82 10/12/82 7/13/82 to EORGIA INSTITUTE OF

EORGIA INSTITUTE OF TECHNOLOGY OFFICE OF CONTRACT ADMINISTRATION PROJECT ADMINISTRATION DATA SHEET

I x ' ORIGINAL I I REVISION NO.

oject No. E- 20- 657 GTR Wax DATE 9123/82 roject Director: Dr. Q. L. Robnett School Civil Engineering ponsor: Southern Company Services, Inc.

ype Agreement: SCS Contract No. 195-82-009 ward Period: From 7/13/82 To 82 (Performance) 10/12/82 (Reports) 3', ponsor Amount: Total Estimated: $ 8,211 Funded: S 8,211

t Sharing Amount: $ 3,581 Cost Sharing No: E - 20 - 333 itle: Development of a Technical Data Base Concerning Use of Boiler Bottom Waste as awing Material

DMINISTRATIVE DATA OCA Contact Faith G. Costello

Sponsor Technical Contact: 2) Sponsor Admin/Contractual Matters: r. Randall E. Rush Lamar C. Larrimore outhern Company Services, Inc. Contract Administrator .0. Box 2625 Southern Company Services, Inc. irmingham, AL 35202 P.O. Box 2625 Birmingham, AL 35202

put . add 1 Ly. to Zfaiaa6cr, Con- tracts Services)

ense Priority Rating: N/A Military Security Classification: industrial (See below ) (or) Company/Industrial Proprietary: STRICTIONS

Attached N/A Supplemental Information Sheet for Additional Requirements.

vel: Foreign travel must have prior approval — Contact OCA in each case. Domestic travel requires sponsor

approval where total will exceed greater of $500 or 125% of approved proposal budget category.

uipment: Title vests with Sponsor: however, none proposed.

MMENTS: advertising or publicity matter with any reference to SCS. Inc. or any wholly owned bsidia of same ma be made without •rior wri s .val .f

ES TO:

arch Administrative Network Research Security Se rvices Research Communications (2) arch Property Management (eports Coordinator (OCA Project File nting GTRI Other rement/EES Supply Services Library Other

kl rtn w a. sr, I co.... rs0 ■11 in

GEORGIA INSTITUTE OF TECHNOLOGY OFFICE OF CONTRACT ADMINISTRATION

SPONSORED PROJECT TERMINATION SHEET

VI;

Date 3/17/83

Project Title: Development of a Technical Data Base Concerning Use of Boiler Bottom Waste as Paving Material Project No: E-20-657

Project Director: Dr. Q. L. Robnett

Sponsor: Southern Company Services, Inc.

Effective Termination Date: 11/30/82

Clearance of Accounting Charges: 11/30/82

Grant/Contract Closeout Actions Remaining:

Final Invoice VfillftitiiiifirtgMfkiiiit

❑ Final Fiscal Report

Final Report of Inventions

Govt. Property Inventory & Related Certificate

Classified Material Certificate El Other

Assigned to: Civil Engineering Okhool/habwraMMO

COPIES TO:

Administrative Coordinator Research curl EES Public Relations (2) Research Property Management C-- Reports Coordinator (OCA) Computer Input Accounting Legal &iiiices-tOCA)'— Project File Procurement/EES Supply Services Library Other Robnett

FORM OCA 10:781 SCEGIT-83-106

USE OF BOILER BOTTOM: AH AS A PAVING MATERIAL - A TECHNICAL DATA BASE

FINAL REPORT AE

SUBMITTED, TO

SOUTHERN COMPANY SERVICESA

DR, QUENTIN L. ROBRETTr PHD, PE SCHOOL OF CIVIL ENGWERING GEORGIA INSTITUTE 6FIgCHNOLOGY

GEORGIA INSTITUTE OF TECHNOLOGY A UNIT OF THE UNIVERSOYSYSTEM OF GEORGIA SCHOOL OF COM fNGINEERING ATLANTA, FIGIA 30332 SCEGIT-83-106

USE OF BOILER BOTTOM ASH AS A PAVING MATERIAL - A TECHNICAL DATA BASE

FINAL REPORT - PHASE I

Submitted to

Southern Company Services

Dr. Quentin L. Robnett, PhD, PE School of Civil Engineering Georgia Institute of Technology

January 1983 SUMMARY

Tremendous quantities of materials, particularly aggregate, are used annually in the construction and maintenance of highways. Depletion and/or shortages of aggregates in many areas of the Southeast have contributed to a spiraling financial burden on highway agencies. New and non-specification materials are constantly being examined as to their potential for use in roadways.

