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OHIO HOT–MIX ASPHALT VOL. 11 NO. 2 CURRENT NEWS June, 2002 PERPETUAL PAVEMENT TASK FORCE COMPLETES PAVEMENT BUILDUP & DESIGN The task force set up by the Ohio 1 Specification ness of 16 /4 inches was selected to be used for Department of Transportation to develop spec- a CBR of 4 to 6. Weaker soils will require a Now Ready For ifications and design procedures for the perpet- new calculation or soil modification to achieve Use ual pavement concept reached another mile- a 4 to 6 CBR. This pavement is placed on 6 stone recently. Using mechanistic design mod- inches of 304 aggregate base. els, pavement thickness and buildup have now An AASHTO design for the US 30 pilot pro- 3 been established for the US 30 pilot project and ject would yield a 13 /4-inch pavement on a 6- can be transferred to other projects around the inch aggregate base so the perpetual pavement 1 state. is 2 /2 inches thicker than the AASHTO design. The thickness of a perpetual pavement is Since the thickness of a perpetual pavement calculated to limit the strain at the bottom of does not change with increased volume or axle the pavement so that it is less than the fatigue loadings, this same thickness would be used on limit of the material. This is a totally different a heavy interstate truck route where AASHTO concept than designing the pavement to with- designs are typically 18 to 22 inches. Thus a IN THIS ISSUE: stand a specified number of load repetitions perpetual pavement would be thinner than an Perpetual Pavement ....1-2 before failing as is done today. The task force AASHTO design in these cases. If you stop to chose legal load plus 20% as the critical load think about it, this makes sense. AASHTO 2nd Generation Smoothness ....................3 and 70 micro strains as the limiting strain at the designs for non-interstate routes use fewer load bottom of pavement. Using these criteria, the repetitions which give relatively thinner pave- Smoothseal Part 2..........4 material proper- Educational Seminar ....6 ties of the differ- President Bush ..............6 ent layers and a Noise Reduction.............8 linear elastic design model, TEA-21 Proposals..........9 pavement thick- I-77 Rubblization ...........9 ness was calcu- Hate Affair with Car ...10-11 lated for soil Flexible Accepts Public strengths mea- Agency Members..........11 sured by CBRs Member Spotlight ...12-13 of 4, 5 and 6. OSU Defends Title .......15 Thickness did not vary signifi- Scenic Byway................15 cantly for these Ohio Turnpike .....................16 CBRs so a stan- 2002 Annual Meeting ..17-22 dard overall Legislative Corner ..............23 pavement thick- Perpetual Pavement, continued on page 2 1 Perpetual Pavement, continued from page 1 ment sections whereas heavy interstate truck terized, and designs developed for a range of routes use a high number of axle loadings soil strengths. Much of this will be accom- which the AASHTO design equations convert plished through research projects that will to very thick pavement sections. A pavement accompany construction of the US 30 pilot pro- designed to withstand an ultimate load, as is ject. While all of this will improve the perpet- the perpetual pavement, ought to be in the mid- ual pavement design, the bottom line is that we dle some place. have a perpetual pavement specification and In our March 2002 newsletter, we detailed design that can be used today which will elim- the different materials the task force has deter- inate future reconstruction/replacement pro- mined for use in the various layers of a perpet- jects and their accompanying user delay. This ual pavement. This, combined with the thick- will be a tremendous benefit to the traveling ness determination, completes the perpetual public and was the goal that we set out to pavement design and is summarized in the accomplish when the task force was formed. graphic on page 1. While the main task has FPO would like to thank the Ohio been completed, much work still remains to be Department of Transportation for their leader- done. The process will be refined, the ultimate ship and vision in this effort. load selected will receive a more detailed analysis, the material properties further charac- 2 ODOT TO PILOT 2ND-GENERATION SMOOTHNESS SPECIFICATIONS New Spec Spurred on by a desire to make good riding A primary concern of pavement engineers with pavements even better, the Ohio Department of implementing an incentive/disincentive smooth- To Be Transportation is working with Flexible Pavements ness specification for thin asphalt overlays is how Applied To of Ohio to develop a 2nd-generation smoothness to reckon with occurrences where insufficient specification. Initially conceived to address heavy opportunities for obtaining smoothness exist. 