No compaction is required. It is covered with excess chipping at a rate of 1.5 kg/m2 which are rolled in with a very heavy roller.
POST-VISIT DEBRIEFING NOTES:
APPLICABILITY TO U.S. PRACTICE:
Low. Its use probably would be prohibited almost every where due to air pollution regulations. High.
COSTS RELATIVE TO CONVENTIONAL U.S. CONSTRUCTION PRACTICE:
In Germany, Gussaphalt costs almost two times as much as conventional HMA.
35 mm PHOTOS: NO YES ROLL # NEGATIVE #‘S VIDEOTAPE: NO YES- CASSETTE # AUDIOTAPE: NO- YES- CASSETTE #
REPORTER(S): FHWA/AASHTO/NAPA SITE VISIT REPORT DATE 9-12-90 #A
DESCRIPTION OF NOVEL PAVEMENT FEATURE:
Gussasphalt Surface Course LOCATION (COUNTRY, LOCAL GOVERNMENT UNIT, HIGHWAY #, MILEPOST):
Autobahn A-7, North of Kassel, Lower Saxony, Germany
DATE OF CONSTRUCTION 5-1990 LENGTH-(mi/km) # OF LANES 4 (divided)
ACTUAL ADT % TRUCKS EALS WHEN OPENED 50,000 17-20 ACTUAL CURRENT 50,000 (mean) 17-20 DESIGNED 80,000 (maximum)
BRIEF DESCRIPTION OF PAVEMENT STRUCTURE (# OF LAYERS, LAYER THICKNESSES, etc):
40 mm Gussasphalt Surface Course over 80mm HMA Binder course over 180mm asphalt base course.
ASPHALT CONTENTd(% OF MIX) AIR VOIDS CONTENT OJ%)
MODIFIER TYPE Trinidad Lake Asphalt MODIFIER CONTENT 2 (% OF MIX)
AGGREGATE DESCRIPTION (GRADATION, MATERIAL TYPES, etc.):
Top size: llmm. Nominal Gradation: 90 to 100% passing 11.2mm, 70-85% passing 8mm, 45-55% passing 2mm, and 20-30% passing 0.09mm. Aggregate consists of crushed stone, manufactured and natural sand, and mineral filler.
DISTRESS TYPE EXTENT OR FREOUENCY LOW MEDIUM HIGH
RUTTING 1 None I LONGITUDINAL CRACI 1 TRANSVERSE CRACKING 1 None
RAVELLING 1 None
ALLIGATOR CRACKING 1 None
BLOCK CRACKING 1 None
POTHOLES 1 None
NARRATIVE DESCRIPTION OF PAVEMENT CONDITION:
Surface appeared rough, but this is normal due to the rolled-in chippings. Wheel paths have a smoother overall appearance. There were isolated paths that appeared to be ravelled, but may be related to the rolled-in chippings.
(form continued on reverse side)/26 JUNE 90 DRAINAGE FACILITIES:
COMMERCIAL SOURCE (IF PROPRIETARY FEATURE):
OTHER REMARKS:
Gussasphalt is a pour-able HMA that is placed at 300°C (575°F) with a special screed. It can also be poured from buckets and "floated" with hand tools in a manner similar to PCC. No compaction is required. It is covered with excess chipping at a rate of 15 kg/m’, these are rolled into the surface with a very heavy roller.
POST-VISIT DEBRIEFING NOTES:
APPLICABILITY TO U.S. PRACTICE:
Low due to environmental problems.
COSTS RELATIVE TO CONVENTIONAL U.S. CONSTRUCTION PRACTICE:
In Germany, Gussaphalt costs almost two times as much as conventional HMA.
35 mm PHOTOS: NO YES ROLL # NEGATIVE #‘S VIDEOTAPE: NO YES CASSETTE # AUDIOTAPE: NO YES- CASSETTE #
REPORTER(S): FHWA/AASHTO/NAPA SITE VISIT REPORT DATE 9-13-90 #1
DESCRIPTION OF NOVEL PAVEMENT FEATURE:
Ralumac Slurry Seal LOCATION (COUNTRY, LOCAL GOVERNMENT UNIT, HIGHWAY #, MILEPOST):
Highway P38 westbound between Autobahn A-65 and Neustadt and der Weinstrasse, Rheinland - Pfalz, Germany.
DATE OF CONSTRUCTION 9-13-90 LENGTH-(mi/km) # OF LANESA
ACTUAL ADT % TRUCKS EALs WHEN OPENED ACTUAL CURRENT 12,500 DESIGNED
BRIEF DESCRIPTION OF PAVEMENT STRUCTURE (# OF LAYERS, LAYER THICKNESSES, etc):
Ralumac slurry seal (Microsurfacing) applied at a nominal thickness of 8mm to fill existing ruts in pavement and provide a level surface.
ASPHALT CONTENTN/A (% OF MIX) AIR VOIDS CONTENT y/A (%)
MODIFIER TYPE Latex rubber/emulsifier MODIFIER CONTENT (% OF MIXi
AGGREGATE DESCRIPTION (GRADATION, MATERIAL TYPES, etc.): Top size: 5mm. 8mm top size has been used on east-bound lane surfaced earlier in day.
DISTRESS TYPE EXTENT OR FREOUENCY LOW MEDIUM HIGH
RUTTING 1 N/A
LONGITUDINAL CRACtimxx
TRANSVERSE CRACKING I WA RAVELLING 1 N/A
ALLIGATOR CRACKING 1 N/A
BLOCK CRACKING 1 N/A POTHOLES I N/A
NARRATIVE DESCRIPTION OF PAVEMENT CONDITION:
The existing pavement had been deeply rutted. A first layer of Ralumac was applied to fill the ruts. Then a second complete layer 8mm thick was applied. Traffic was permitted onto surface also immediately; however, it typically takes several days for all the water in the emulsion to evaporate. Ralumac is considered to have more structural value than other slurry seals. A useable service life of 2-3 years is expected for this Microsurfacing.
(form continued on reverse side)/26 JUNE 90 DRAINAGE FACILITIES:
COMMERCIAL SOURCE (IF PROPRIETARY FEATURE):
Ralumac is a proprietary product of Raschig AC, Ludwigshafen, Germany.
OTHER REMARKS:
POST-VISIT DEBRIEFING NOTES:
APPLICABILITY TO U.S. PRACTICE:
This product is widely used in US.
COSTS RELATIVE TO CONVENTIONAL U.S. CONSTRUCTION PRACTICE:
35 mm PHOTOS: NO YES ROLL # NEGATIVE #‘S VIDEOTAPE: NO YES- CASSETTE # AUDIOTAPE: NO-YES CASSETTE #
REPORTER(S): FHWA/AASHTO/NAPA SITE VISIT REPORT DATE 9-13-90 #A
DESCRIPTION OF NOVEL PAVEMENT FEATURE:
Reconstruction of a rutted pavement with SMA surface course. (At time of visit, asphalt base course was being laid).
LOCATION (COUNTRY, LOCAL GOVERNMENT UNIT, HIGHWAY #, MILEPOST):
Autobahn A-65 (Northbound), North of Neustadt an der Weinstrasse Interchange, near KP 117,100, Rheinland - Pfal., Germany.
DATE OF CONSTRUCTION 9-13-90 LENGTH-(n-d/km) # OF LANES 4 (divided)
ACTUAL ADT % TRUCKS EALs WHEN OPENED ACTUAL CURRENT DESIGNED
BRIEF DESCRIPTION OF PAVEMENT STRUCTURE (# OF LAYERS, LAYER THICKNESSES, etc): Driving (Right-Hand) Lane: 35mm SMA over stress-absorbing membrane interlayer over 80 mm HMA binder course over 100 mm asphalt base course over 200 mm cement-treated base.