Bottom ash has not experienced much use, particularly in the Southeast, but appears to have excellent potential as a source of highway construction aggregate. The Southern electric system produces almost one million tons of bottom ash annually and currently has an estimated 50 million tons of pond ash (fly ash plus bottom ash) in storage at the 20 coal-fired power plants in its service area.

Considerable technical information is required in order to gain acceptance and widespread use of bottom ash by various highway agencies. Specifi- cally, the following types of information are needed: (a) character of the existing and new bottom ash resources, (b) properties and characteristics of various paving mixtures containing bottom ash, (c) potential performance of bottom ash mixtures in typical pavement structures, and (d) relative economics of bottom ash mixtures compared to other conventional paving materials.

A two-phased research study has been initiated to develop the broad range of information and technology necessary to promote the use of bottom ash as an acceptable alternate paving material. This report contains the findings of PHASE I, Development Of A Technical Base For Use Of Boiler Bottom Ash As A Paving Material. In this phase, information has been collected from the technical literature, Southern system member companies, and discussions with many individuals who have experience with the nature and use of bottom ash materials in paving mixtures.

The information has been summarized and presented in this report, with an interpretation of this data relative to the Southern system. Discussions include identification of problems and uncertainties associated with the use of bottom ash as a paving material in the general region encompassed by the Southern system.

Based on the findings of this study to date, it appears that bottom ash produced by the Southern system has excellent potential for use in paving mixtures. Before maximum utilization and widespread acceptance of this bottom ash can be realized, however, a substantial amount of information must be developed. It is recommended that a second phase of the research study be pursued with an overall objective of developing this information. Spe- cific objectives of the PHASE II research study have been presented in this report and include: (a) establish availability and character of existing and new bottom ash, (b) evaluate engineering properties of paving mixtures containing bottom ash, (c) predict performance of and develop pavement design information for mixtures containing bottom ash, (d) develop specifications for bottom ash materials and mixtures containing bottom ash, and (e) examine the economics of using bottom ash in paving mixtures, both from the perspective of the consumer and the producer. TABLE OF CONTENTS

Page

CHAPTER 1 - INTRODUCTION 1

1.1 GENERAL BACKGROUND 1 1.2 OVERALL RESEARCH OBJECTIVE AND SCOPE 7 1.3 RESEARCH PLAN 7 1.4 PURPOSE OF THIS REPORT 8 1.5 RESEARCH APPROACH 8 1.6 ORGANIZATION OF REPORT 9 CHAPTER 2 - POWER PLANT ASH 10 2.1 GENERAL 10 2.2 SOURCES OF BOTTOM ASH AND PYRITE 11 2.2.1 BOTTOM ASH 11 2.2.2 PYRITE 24 2.3 PRODUCTION OF BOTTOM ASH 26 2.4 PROPERTIES OF BOTTOM ASH 26 2.4.1 PHYSICAL PROPERTIES 27 2.4.2 CHEMICAL PROPERTIES 30 2.4.3 ENGINEERING PROPERTIES 32 2.5 DISCUSSION 46 CHAPTER 3 - USE OF BOTTOM ASH AS PAVING MATERIAL 49 3.1 GENERAL 49 3.2 BASIC REQUIREMENTS OF PAVING MATERIALS 50 3.3 SELECTED EXAMPLES OF FIELD APPLICATION 53 3.3.1 BOTTOM ASH AS UNSTABILIZED AGGREGATE 53 3.3.2 CEMENT OR LIME STABILIZED BOTTOM ASH 55 3.3.3 ASPHALT MIXTURES CONTAINING BOTTOM ASH 64 3.4 OTHER PERTINENT STUDIES 72 3.5 MATERIAL AND CONSTRUCTION SPECIFICATIONS FOR BOTTOM ASH. . 77 3.5.1 GENERAL CONSIDERATIONS AND DISCUSSION 77 3.5.2 EXISTING SPECIFICATIONS AND GUIDELINES 79 3.6 DISCUSSION 81 CHAPTER 4 - ECONOMICS ASSOCIATED WITH BOTTOM ASH USE 86 4.1 INTRODUCTION 86 4.2 GENERAL CONSIDERATIONS 86 4.2.1 PRODUCER 86 4.2.2 CONSUMER 88 4.3 SPECIFIC EXAMPLES 89 4.4 LIFE CYCLE COSTS - GENERAL CONSIDERATION 92