2-Lane traffic 2-lane pavements having overlay thickness Some pavements, simply, are too rough to begin System falling below existing smoothness criteria, the new with to ever achieve the desired ride quality using specification will be applicable to all overlay thick- the specified treatment. The answer to this nesses for any pavement. quandary was a compromise specification. The A well-known fact among highway profession- draft specification adopts the incentive/disincen- als is that smooth pavements lead to happy tive pay adjustment philosophy – but with a twist. motorists. Surveys by various trade associations The incentive portion of the specification is taken throughout the years and the NQI (National from the Department’s current smoothness propos- Quality Initiative) all confirm that riding comfort is al note. The disincentive portion is taken from a high priority for today’s motorists. Ohio has Item 401.19 of the ODOT Construction & acted prudently in seeking to meet this customer Materials Specification (C&MS). desire through the implementation of incentive/dis- Under the new specification two methods of incentive ride quality specifications in the early measuring smoothness will be employed. First, the 1990s. Those ride quality specifications have California type profilograph, which is the primary resulted in superior asphalt riding surfaces and smoothness "measuring stick" used today. The high consumer satisfaction. Unfortunately, the profilograph has served Ohio well but has the lim- specs. had limitations. itation of measuring the pavement profile over a Building on the experience of the asphalt paving relatively short length – approximately 25 feet. industry and utilizing new ride quality measuring Lightweight inertial profiling devices are another tools the Ohio Department of Transportation has tool for measuring smoothness. They make possi- crafted a draft ble the use of the International Roughness Index Smoothness specs affect specification (IRI). IRI is fast becoming the national standard more than just ride quality. that addresses for measuring pavement smoothness. Using light- Smoothness specs create… previous limi- weight inertial profilers overcomes the limitations •A demand for tations. The of the profilograph, allowing for even smoother quality consciousness first genera- pavements. It is ODOT’s desire to begin using IRI tion specifica- as the smoothness "measuring stick" for all its pro- •Improved uniformity tion was jects. The drafting of this 2nd-generation specifi- in mix production, applicable to cation provides the unique opportunity of incorpo- mix delivery, mix "thick" over- rating IRI into construction projects. placement, and mix lay projects – Piloting the specification is the next step in compaction typically inter- implementing this new smoothness concept. As • Longer pavement life state jobs. this newsletter goes to print, ODOT is honing the Because much IRI criteria for incentive-based payments and seek- •Greater customer of ODOT ing projects where the new specification can be satisfaction paving work is piloted. Following the pilot projects the specifica- non-interstate, tion will be revisited, adjustments made, smoother or "thin" overlays, the advantages of using a pavements built, and happier customers made. smoothness specification could not be availed for Stay tuned to future issues of Current News as this type of construction. The new specification we follow the progress of the 2nd-generation makes that possible. smoothness specification. 3 SMOOTHSEAL - GAINING ACCEPTANCE - PART 2 State And In the September, 2001 Ohio Hot-Mix Asphalt newsletter we wrote that Smoothseal (ODOT, SS Locals Specify 854, Fine Graded Polymer Asphalt Concrete) was gaining acceptance by more agencies. We reported “Smoothseal” on projects that had recently been built by ODOT Districts in Geauga County and near Canfield. Since then the use of Smoothseal seems to have "taken off". We have heard from several other agen- cies that they have recently bid Smoothseal projects or are planning such projects. ODOT District 2 has a project, bid last year, under construction on US 6 in Henry County and another recently let on US 20A in Fulton County (Project 39-2002). The US 6 project consists of 3 trial sections. One is a true pre- Gerken Paving crew placing Smoothseal on ventive mainte- Route 6. nance candidate, that is, a pave- We'll be watching these projects to confirm that ment in struc- they continue the durable, cost-effective perfor- turally sound mance we have come to expect from Smoothseal. condition needing Elsewhere in this newsletter you will find a tech- only surface nical bulletin on the appropriate application of maintenance; a Smoothseal. This document is intended to assist second, which agencies that are considering Smoothseal projects to requires more choose the proper application, that is, the right treat- extensive mainte- ment for the right conditions and at the right time. Smoothseal placed on the Route 6 project last fall. nance, that will If your agency is planning a Smoothseal project, see the SS 854 we'd like to hear about it. Please give us a call, toll placed over a leveling course; and a third section, free, 888-446-8649 (Ohio only) or e-mail which will be milled before placing the Smoothseal.