ASPHALT CONTENT Z.5* (% OF MIX) AIR VOIDS CONTENT 3x(%)
MODIFIER TYPE Cellulose fibers MODIFIER CONTENT 0.3* (% OF MIX) * Nominal AGGREGATE DESCRIPTION (GRADATION, MATERIAL TYPES, etc.): Top size: 11 mm. TYPICAL GRADATION: 90-100% Passing 11.2mm, 50-75% passing 8mm, 30-50% passing 5mm, 20-30% passing 2mm and 8-13% filler passing 0/09mm. Crushed rock or stone composes 75% of aggregate, natural and manufactured sand 15% and mineral filler 10%.
DISTRESS TYPE EXTENT OR FREOUENCY LOW MEDIUM HIGH
RUTTING I WA LONGITUDINAL CRACr
TRANSVERSE CRACKING I N/A
RAVELLING I WA
ALLIGATOR CRACKING I WA BLOCK CRACKING 1 N/A
POTHOLES 1 N/A
NARRATIVE DESCRIPTION OF PAVEMENT CONDITION: Rutting had occurred in driving lane of original pavement. This lane was milled out to a depth of 38cm and reconstructed with the pavement section described above. SMA and SAM will extend across entire pavement width. This type of reconstruction was necessitated by the fact that substantial overlays would have blocked the existing drainage system.
(form continued on reverse side)/26 JUNE 90 DRAINAGE FACILITIES:
COMMERCIAL SOURCE (IF PROPRIETARY FEATURE):
OTHER REMARKS:
POST-VISIT DEBRIEFING NOTES:
APPLICABILITY TO U.S. PRACTICE:
COSTS RELATIVE TO CONVENTIONAL U.S. CONSTRUCTION PRACTICE:
35 mm PHOTOS: NO YES ROLL # NEGATIVE #‘S VIDEOTAPE: NO-YES- CASSETTE # AUDIOTAPE: NO-YES- CASSETTE #
REPORTER(S): FHWA/AASHTO/NAPA SITE VISIT REPORT DATE 9-14-90 #.J-.
DESCRIPTION OF NOVEL PAVEMENT FEATURE:
Danasphalt (Porous Asphalt) overlay on pavement and shoulders
LOCATION (COUNTRY, LOCAL GOVERNMENT UNIT, HIGHWAY #, MILEPOST):
Autobahn A-6, east of Heilbronn, Baden - Wurttemberg, Germany.
DATE OF CONSTRUCTION _ LENGTH-(mi/km) # OF LANES-
ACTUAL ALIT % TRUCKS EALs WHEN OPENED ACTUAL CURRENT DESIGNED
BRIEF DESCRIPTION OF PAVEMENT STRUCTURE (# OF LAYERS, LAYER THICKNESSES, etc):
ASPHALT CONTENT5.0 (% OF MIX) AIR VOIDS CONTENT B( %) (Marshall Design) Polymer-modified MODIFIER TYPE emulsion and 0.5% MODIFIER CONTENT (% OF MIX) cellulose fibers AGGREGATE DESCRIPTION (GRADATION, MATERIAL TYPES, etc.): Top size: 8 and 11 mmin different sections. Nominal gradation: 85% retained on 2mm, 5% filler passing 0.09 mm. Binder is polymer-modified cationic emulsion of a B65 - grade bitumen. Cellulose fibers are added to reduce drainage during construction.
DISTRESS TYPE EXTENT OR FREOUENCY LOW MEDIUM HIGH
RUTTING 1 None
LONGITUDINAL CRACamFe I I
TRANSVERSE CRACKING 1 None I RAVELLING 1 None ALLIGATOR CRACKING 1 None I I BLOCK CRACKING 1 None POTHOLES 1 None I I I
NARRATIVE DESCRIPTION OF PAVEMENT CONDITION: Viewed several sections of porous asphalt overlays intended to reduce hydroplaning and traffic noise.
(form continued on reverse side)/26 JUNE 9U DRAINAGE FACILITIES:
COMMERCIAL SOURCE (IF PROPRIETARY FEATURE):
OTHER REMARKS: Porous asphalt surface courses on main lines are self-cleaning due to the action of high-speed traffic.
POST-VISIT DEBRIEFING NOTES:
No standard mix design has been established yet for porous asphalt by the German road authorities. Riding surface is very quiet.
APPLICABILITY TO U.S. PRACTICE:
Uncertain. Use of impermeable seal layer under porous asphalt might eliminate some of the problems experienced in the U.S. with open-graded asphalt courses.
COSTS RELATIVE TO CONVENTIONAL U.S. CONSTRUCTION PRACTICE: In Germany, porous asphalt costs 100% more than conventional HMA.
35 mm PHOTOS: NO YES ROLL # NEGATIVE #‘S VIDEOTAPE: NO- YES- CASSETTE # AUDIOTAPE: NO- YES- CASSETTE #
REPORTER(S): FHWA/AASHTO/NAPA SITE VISIT REPORT DATE 9-14-90 #2
DESCRIPTION OF NOVEL PAVEMENT FEATURE:
Surface course on reconstructed pavement, including bridge decks. Dranasphalt (Porous Asphalt).
LOCATION (COUNTRY, LOCAL GOVERNMENT UNIT, HIGHWAY #, MILEPOST):
Autobahn A-81, south of Heilbronn, Baden - Wurttemberg, Germany, near KP 561.0.
DATE OF CONSTRUCTION 9-14-90 LENGTH-(mi/km) # OF LANES-
ACTUAL ADT % TRUCKS EALs WHEN OPENED ACTUAL CURRENT 90,000 33 DESIGNED BRIEF DESCRIPTION OF PAVEMENT STRUCTURE (# OF LAYERS, LAYER THICKNESSES, etc): 35mm Dranasphalt over 40mm (seal layer prepared with polymer-modified asphalt emulsion over existing pavement milled-out pavement. ASPHALT CONTENT5.0 (% OF MIX) AIR VOIDS CONTENT ,Is( %) (Marshall Design) Polymer-modified MODIFIER TYPE emulsion and 0.5% MODIFIER CONTENT (% OF MIX) cellulose fibers AGGREGATE DESCRIPTION (GRADATION, MATERIAL TYPES, etc.): Top size: 11 mm. Nominal gradation: 8.5% retained on 2mm, 5% filler passing 0.09 mm. Binder is polymer-modified cationic emulsion of a B65 - grade bitumen. Cellulose fibers are added to reduce drainage during construction.
DISTRESS TYPE EXTENT OR FREOUENCY LOW MEDIUM HIGH
RUTTING I I LONGITUDINAL CRACmr-j
TRANSVERSE CRACKING
RAVELLING
ALLIGATOR CRACKING I BLOCK CRACKING
POTHOLES
NARRATIVE DESCRIPTION OF PAVEMENT CONDITION: Reconstruction of rutted pavement subjected to very high traffic volume and channelized truck traffic.
(form continued on reverse side)/26 JUNE 90 DRAINAGE FACILITIES:
Box drains installed 40 mm into the binder course, extending through the seal layer to contact the porous asphalt.
COMMERCIAL SOURCE (IF PROPRIETARY FEATURE):
OTHER REMARKS: Group witnessed construction of asphalt binder course. Three rollers follow closely upon paver. Two pneumatic-tired rollers provide breakdown, followed by a single steel-wheeled roller. Porous asphalt is also compacted with normal rollers without vibration.
POST-VISIT DEBRIEFING NOTES:
No standard mix design has been established yet for porous asphalt by the German road authorities. This project involves the reconstruction of an existing pavement structure. Existing pavement is milled out, one lane at a time, to a depth of 70mm. A new 70 mm polymer-modified asphalt emulsion seal layer and a 35mm porous asphalt surface course. The seal layer is designed to prevent the intrusion of water into the pavement structure underlying the porous asphalt. The seal layer and the porous asphalt extend across the pavement and the shoulders; it consists of polymer-modified cationic asphalt emulsion, applied at 2 kg/m’, dressed with chippings applied at 8 to 10 kg/m2.