CHAPTER 5 - ENVIRONMENTAL CONSIDERATIONS 93 5.1 GENERAL 93 5.2 EFFECTS OF REMOVING ASH FROM PONDS 93 5.3 CLASSIFICATION OF ASH IN REUSE APPLICATIONS 94 TABLE OF CONTENTS (Continued)

Page

CHAPTER 6 - CONCLUSIONS AND RECOMMENDATIONS 95 6.1 GENERAL 95 6.2 ATTRACTIVENESS OF BOTTOM ASH USE 96 6.3 PROBLEMS AND UNCERTAINTIES ASSOCIATED WITH USE OF BOTTOM ASH 97 6.4 RECOMMENDATIONS 98 REFERENCES 100 APPENDIX A A-1 APPENDIX B B-1 LIST OF FIGURES

Figure Page

1.1 U.S. Regions with Potential for Conventional Aggregate Shortage 2

1.2 Areas of the Southeast with Potential for Aggregate Shortage 3

2.1 Schematic Diagram of Typical Coal-Fired Electric Generating Plant 12

2.2 Typical Gradation Curves for Dry Bottom Ash from West Virginia and Georgia 25

2.3 Variations in Chemical Composition of Flyash and Bottom Ash 31

2.4 Degradation Displayed by Two Bottom Ash-Bituminous Mixtures after Drop-Hammer Compaction 47

3.1 Grain Size Distribution of Five Bottom Ash and Two Flyash Materials Used in Special Cement Treatment Study 57

3.2 Contours of Equal Marshall Stability for Various Sand-Bottom Ash-Asphalt Mixtures 67 3.3 Theoretical Gradations Producing Maximum Density 84

4.1 Alternate Pavements Approximately Equivalent in Design Performance with Associated Initial Cost Per Square Yard 91

LIST OF TABLES

Table Page 2.1 Summary of General Information for Coal-Fired Power Plants in the Southern Electric System 13

2.2 Summary ofInformation Concerning Ash Produced in the Southern Electric System 18 2.3 Summary of Pyrite Handling at Georgia Power Company Plants 22 2.4 Specific Gravity and Water Absorption Test Results from FHWA Study 29 Ash Chemical Analyses for a Large Number of 2.5 U.S. Coals 33 2.6 Los Angeles Abrasion and Soundness Test Results from FHWA Study 44 Properties of Aggregate that Influence Specific 3.1 Functions 52 3.2 Summary of Results from Compressive Strength Tests on Cement Treated Base Coarse Materials with Dry Bottom Ash, Flyash, or Limestone Aggregate 58

3.3 Laboratory Test Data from Studies of Treated Bottom Ash as a Base Material - Georgia Department of Transportation 74 USE OF BOILER BOTTOM ASH AS A PAVING MATERIAL - A TECHNICAL DATA BASE

CHAPTER 1

INTRODUCTION

1.1 GENERAL BACKGROUND

Tremendous quantities of materials, particularly aggregate, are used annually in the construction and maintenance of highways at all levels of the almost 4,000,000 mile United States roadway network. In 1981, about 50% of the total aggregate consumption (- 500,000 tons) was used nationally in the highway construction industry; the U.S. Bureau of Mines suggests that the overall need for highway aggregate will double by the year 2000. Total projected annual demand for aggregate in the construction industry will approach

2 billion tons by the start of the 21st century.

An as example of current use, in 1981 the Georgia DOT signed contracts on work which would require over 3 million tons of crushed aggregate for base and

subbase applications and almost 7 million tons of asphaltic concrete [63].

With the active construction industry in the southeastern part of the U.S., it

is reasonable to assume that future growth of aggregate demand will also occur

in this region.

Rising energy costs related to transportation, together with shortages of aggregate in many areas, have contributed to a spiraling financial burden on

highway agencies. Figures 1.1 and 1.2 depict the areas in the continental

United States and the southeast where aggregate shortages presently exist, assuming haul distances will exceed 40-50 miles [28]. It can be noted that many areas of the southeast, particularly the coastal areas, are experiencing aggregate shortages. The extent of such shortages has risen in recent years as a result of drastically increased transportation costs. It is not unusual

1 Aggregate Shortage Areas

Cross hatched areas represent regions located more than 40 miles from existing aggregate supply

Figure 1.1. U.S. Regions with Potential for Conventional Aggregate Shortage (Ref. 28).

2 Areas with aggregate shortage

Coal-fired power plants in the Southern electric system

Figure 1.2. Areas of the Southeast with Potential for Aggregate Shortage (Ref. 28). for transportation charges for imported aggregate to far exceed the cost of the aggregate. During the construction of Interstate 95 along the Atlantic coast of Georgia and Florida, in many areas the aggregate was transported more than 250 miles. In northern Florida, the cost of importing high quality aggregate from the Piedmont region often exceeds $10 to $20 per ton (for transportation alone) [64].