APPLICABILITY TO U.S. PRACTICE:
Uncertain. Use of impermeable seal layer under porous asphalt might eliminate some of the problems experienced in the U.S. with open-graded asphalt courses.
COSTS RELATIVE, TO CONVENTIONAL U.S. CONSTRUCTION PRACTICE: In Germany, porous asphalt costs 100% more than conventional HMA.
35 mm PHOTOS: NO YES ROLL # NEGATIVE #‘S VIDEOTAPE: NO- YES CASSETTE # AUDIOTAPE: NO- YES- CASSETTE #
REPORTER(S): FHWA/AASHTO/NAPA SITE VISIT REPORT DATE 9-14-90 #3
DESCRIPTION OF NOVEL PAVEMENT FEATURE:
Dranasphalt (Porous Asphalt) Surface Course.
LOCATION (COUNTRY, LOCAL GOVERNMENT UNIT, HIGHWAY #, MILEPOST):
Autobahn A-81 northbound, near Freiberg in Breisgan, Baden - Wurttembetg, Germany, near KP 561.0.
DATE OF CONSTRUCTION 1990 LENGTH-(mi/km) # OF LANES 6 (divided)
ACTUAL ADT % TRUCKS EALs WHEN OPENED ACTUAL CURRENT 90,000 33 DESIGNED BRIEF DESCRIPTION OF PAVEMENT STRUCTURE (# OF LAYERS, LAYER THICKNESSES, etc): 35mm Dranasphalt over 40mm seal layer over 70 mm asphalt binder course.
ASPHALT CONTENT5.0 (% OF MIX) AIR VOIDS CONTENT ZJ( %) (Marshall Design) Polymer-modified B65 MODIFIER TYPE Bitumen in Cationic emulsion MODIFIER CONTENT (% OF MIX) cellulose fibers AGGREGATE DESCRIPTION (GRADATION, MATERIAL TYPES, etc.): Top size: 11 mm. Nominal gradation: 85% retained on 2mm, 5% filler passing 0.09 mm. Binder is polymer-modified B65 bitumen in cationic emulsion. Cellulose fibers are added to reduce drainage during construction.
DISTRESS TYPE EXTENT OR FREOUENCY LOW MEDIUM HIGH
RUTTING 1 None
LONGITUDINAL CRACU!; I I TRANSVERSE CRACKING 1 None
RAVELLING 1 None
ALLIGATOR CRACKING 1 None
BLOCK CRACKING 1 None
POTHOLES 1 None
NARRATIVE DESCRIPTION OF PAVEMENT CONDITION: No apparent distress. Pavement is very quiet.
(form continued on reverse side)/26 JUNE 90 DRAINAGE FACILITIES:
COMMERCIAL SOURCE (IF PROPRIETARY FEATURE):
OTHER REMARKS:
POST-VISIT DEBRIEFING NOTES:
No standard mix design has been established yet for porous asphalt by the German road authorities, Impermeable seal layer is always applied under porous asphalt. The layer is nominally 40mm thick It is composed of a polymer-modified B65 bitumen cationic emulsion applied at 2 kg/m2 and dressed with stone chipping applied at 8 to IO kg/m2.
APPLICABILITY TO U.S. PRACTICE:
Uncertain Use of impermeable seal layer under porous asphalt might eliminate some of the problems experienced in the U.S. with open-graded asphalt courses.
COSTS RELATIVE TO CONVENTIONAL U.S. CONSTRUCTION PRACTICE: In Germany, porous asphalt costs 100% more than conventional HMA.
35 mm PHOTOS: NO YES ROLL # NEGATIVE #‘S VIDEOTAPE: NO- YES- CASSETTE # AUDIOTAPE: NO- YES- CASSETTE #
REPORTER(S): FHWA/AASHTO/NAPA SITE VISIT REPORT DATE 9-14-90 #3
DESCRIPTION OF NOVEL PAVEMENT FEATURE:
Dranasphalt (Porous Asphalt) Surface Course.
LOCATION (COUNTRY, LOCAL GOVERNMENT UNIT, HIGHWAY #, MILEPOST):
Autobahn A-81 northbound, near Freiberg in Breisgan, Baden - Wurttemberg, Germany, near KP 561.0.
DATE OF CONSTRUCTION 1990 LENGTH-(mi/km) # OF LANES 6 (divided)
ACTUAL ADT % TRUCKS EALs WHEN OPENED ACTUAL CURRENT 90,000 33 DESIGNED BRIEF DESCRIPTION OF PAVEMENT STRUCTURE (# OF LAYERS, LAYER THICKNESSES, etc): 35mm Dranasphalt over 40mm seal layer over 70 mm asphalt binder course.
ASPHALT CONTENTAIR5.0 (%VOIDS OF MIX) CONTENT u(%) (Marshall Design) Polymer-modified B65 MODIFIER TYPE Bitumen in Cationic emulsion MODIFIER CONTENT (% OF MIX) cellulose fibers AGGREGATE DESCRIPTION (GRADATION, MATERIAL TYPES, etc.): Top size: 11 mm. Nominal gradation: 85% retained on 2mm, 5% filler passing 0.09 mm. Binder is polymer-modified B65 bitumen in cationic emulsion Cellulose fibers are added to reduce drainage during construction
DISTRESS TYPE EXTENT OR FREOUENCY LOW MEDIUM HIGH
RUTTING 1 None I
LONGITUDINAL CRACK?!; I I TRANSVERSE CRACKING I None II RAVELLING IN one ALLIGATOR CRACKING 1 None
BLOCK CRACKING 1 None POTHOLES 1 None I I
NARRATIVE DESCRIPTION OF PAVEMENT CONDITION: No apparent distress. Pavement is very quiet.
(form continued on reverse side)/26 JUNE 90 DRAINAGE FACILITIES:
COMMERCIAL SOURCE (IF PROPRIETARY FEATURE):
OTHER REMARKS:
POST-VISIT DEBRIEFING NOTES:
No standard mix design has been established yet for porous asphalt by the German road authorities. Impermeable seal layer is always applied under porous asphalt. The layer is nominally 40mm thick. It is composed of a polymer-modified B65 bitumen cationic emulsion applied at 2 kg/m2 and dressed with stone chipping applied at 8 to 10 kg/m2.
APPLICABILITY TO U.S. PRACTICE:
Uncertain. Use of impermeable seal layer under porous asphalt might eliminate some of the problems experienced in the U.S. with open-graded asphalt courses.
COSTS RELATIVE TO CONVENTIONAL U.S. CONSTRUCTION PRACTICE: In Germany, porous asphalt costs 100% more than conventional HMA.
35 mm PHOTOS: NO YES ROLL # NEGATIVE #‘S VIDEOTAPE: NO- YES- CASSETI’E # AUDIOTAPE: NO- YES- CASSETTE #
REPORTER(S): FHWA/AASHTO/NAPA SITE VISIT REPORT DATE 9-20-90 #1
DESCRIPTION OF NOVEL PAVEMENT FEATURE:
Reconstruction of the MI motorway to strengthen pavement and extend its service life (original construction: 1968).
LOCATION (COUNTRY, LOCAL GOVERNMENT UNIT, HIGHWAY #, MILEPOST): Motorway Ml southbound, near junction 27, north of Nottingham, Nottinghamshire, United Kingdom.
DATE OF CONSTRUCTION 1990 LENGTH-(mi/km) # OF LANES 6 (divided)
ACTUAL ADT % TRUCKS EALs WHEN OPENED ACTUAL CURRENT 90,000 33 DESIGNED
BRIEF DESCRIPTION OF PAVEMENT STRUCTURE (# OF LAYERS, LAYER THICKNESSES, etc): 35mm Dranasphalt over 40mm seal layer over 70 mm asphalt binder course. ASPHALT CONTENTu(% OF MIX) AIR VOIDS CONTENT B(%) (Marshall Design) Polymer-modified B65 MODIFIER TYPE Bitumen in Cationic emulsion MODIFIER CONTENT (% OF MIX) cellulose fibers AGGREGATE DESCRIPTION (GRADATION, MATERIAL TYPES, etc.): Top size: II mm. Nominal gradation: 85% retained on 2mm, 5% filler passing 0.09 mm. Binder is polymer-modified B65 bitumen in cationic emulsion. Cellulose fibers are added to reduce drainage during construction.
DISTRESS TYPE EXTENT OR FREOUENCY LOW MEDIUM HIGH
RUTTING 1 None
LONGITUDINAL CRACU-T I
TRANSVERSE CRACKING 1 None .I RAVELLING INone II ALLIGATOR CRACKING 1 None I BLOCK CRACKING 1 None POTHOLES 1 None I
NARRATIVE DESCRIPTION OF PAVEMENT CONDITION: No apparent distress. Pavement is very quiet.
(form continued on reverse side)/26 JUNE 90 DRAINAGE FACILITIES:
COMMERCIAL SOURCE (IF PROPRIETARY FEATURE):
OTHER REMARKS:
POST-VISIT DEBRIEFING NOTES:
No standard mix design has been established yet for porous asphalt by the German road authorities. Impermeable seal layer is always applied under porous asphalt. The layer is nominally 40mm thick. It is composed of a polymer-modi’ed B65 bitumen cationic emulsion applied at 2 kg/in’ and dressed with stone chipping applied at 8 to 10 kg/m2.
APPLICABILITY TO U.S. PRACTICE:
Uncertain. Use of impermeable seal layer under porous asphalt might eliminate some of the problems experienced in the U.S. with open-graded asphalt courses.
COSTS RELATIVE TO CONVENTIONAL U.S. CONSTRUCTION PRACTICE: In Germany, porous asphalt costs 100% more than conventional HMA.
35 mm PHOTOS: NO YES ROLL # NEGATIVE #‘S VIDEOTAPE: NO- YES CASSETTE # AUDIOTAPE: NO- YES CASSETTE # REPORTER(S): FHWA/AASHTO/NAPA SITE VISIT REPORT DATE 9-20-90 #I
DESCRIPTION OF NOVEL PAVEMENT FEATURE:
Reconstruction of the Ml motorway to strengthen pavement and extend its service life (original construction: 1968). LOCATION (COUNTRY, LOCAL GOVERNMENT UNIT, HIGHWAY #, MILEPOST):
Motorway MI southbound, near junction 27, north of Nottingham, Nottinghamshire, United Kingdom.
DATE OF CONSTRUCTION 9-20-90 LENGTH --(mi/km)9 # OF LANES 6 (Divided)
ACTUAL ADT % TRUCKS EALs WHEN OPENED ACTUAL CURRENT 60,650 25 DESIGNED
BRIEF DESCRIPTION OF PAVEMENT STRUCTURE (# OF LAYERS, LAYER THICKNESSES, etc): Maximum reconstruction taking place in inner (slow) lane; center and outer lanes are receiving lesser reconstruction. Inner lane pavement structure: 40mm hot-rolled asphalt (HRA) wearing course Er 215mm heavy duty bitumen macadam upper road base over 125 mm HRA lower road base.
ASPHALT CONTENT_T_(% OF MIX) AIR VOIDS CONTENT _T_(%)
MODIFIER TYPE _2_ MODIFIER CONTENT “(% OF MIX)
AGGREGATE DESCRIPTION (GRADATION, MATERIAL TYPES, etc.): *
DISTRESS TYPE EXTENT OR FREOUENCY LOW MEDIUM HIGH RUTTING I I I I LONGITUDINAL CRACKING 1 I TRANSVERSE CRACKING
RAVELLING ALLIGATOR CRACKING I I I I BLOCK CRACKING I POTHOLES I I I I
NARRATIVE DESCRIPTION OF PAVEMENT CONDITION: Original pavement in northbound lanes shows little apparent distress. Motorway was built in 1968 and overlaid in 1981 with a 40 mm HRA wearing course. Decision to reconstruct was based upon deflection measurements. It was noted that the condition of the northbound lanes would require less reconstruction than witnessed for the southbound lanes.
* See reverse and attached sheet. (form continued on reverse side)/26 JUNE 90 DRAINAGE FACILITIES: Filter drains on verges (shoulders) and medians. These are being excavated and replaced with fresh limestone chippings.
COMMERCIAL SOURCE (IF PROPRIETARY FEATURE):
None
OTHER REMARKS: 1. Lanes milled out to required depths with a cold planer: 30mm on inner lane, 100mm on center lane, none on outer lane. 2. The old laydown of upperoad base on inner lane. Pavers have fixed screeds. Two pavers lay about 5,500 tons of mix per day. Laydown accomplished at 160°C. (continued on attachment) POST-VISIT DEBRIEFING NOTES: Details of Reconstruction: INNER (#1) LANE CENTER (#2) LANE OUTER (#3) LANE ___----I- T ------.------Wearing 4omm 30% 40mm 30% 40MM 30% Course Hot-rolled Hot-rolled Hot-rolled (1 W- Asphalt Asphalt Asphalt service life) ---- Upper road 115mm + 100mm 60mm 60% 60mm 60% Hot base Heavy duty Hot-rolled rolled Asphalt (resists bitumen macadam asphalt base course base course rutting) ______------(Existing Surface) --- Lower road 125mm 60% base Hot-rolled EXISTING PAVEMENT STR UCTURE (resists Asphalt tensile stresses) ------Subgrade/ #100mm dense-graded Macadam over $200 to 300mm continuously graded Subbase limestone on a stiff marl.
APPLICABILITY TO U.S. PRACTICE: Uncertain. This pavement structure should be compared to usual U.S. designs for similar cirumstances, to determine if equal or improved pavement service can be achieved at comparable costs.
COSTS RELATIVE TO CONVENTIONAL U.S. CONSTRUCTION PRACTICE:
Total project cost about $8,000,000 for reconstruction of 9 km (5.4 miles) of 6-lane pavement. This works our roughly to an average of $34.25 per square yard.
35 mm PHOTOS: NO YES ROLL # NEGATIVE #‘S VIDEOTAPE: NO- YES- CASSETTE # AUDIOTAPE: NO- YES- CASSETTE #
REPORTER(S): FHWA/AASHTO/NAPA SITE VISIT REPORT DATE 9-17-90 #I
DESCRIPTION OF NOVEL PAVEMENT FEATURE:
Ultrathin Asphalt Wearing Course.
LOCATION (COUNTRY, LOCAL GOVERNMENT UNIT, HIGHWAY #, MILEPOST):
RD 68 between Ste-lute and Thouare, Loire Atlantique, France
DATE OF CONSTRUCTION 7-90 LENGTH --(mi/km) # OF LANES2 ACTUAL ADT % TRUCKS EALs WHEN OPENED ACTUAL CURRENT Low DESIGNED
BRIEF DESCRIPTION OF PAVEMENT STRUCTURE (# OF LAYERS, LAYER THICKNESSES, etc): 15 mm overlay laid with conventional paver.