Compounding the fiscal picture for highway construction, most highway agencies are having problems with inflation and dwindling highway tax revenues caused by reduced gasoline consumption and more fuel efficient vehicles. The need for conserving financial resources is more evident than ever, yet the highway industry is faced with the need for new facilities as well as an increasing maintenance problem with existing facilities.

A strong indication of the concern over cost and availability of high quality paving materials is reflected in the number of publications, research efforts, and symposia on the subject. These publications and other efforts clearly show than many new or non-specification materials have excellent potential for use in highway construction and maintenance.

One material that has not experienced much use but appears to have excellent potential as a source of highway construction aggregate [28] is the waste material or solid residue that is left after coal combustion at coal-fired power plants. Whether this material should be called waste is debatable, but to be consistent with most published works in the area, it will be called waste here. The solid residue from this coal-burning process normally consists of two distinct fractions; the finer fraction is commonly called "flyash" and the coarser fraction is often referred to as "bottom ash". Extremely large quantities of these two materials are generated. On a national scale over 500 million tons of coal are burned, with collection of about 50 million tons and

4 18 million tons of flyash and bottom ash, respectively [30,46]. The Southern electric system currently operates 64 generating units which on an annual basis burn in excess of 35 million tons of coal and produce more than 4 million tons of ash.

Both flyash and the more granular bottom ash have been used as paving materials. Bottom ash has been used as base course aggregate in both untreated and treated (with lime and flyash, cement, or asphalt) states. Exten- sive use has been made in the West Virginia area, where Professor R. D. Seals and his associates at the University of West Virginia are considered pioneers in the characterization and development of uses for bottom ash. Majidzadeh, et al. [2,16,17] recently completed a study sponsored by the Federal Highway

Administration, the objective of which was to characterize bottom ash and evaluate it as an aggregate for use in asphalt mixes. Bottom ash mixed with by-product lime was used successfully as a base course for a recently completed road at Georgia Power's Rocky Mountain Project in northwest Georgia [57].

Extensive use has been made of cement treated bottom ash for base course construction in West Virginia [44].

The concept of using bottom ash as a paving material is appealing not only from the standpoint of possible cost savings to those using the material but also from the standpoint of providing a way to reduce the amount of solid waste that must be either disposed of or stored by power companies.

Disposal and/or storage of ash is a major expense to power companies.

Estimated disposal costs for the electric utility industry in 1980 ranged from

$375 million to 5740 million. On a national scale, disposal costs range from

$5 to $10 per ton of ash [61]. Georgia Power has estimated its disposal costs

for various power plants. These costs (1981), which include operating and maintenance expenses plus depreciation expenses, ranged from $4.23/ton (Wansley)

5 to as high as $14.82 per ton (Arkwright), with an overall unweighted average of $9.12 per ton [70].

Development of markets or alternate, but economical, methods of disposal for the ash material, is of major interest to the Southern electric system.

If a market were available for these waste materials, disposal costs might be dramatically reduced. Flyash currently is a marketable and widely used material in various geographical areas. The coarse fraction (bottom ash) is more widely used; however, the portion not marketed presents, along with the finer ash at certain plants, a major disposal problem. Disposal ponds requiring large amounts of land are needed. When these ponds become filled, either the ash material must be removed at considerable cost or new ponds must be constructed, also at considerable cost.

Acceptance and use of "new" materials such as bottom ash in lieu of conventional materials normally require considerable technical development and engineering evaluation. A comparison of properties, characteristics, and potential behavior of waste materials such as bottom ash to conventional and

"time-tested" paving materials is normally required. Ultimately, specifications must be developed if the material is to be accepted as an alternate to conventional materials. Such specifications are important to ensure quality since these ash materials are not manufactured, but rather are the material that is left at the end of the coal consumption cycle. Specifically, with respect to bottom ash produced at Southern system plants, the following types of information must be developed before rational decisions can be made concerning its use:

1. character of the existing and new bottom ash resources at the various power plant sites.

2. properties and characteristics of various paving mixtures containing bottom ash.

6 3. potential performance of bottom ash mixtures in typical pavement structures.

4. relative economics of bottom ash compared to other conventional paving materials.