ASPHALT CONTENTJ&(% OF MIX) AIR VOIDS CONTENT fi(%)
MODIFIER TYPE SBS Latex NOMINAL CONTENT J(% OF BINDER)
AGGREGATE DESCRIPTION (GRADATION, MATERIAL TYPES, etc.):
Top size: 10mm. Usual gap-gradation: 83% between 6 and 10mm, 15% between 0.09 and 2mm, 2% limestone filler passing 0.09mm DISTRESS TYPE EXTENT OR FREOUENCY LOW MEDIUM HIGH
RUTTING 1 None
LONGITUDINAL CRACKING 1 None
TRANSVERSE CRACKING 1 None
RAVELLING 1 None
ALLIGATOR CRACKING 1 None I BLOCK CRACKING 1 None POTHOLES 1 None I
NARRATIVE DESCRIPTION OF PAVEMENT CONDITION: Excellent, fresh-appearing overlay on secondary road,
(form continued on reverse side)/26 JUNE 90 DRAINAGE FACILITIES:
COMMERCIAL SOURCE (IF PROPRIETARY FEATURE):
This overlay is tradenamed COLRUG;it is marketed by the French contractor COLAS (S.A). It may be considered a proprietary formulation designed to satisfy the LCPC requirements for a very thin asphalt concrete overlay.
OTHER REMARKS: The underlying pavement surface is prepared for COLRUG with a tack coat of polymer-modified asphalt emulsion. In this case, a COLAS proprietary product, EMULCOL, was used.
POST-VISIT DEBRIEFING NOTES: These very thin asphalt overlays are used as an alternative to slurry seals to provide surface maintenance without changing the structural capacity of the pavement.
APPLICABILITY TO U.S. PRACTICE: May provide alternative to slurry and chipseals. Systems such as COLRUG have the advantage of being laid with conventional pavers.
COSTS RELATIVE TO CONVENTIONAL U.S. CONSTRUCTION PRACTICE:
Comparable to slurry seals.
35 mm PHOTOS: NO YES ROLL # NEGATIVE #‘S VIDEOTAPE: NO YES- CASSETTE # AUDIOTAPE: NO- YES- CASSETTE #
REPORTER(S): FHWA/AASHTO/NAPA SITE VISIT REPORT DATE 9-17-90 #2 DESCRIPTION OF NOVEL PAVEMENT FEATURE:
Very thin pervious asphalt wearing course.
LOCATION (COUNTRY, LOCAL GOVERNMENT UNIT, HIGHWAY #, MILEPOST):
RN 23, Le Chemin Nantais, Loire Atlantique, France
DATE OF CONSTRUCTION 7-89 LENGTH --(mi/km) # OF LANES2 ACTUAL ADT % TRUCKS EALs WHEN OPENED ACTUAL CURRENT Low DESIGNED
BRIEF DESCRIPTION OF PAVEMENT STRUCTURE (# OF LAYERS, LAYER THICKNESSES, etc): 25 mm porous asphalt overlay.
ASPHALT CONTENT_SLZ(% OF MIX) AIR VOIDS CONTENT a(%)
MODIFIER TYPE SBS Latex NOMINAL CONTENT s(% OF BINDER)
AGGREGATE DESCRIPTION (GRADATION, MATERIAL TYPES, etc.):
Top size: 10mm. Gap-gradation: 86.5% between 6 and 10mm, 12% between 0.09 and 2mm, 1.5% filler passing 0.09mm.
DISTRESS TYPE EXTENT OR FREOUENCY LOW MEDIUM HIGH
RUTTING 1 None I LONGITUDINAL CRACKING 1 None
TRANSVERSE CRACKING 1 None
RAVELLING 1 None
ALLIGATOR CRACKING 1 None
BLOCK CRACKING 1 None
POTHOLES 1 None
NARRATIVE DESCRIPTION OF PAVEMENT CONDITION: Very open appearance; no visible distress.
(form continued on reverse side)/26 JUNE 90 DRAINAGE FACILITIES:
COMMERCIAL SOURCE (IF PROPRIETARY FEATURE):
This overlay is tradenamed PERMFLEX; it is marketed by the French contractor COLAS S.A. It is proprietary formulation designed to satisfy the LCPC requirements for a thin porous asphalt overlay.
OTHER REMARKS: The underlying surface was prepared by application of a tack coat of polymer-modified asphalt emulsion. In this case, a COLAS S.A. product EMULCOL, was used.
POST-VISIT DEBRIEFING NOTES: These thin porous overlays are used for surface maintenance; they provide no additional structural capacity. The usual thickness is 40mm; the overlay here is thinner than normal to prevent frost buildup in the winter months.
The binder used in PERMFLEX is COLFLEX 253, a proprietary SBS latex-modified asphalt produced by COLAS S.A.
This overlay is placed with a conventional paver.
APPLICABILITY TO U.S. PRACTICE:
May provide a possible alternative to slurry and chip seals.
COSTS RELATIVE TO CONVENTIONAL U.S. CONSTRUCTION PRACTICE:
Uncertain. In France, polymer-modified HMA costs 20% more than conventional HMA.
35 mm PHOTOS: NO YES ROLL # NEGATIVE #‘S VIDEOTAPE: NO-YES- CASSETT’E # AUDIOTAPE: NO-YES- CASSETTE #
REPORTER(S): FH.WA/AASHTO/NAPA SITE VISIT REPORT DATE 9-17-90 #5
DESCRIPTION OF NOVEL PAVEMENT FEATURE:
FILAFLEX: A reinforced bituminous membrane, made in-situ.
LOCATION (COUNTRY, LOCAL GOVERNMENT UNIT, HIGHWAY #, MILEPOST):
Demonstrated on a parking area at a hot-mix plant west of Nantes, Loire Atlantique, France.
COMMERCIAL SOURCE (IF PROPRIETARY):
Filaflex is a patented process of SCREG Routes Group.
DETAILS OF OPERATION:
This is an in-situ manufacturing process to produce a stress absorbing membrane interlayer made up of a film of polymer-modified asphalt binder strengthened by continuous polyester-fiber threads.
It is designed for maintenance of cracked asphalt and PCC pavements. It is intended as an impervious, crack-resistent base for asphalt wearing courses.
A single, large self-propelled machine sprays polymer-modifted asphalt emulsion or binder and immediately spreads chopped polyester threads on the binder. The binder is sprayed at 0.9 to 1.5 kg/m2 while the threads are spread at 50 to 150 g/m2.
Spreader trucks follow the main unit within 2 minutes, spreading 4/6 or 6/10 granite chips at a rate of 4 to 6 liters per m’
(form continued on reverse side)/26 JUNE 90 OTHER REMARKS:
POST-VISIT DEBRIEFING NOTES:
1. The spreader truck tires pressed the chips into the polyester threads and the bituminous emulsion employed for the demonstration.
2. There was some pick-up of threads and emulsion on the truck tires.
3. The self-propelled binder/thread laydown unit costs about $600,000.
4. Since 1988, about one million m2 of FILAFLEX has been successfully laid according to the manufacturer.
APPLICABILITY TO U.S. PRACTICE:
Uncertain.
COSTS RELATIVE TO CONVENTIONAL U.S. CONSTRUCTION PRACTICE:
Considered competitive in France to other maintenance treatments designed to control reflective cracking.
35 mm PHOTOS: NO YES ROLL # NEGATIVE #‘S VIDEOTAPE: NO- YES- CASSETTE # AUDIOTAPE: NO- YES- CASSETTE #
REPORTER(S): FHJVA/AASHTO/NAPA SITE VISIT REPORT DATE 9-17-90 #4
DESCRIPTION OF NOVEL PAVEMENT FEATURE:
Deformation-resistant overlay for bridge decks.
LOCATION (COUNTRY, LOCAL GOVERNMENT UNIT, HIGHWAY #, MILEPOST):
Anne de Bretagne Bridge, Nantes, Loire Atlantique, France
DATE OF CONSTRUCTION 7-89 LENGTH --(mi/km) # OF LANES& ACTUAL ADT % TRUCKS EALS WHEN OPENED ACTUAL CURRENT Heavy High DESIGNED BRIEF DESCRIPTION OF PAVEMENT STRUCTURE (# OF LAYERS, LAYER THICKNESSES, etc): 60mm BETOFLEX overlay on PCC bridge deck
ASPHALT CONTENTx(% OF MIX) AIR VOIDS CONTENT -(%)
MODIFIER TYPE SBS Latex NOMINAL CONTENT S(% OF BINDER)
AGGREGATE DESCRIPTION (GRADATION, MATERIAL TYPES, etc.):
Top size: 14mm. Coarse aggregate and sand form continuously - graded blend. Filler content (passing 0.09mm) is 7.5% of total.
DISTRESS TYPE EXTENT OR FREOUENCY LOW MEDIUM HIGH
RUTTING 1 None
LONGITUDINAL CRACKING 1 None I
TRANSVERSE CRACKING 1 None I I I RAVELLING 1 None I I I ALLIGATOR CRACKING 1 None
BLOCK CRACKING 1 None
POTHOLES 1 None
NARRATIVE DESCRIPTION OF PAVEMENT CONDITION: No apparent distress.
(form continued on reverse side)/26 JUNE 90 DRAINAGE FACILITIES:
COMMERCIAL SOURCE (IF PROPRIETARY FEATURE):
Betoflex is a proprietary product of COLAS S.A.; it employs the COLFLEX 253 polymer-modified asphalt binder produced by COLAS.
OTHER REMARKS:
BETOFLEX is a deformation-resistant HMA designed for very heavy traffic loads on deformable support.
POST-VISIT DEBRIEFING NOTES:
APPLICABILITY TO U.S. PRACTICE:
Uncertain. Further investigations may be warranted.
COSTS RELATIVE TO CONVENTIONAL U.S. CONSTRUCTION PRACTICE:
Uncertain. In France, polymer-modified HMA costs 20% more than conventional HMA.
35 mm PHOTOS: NO YES ROLL # NEGATIVE #‘S VIDEOTAPE: NO- YES- CASSETTE # AUDIOTAPE: NO- YES- CASSETTE #
REPORTER(S): FHWA/AASHTO/NAPA SITE VISIT REPORT DATE 9-20-90 #2
DESCRIPTION OF NOVEL PAVEMENT FEATURE:
M40 Motorway construction
LOCATION (COUNTRY, LOCAL GOVERNMENT UNIT, HIGHWAY #, MILEPOST):
Extension of the M40 motorway north from oxford, Oxfordshire
DATE OF CONSTRUCTION 1989-1990 LENGTH --(mi/km) # OF LANES& ACTUAL ADT % TRUCKS EALs WHEN OPENED ACTUAL PREDICTED DESIGNED BRIEF DESCRIPTION OF PAVEMENT STRUCTURE (# OF LAYERS, LAYER THICKNESSES, etc): 40mm hot-rolled asphalt wearing course over 195mm heavy duty bitumen macadam upper road base over 125mm hot-rolled asphalt lower road base over 150mm better qualify crashed rock over 600mm crashed rock
ASPHALT CONTENTm(% OF MIX) AIR VOIDS CONTENT -J%)
MODIFIER TYPE _ MODIFIER CONTENT S(% OF BINDER) AGGREGATE DESCRIPTION (GRADATION, MATERIAL TYPES, etc.):*
Top size: 14mm. Nominal composition: 70% Crashed Stone (retained on #7 sieve). 27-28% sand passing #7 sieve, retained on #200); and 2-3% limestone filler.
* For HRA wearing course
DISTRESS TYPE EXTENT OR FREOUENCY LOW MEDIUM HIGH
RUTTING
LONGITUDINAL CRACKING
TRANSVERSE CRACKING
RAVELLING
ALLIGATOR CRACKING
BLOCK CRACKING
POTHOLES
NARRATIVE DESCRIPTION OF PAVEMENT CONDITION:
(form continued on reverse side)/26 JUNE 90 DRAINAGE FACILITIES:
COMMERCIAL SOURCE (IF PROPRIETARY FEATURE):
OTHER REMARKS:
POST-VISIT DEBRIEFING NOTES:
1. HRA wearing course employs 50 penetration grade asphalt cement.
2. HRA wearing course is batched on site. It is dressed with 20mm coated chippings applied at 12-13 kg/m?.
3. Wearing course is laid at 160-l 70°C.
4. Road base mixes are hauled from 2 hours distance in order to take advantage of the best quality aggregate. About 20,000 tons of these mixes are laid each week Road base mixes were designed to purpose rather than batched to recipe. The upper road base was required to meet a refusal density criterion of 93%.
APPLICABILITY TO U.S. PRACTICE:
COSTS RELATIVE TO CONVENTIONAL U.S. CONSTRUCTION PRACTICE:
35 mm PHOTOS: NO YES ROLL # NEGATIVE #‘S VIDEOTAPE: NO- YES- CASSETTE # AUDIOTAPE: NO- YES CASSETTE #
REPORTER(S): FHWA/AASHTO/NAPA SITE VISIT REPORT DATE 9- 14-90 #L
DESCRIPTION OF NOVEL PAVEMENT FEATURE:
SMA Overlay on heater-planed pavement surface.
LOCATION (COUNTRY, LOCAL GOVERNMENT UNIT, HIGHWAY #, MILEPOST):
Route 19, South of Schwabisch Hall, Baden- Wurttemberg, Germany
DATE OF CONSTRUCTION 9-14-90 LENGTH--(mi/km) # OF LANES2 ACTUAL ADT % TRUCKS EALS WHEN OPENED ACTUAL CURRENT DESIGNED
BRIEF DESCRIPTION OF PAVEMENT STRUCTURE (# OF LAYERS, LAYER THICKNESSES, etc): 25mm SMA overlay on heater-planed pavement.
ASPHALT CONTENTa(% OF MIX) AIR VOIDS CONTENT &.&(%)
MODIFIER TYPE Cellulose fibers MODIFIER CONTENT 0.3(% OF MIX)
AGGREGATE DESCRIPTION (GRADATION, MATERIAL TYPES, etc.): *
Top size: 8mm. Nominal gradation: 90 - 100% passing 8mm, 30 to 55% passing Smm, 20-30% passing 2mm and 8-13% filler passing 0.09mm.
DISTRESS TYPE EXTENT OR FREOUENCY LOW MEDIUM HIGH
RUTTING
LONGITUDINAL CRACKING 1 I TRANSVERSE CRACKING 1 I RAVELLING
ALLIGATOR CRACKING BLOCK CRACKING I I POTHOLES 1 I I
NARRATIVE DESCRIPTION OF PAVEMENT CONDITION:
Existing pavement showed some minor distress.
(form continued on reverse side)/26 JUNE 90 DRAINAGE FACILITIES:
COMMERCIAL SOURCE (IF PROPRIETARY FEATURE):
OTHER REMARKS:
This is considered an alternative to other possible overlay treatments.
POST-VISIT DEBRIEFING NOTES:
Paving train consisted of a heater-planer, a paver serviced from the front by a dump mix truck, and two steel- wheeled rollers.
The heater-planer heated the old pavement surface and planed it off to a predetermined depth. SMA was immediately placed and compacted. After rolling, surface of SMA looked very rich in binder so stone chippings were rolled on for extra friction. Mix occasionally showed some marking under the rollers.
Heater-planer technique is used only once due to large decrease in bitumen penetration. Next rehabilitation (in 2-3 years) will involve scarification and removal of pavement surface.
APPLICABILITY TO U.S. PRACTICE: High.
COSTS RELATIVE TO CONVENTIONAL U.S. CONSTRUCTION PRACTICE:
In Germany, SMA costs 50% more than conventional HMA.
35 mm PHOTOS: NO YES ROLL # NEGATIVE #‘S VIDEOTAPE: NO- YES- CASSETTE # AUDIOTAPE: NO- YES- CASSETTE #
REPORTER(S): FI-IWA/AASHTO/NAPA SITE VISIT REPORT DATE 9-17-90 #3 DESCRIPTION OF NOVEL PAVEMENT FEATURE:
Porous Pavement for noise reduction and rain water flow.
LOCATION (COUNTRY, LOCAL GOVERNMENT UNIT, HIGHWAY #, MILEPOST):
Boulevard Dolon, Nantes, Loire Atlantique, France
DATE OF CONSTRUCTION 7-89 LENGTH --(mi/km) # OF LANES& ACTUAL ADT % TRUCKS EALs WHEN OPENED ACTUAL CURRENT DESIGNED BRIEF DESCRIPTION OF PAVEMENT STRUCTURE (# OF LAYERS, LAYER THICKNESSES, etc): 20rnm Pervious Asphalt Wearing Course over 60mm pervious bituminous Macadam base course.
ASPHALT CONTENT_T_(% OF MIX) AIR VOIDS CONTENT “(%)
MODIFIER TYPE _T . MODIFIER CONTENT “(% OF MIX)
AGGREGATE DESCRIPTION (GRADATION, MATERIAL TYPES, etc.): *
DISTRESS TYPE EXTENT OR FREOUENCY LOW MEDIUM HIGH
RUTTING 1 None
LONGITUDINAL CRACKING 1 None
TRANSVERSE CRACKING 1 None ‘I RAVELLING 1 None
ALLIGATOR CRACKING 1 None
BLOCK CRACKING _I None POTHOLES 1 None I I
NARRATIVE DESCRIPTION OF PAVEMENT CONDITION:
The 80 mm thickness is greater than usual for pavements of this type to provide the capacity to temporarily store significant volumes of rainwater.
* See reverse (form continued on reverse side)/26 JUNE 90 DRAINAGE FACILITIES:
COMMERCIAL SOURCE (IF PROPRIETARY FEATURE):
Permflex is a proprietary thin pervious asphalt produced by COLAS S.A. COLFLEX 253 is an SBS latex- modified asphalt binder produced by COLAS S.A.
Pervious pavement is designed to reduce traffic noise and control flow of rain water.
Both courses employ gap-graded aggregate.
POST-VISIT DEBRIEFING NOTES: Wearing course Base course ---___ -T------A----- Asphalt Content 5.2% COLFLEX 253 4.8% 60/70 Bitumen -----_ ------_ -~- Air Voids Content 20% 20%
Modifier Type SBS Latex
Modifier Content 5% Nominal
Aggregate Gradation:
Coarse 86.5% 6mm - 10 mm 84% 10mm - 14mm ------_-----~ ------_------Sand 12% 0.09mm - 2mm 14.5% 0.09mm - 3mm
Filler 1.5% passing 0.09mm I 1.5% passing 0.09mm
APPLICABILITY TO U.S. PRACTICE: Uncertain, but may warrant investigation as alternative to open-graded friction courses and porous pavement.
COSTS RELATIVE TO CONVENTIONAL U.S. CONSTRUCTION PRACTICE:
Unknown. In France, polymer-modified HMA costs 20% more than conventional HMA.
35 mm PHOTOS: NO YES ROLL # NEGATIVE #‘S VIDEOTAPE: NO YES- CASSETTE # AUDIOTAPE: NO- YES- CASSETTE #
REPORTER(S): FHWA/AASHTO/NAPA SITE VISIT REPORT DATE 9- 17-90 #A
DESCRIPTION OF NOVEL PAVEMENT FEATURE:
Construction of a special overlay to prevent reflective cracking.
LOCATION (COUNTRY, LOCAL GOVERNMENT UNIT, HIGHWAY #, MILEPOST):
RN 165, Sautron, Loire Atlantique, France
DATE OF CONSTRUCTION 9-17-90 LENGTH--(mi/km) # OF LANES4 ACTUAL ADT % TRUCKS EALs WHEN OPENED ACTUAL CURRENT High DESIGNED
BRIEF DESCRIPTION OF PAVEMENT STRUCTURE (# OF LAYERS, LAYER THICKNESSES, etc): 30mm special wearing course over a 15mm special, anti-reflective cracking binder course.
ASPHALT CONTENT_IC__(% OF MIX) AIR VOIDS CONTENT JL(%/o) MODIFIER TYPE * MODIFIER CONTENT L(% OF MIX)
AGGREGATE DESCRIPTION (GRADATION, MATERIAL TYPES, etc.): *
DISTRESS TYPE EXTENT OR FREOUENCY LOW MEDIUM HIGH
RUTTING
LONGITUDINAL CRACKING 1
TRANSVERSE CRACKING RAVELLING 1 ALLIGATOR CRACKING
BLOCK CRACKING I I POTHOLES 1 I
NARRATIVE DESCRIPTION OF PAVEMENT CONDITION:
* See table on reverse
(form continued on reverse side)/26 JUNE 90 DRAINAGE FACILITIES:
COMMERCIAL SOURCE (IF PROPRIETARY FEATURE):
The binder course is a proprietary product of COLAS S.A. called SAFLEX. The wearing course is a proprietary COLAS S.A. product called RUFLEX.
OTHER REMARKS:
The wearing course uses a gap-graded aggregate. It contains no large aggregate (top size is about 3/8 inch), but the modified binder is formulated to prevent rutting. Rolling with steel-wheeled rollers left no roller marks or evidence of significant compaction.
POST-VISIT DEBRIEFING NOTES:
Wearing course Base course
Asphalt Content 5.6% COLFLEX 253 9.5% COLFLEX 253 _------~~~~----~~~~______c______---- Air Voids Content ------~~~-----~_----~~------______I_ Modifier Type SBS LATEX SBS LATEX _------~~~~~----~~---~~~~------~~~-~------Modifier Content 5% Nominal 5% NOMINAL
Aggregate Gradation: 46% 0 - 2mm Coarse 65% 6mm - 10mm 35% 2mm - 4mm ------__------___ Sand 35% 0 - 2mm 17% 0 - 3mm ROLLED SAND ~I~~~~-~~~~~~~~~~--~~~~~~~-~------~------Filler 2% Limestone
APPLICABILITY TO U.S. PRACTICE:
COSTS RELATIVE TO CONVENTIONAL U.S. CONSTRUCTION PRACTICE:
35 mm PHOTOS: NO YES ROLL # NEGATIVE #‘S VIDEOTAPE: NO- YES- CASSETTE # AUDIOTAPE: NO YES- CASSETTE #
REPORTER(S): FHWA/AASHTO/NAPA SITE VISIT REPORT DATE 9-17-90 #J-
DESCRIPTION OF NOVEL PAVEMENT FEATURE:
Chip seal constructed with modified asphalt emulsion and hot, pre-coated chips.
LOCATION (COUNTRY, LOCAL GOVERNMENT UNIT, HIGHWAY #, MILEPOST):
RN 171 Eastbound, near La Baule, Loire Atlantique, France.
DATE OF CONSTRUCTION 7-89 LENGTH3 (mi/km) # OF LANES4
ACTUAL ADT % TRUCKS EALs WHEN OPENED ACTUAL CURRENT 25,000 10 DESIGNED
BRIEF DESCRIPTION OF PAVEMENT STRUCTURE (# OF LAYERS, LAYER THICKNESSES, etc): Paver-laid chip seal. Binder layer of polymer-modified 60/70 penetration-grade asphalt emulsion applied at 0.95 kg/m” chipss spread at a rate of 25 kg/m2.
ASPHALT CONTENT N/A (% OF MIX) AIR VOIDS CONTENT N/A (%) NOMINAL MODIFIER TYPE Neoflex (SBS Latex) MODIFIER CONTENT S(% OF BINDER)
AGGREGATE DESCRIPTION (GRADATION, MATERIAL TYPES, etc.):
6mm to 1Omm chips precoated with 25 weight percent of hot sand-asphalt (5.5 % asphalt, 94.5% sand). DISTRESS TYPE EXTENT OR FREOUENCY LOW MEDIUM HIGH
RUTTING 1 None
LONGITUDINAL CRACKING 1 None
TRANSVERSE CRACKING 1 None
RAVELLING 1 None
ALLIGATOR CRACKING 1 None
BLOCK CRACKING 1 None I
POTHOLES 1 None I
NARRATIVE DESCRIPTION OF PAVEMENT CONDITION:
Pavement had an open look There was no apparent distress except for some minor tearing alone the centerline of the driving lane. Considering the traffic volume and loads, the performance was judged as very impressive.
(form continued on reverse side)/26 JUNE 90 DRAINAGE FACILITIES:
COMMERCIAL SOURCE (IF PROPRIETARY FEATURE):
The system employed for this project is tradenamed NOVACHIP, It is a proprietary product of SCREG Routes Group and conforms to the general LCPC specifications for paver-laid chipseal.
OTHER REMARKS:
POST-VISIT DEBRIEFING NOTES:
Paver-laid chip seals are intended for surface maintenance without structural effect. They seal the surface and increase skid resistance, but are substantially less noisy than conventional chip seals. It is claimed that loose chips are virtually eliminated due to the precoating and use of modified binder.
NOVACHIP is laid with a purpose-built, self-propelled unit that sprays the binder, spreads the hot, pre- coated chips and smooths the chip seal. Additional rolling is accomplished by a rubber-tired roller and a steel-wheel roller acting in tondem. This system can be applied at a rate of 3500 m2/hr at forward speeds of 0.7 mph. The paver costs approximately $800,000; there are five in operation in France.
APPLICABILITY TO U.S. PRACTICE: May provide alternative maintenance treatment for high-volume interstate and primary routes. Some similarity to chip seals applied with modified asphalt binders in Texas and New Mexico.
COSTS RELATIVE TO CONVENTIONAL U.S. CONSTRUCTION PRACTICE:
Probably higher. Costs may be offset by improved performance.
35 mm PHOTOS: NO YES ROLL # NEGATIVE #‘S VIDEOTAPE: NO YES- CASSETTE # AUDIOTAPE: NO- YES- CASSETTE #
REPORTER(S): FHWA/AASHTO/NAPA SITE VISIT REPORT DATE 9-l 7-90 #8
DESCRIPTION OF NOVEL PAVEMENT FEATURE:
Very thin asphalt concrete overlay for surface maintenance.
LOCATION (COUNTRY, LOCAL GOVERNMENT UNIT, HIGHWAY #, MILEPOST):
N 165, 30 km West of St. Nazaire, France.
DATE OF CONSTRUCTION 1988 LENGTH --(mi/km) # OF LANES& ACTUAL ADT % TRUCKS EALs WHEN OPENED ACTUAL CURRENT High DESIGNED
BRIEF DESCRIPTION OF PAVEMENT STRUCTURE (# OF LAYERS, LAYER THICKNESSES, etc): 1 Omm wearing course overlaid on existing pavement.
ASPHALT CONTENTL(% OF MIX)’ AIR VOIDS CONTENT fi(%)’
MODIFIER TYPE (SBS Latex,) MODIFIER CONTENT 5-(% OF MIX)’
AGGREGATE DESCRIPTION (GRADATION, MATERIAL TYPES, etc.):
Top size: 10mm. Usual gap-gradation: 83% between 6 and 10mm, 15% between 0.09 and 2% limestone filler passing 0.09mm.
DISTRESS TYPE EXTENT OR FREOUENCY LOW MEDIUM HIGH
RUTTING 1 None
LONGITUDINAL CRACKING 1 None
TRANSVERSE CRACKING 1 None I RAVELLING 1 None
ALLIGATOR CRACKING 1 None
BLOCK CRACKING 1 None
POTHOLES 1 None
NARRATIVE DESCRIPTION OF PAVEMENT CONDITION:
Excellent. No visible distress.
1 Nominal (form continued on reverse side)/26 JUNE 90 DRAINAGE FACILITIES:
COMMERCIAL SOURCE (IF PROPRIETARY FEATURE):
This overlay is tradenamed MEDIFLEX. It is a proprietary product of SCREG Routes Group,
OTHER REMARKS:
POST-VISIT DEBRIEFING NOTES:
These very thin asphalt concrete overlays are employed as an alternative to slurry seals to provide surface maintenance without changing the structural capacity of the pavement.
They are laid with conventional pavers.
APPLICABILITY TO U.S. PRACTICE:
May provide an alternative to slurry and chipseals. They offer the advantage of being laid with conventional paving equipment.
COSTS RELATIVE TO CONVENTIONAL U.S. CONSTRUCTION PRACTICE:
In France, comparable to slurry seals.
35 mm PHOTOS: NO YES ROLL # NEGATIVE #‘S VIDEOTAPE: NO- YES- CASSETTE # AUDIOTAPE: NO- YES- CASSETTE #
REPORTER(S): FHWA/AASHTO/NAPA SITE VISIT REPORT DATE 9-I8-90 #I DESCRIPTION OF NOVEL PAVEMENT FEATURE:
Very thin Porous Asphalt Overlay LOCATION (COUNTRY, LOCAL GOVERNMENT UNIT, HIGHWAY #, MILEPOST):
A47 Motorway South of Givois (Suburban Lyon), France.
DATE OF CONSTRUCTION 7-89 LENGTH--(mi/km) # OF LANES4
ACTUAL ADT % TRUCKS EALs WHEN OPENED ACTUAL CURRENT 80,000 winter DESIGNED 160,000 Summer BRIEF DESCRIPTION OF PAVEMENT STRUCTURE (# OF LAYERS, LAYER THICKNESSES, etc): 40mm overlay on existing pavement surface.
ASPHALT CONTENTfi(% OF MIX) AIR VOIDS CONTENT x(%)
MODIFIER TYPE Reclaimed tire rubber MODIFIER CONTENT 5-(% OF BINDER)’ treated with aromatic oil and catalyst. AGGREGATE DESCRIPTION (GRADATION, MATERIAL TYPES, etc.):
Top size: 10mm. Gap-gradation: 88% between 6mm and 10mm, 11 % between 0.09 and 2mm, 1 % filler passing 0.09mm. Aggregate is exclusively crushed porphyry.
DISTRESS TYPE EXTENT OR FREOUENCY LOW MEDIUM HIGH
RUTTING 1 None
LONGITUDINAL CRACKING 1None I
TRANSVERSE CRACKING 1 None I RAVELLING 1 None
ALLIGATOR CRACKING 1 None
BLOCK CRACKING 1None
POTHOLES 1None
NARRATIVE DESCRIPTION OF PAVEMENT CONDITION:
Appears fresh and in excellent condition. There is no apparent distress.
(form continued on reverse side)/26 JUNE 90
’ Nominal DRAINAGE FACILITIES: Adequate drainage must be provided to allow water flow through and out of the pavement surface.
COMMERCIAL SOURCE (IF PROPRIETARY FEATURE):
This project used a proprietary product DRAINOCHA PE marketed by BEUGNET Technical management. The asphalt-rubber binder is also a proprietary product, FLEXOCHAPE E, produced by BEUGNET.
OTHER REMARKS:
POST-VISIT DEBRIEFING NOTES:
This product is designed to meet the general LCPC specification for porous asphalt overlays.
The overlay is placed with a conventional paver.
APPLICABILITY TO U.S. PRACTICE: May provide a possible alternative to slurry and chip seals.
COSTS RELATIVE TO CONVENTIONAL U.S. CONSTRUCTION PRACTICE:
Uncertain. In France, modified HMA costs 20% more than conventional HMA.
35 mm PHOTOS: NO YES ROLL # NEGATIVE #‘S VIDEOTAPE: NO- YES- CASSETTE # AUDIOTAPE: NO- YES- CASSETTE #
REPORTER(S):