1.2 OVERALL RESEARCH OBJECTIVE AND SCOPE

The general objectives of the research study initiated in July, 1982 by the School of Civil Engineering, Georgia Institute of Technology, are to

(a) investigate and establish the feasibility of using bottom ash as a paving material and (b) establish sufficient technical information to facilitate development of specifications and a usage strategy. Both existing deposits of bottom ash and "new" or processed (disposal control) bottom ash need to be evaluated.

1.3 RESEARCH PLAN

The objectives of this study will be accomplished by a multiple task, two phase program. The program is tailored such that both Georgia Tech and the

Southern system companies are involved.

Specific work tasks for the total research program are:

PHASE I

Task A - Development of Technical Data Base

Task B - Preparation of Report and Detailed Research Plan

for PHASE II

PHASE II

Task C - Sampling Program

Task D - Laboratory Evaluation of Properties and Characteristics

of Bottom Ash

Task E - Laboratory Evaluation of Bottom Ash Mixtures as a Paving

Material

7 Task F - Field Demonstrations (Optional)

Task G - Analysis and Interpretation of Test Results

Task H - Investigation of Environmental Effects

Task I - Prepare Report and Present Significant Findings

1.4 PURPOSE OF THIS REPORT

The primary purpose of this report is to integrate into a written document the findings of Phase I, Task A - Development of a Technical Data Base for Use of Boiler Bottom Waste as a Paving Material.

1.5 RESEARCH APPROACH - PHASE I

Pertinent technical literature and information were collected and studied.

Sources of technical literature and information included the following:

1. Proceedings of Ash Utilization Symposia (1957, 1970, 1973, 1976,

1979, 1982).

2. Highway and Transportation Research Board publications.

3. ASCE Journals (Transportation, Geotechnical).

4. Federal Highway Administration reports.

5. Bureau of Mines publications.

6. Publications from the Electric Power Research Institute (EPRI).

7. Information from Southern system member companies.

8. Laboratory information from Georgia Department of Transportation.

9. Field visit to West Virginia.

Based upon the information collected, the technical data base report has been developed; this report not only presents information, results, findings of other studies, etc., but also interprets them relative to the potential for use of Southern system bottom ash as a highway construction material.

8 1.6 ORGANIZATION OF REPORT

This report is organized in a manner so as to efficiently present and interpret the current state-of-the-art. Chapter 2 discusses bottom ash as a material; Chapter 3 presents available information concerning the use of bottom ash as a paving material; Chapter 4 addresses the general aspect of economics; Chapter 5 is a general evaluation of environmental concerns and impact; and Chapter 6 is an overall summary and interpretation. Appendices are attached which include certain existing specifications and other pertinent information concerning bottom ash use.

9 CHAPTER 2

POWER PLANT ASH

2.1 GENERAL

Approximately 40% of the electricity generated in the United States is produced at power plants which burn coal. East of this Mississippi River, over 85% of electricity comes from coal-fired power plants [30]. In the

Southern System, about 85% is coal-generated.

As coal is burned at one of these plants between 4 and 20% is typically left unburned as residue [39]. This residue is composed predominantly of either fly ash, which is carried out of the furnace by the flue gases, or bottom ash, which is the heavier residue that drops to the bottom of the furnace.

The nature (chemical, physical, and engineering properties) of both fly ash and bottom ash are of interest to potential users in the highway industry.

The nature of the ash is controlled by a number of factors including [6]:

1. type and variability of coal composition

2. degree of pulverization

3. type of furnace

4. firing temperature and other operating parameters

5. characteristics and operation of ash collection and disposal system

6. environmental effects (e.g., leaching, weathering, self-hardening,

etc.)

The primary purpose of this chapter is to discuss in some detail the production and nature of coal ash, including bottom ash of the type produced by the plants within the Southern system.

10 2.2 SOURCES OF BOTTOM ASH AND PYRITE

2.2.1 Bottom Ash

Most coal-fired power plants in operation today use pulverized coal or cyclone furnaces (stoker furnaces are not common in electric utility applications today). In these types of plants, the furnaces are fired with a finely- divided coal. The coal is either crushed or pulverized in a rolling or ball mill until over 70-80% passes the No. 200 sieve [39]. In a pulverized coal furnace, the mixture of pulverized coal and air is injected into the boiler where combustion takes place almost instantly. The intense heat of this combustion process (2000°F to 3500°F) burns most of the coal but the mineral portion of the coal is left unburned as ash. The fine particulate mineral matter plus any unburned coal particles (the composite is called fly ash) are carried out of the boiler by the flue gases. Particulate collection devices such as electrostatic precipitators (Figure 2.1) and baghouses are used to remove fly ash from the flue gases.

A portion of the ash collects on the furnace walls and falls or runs down to the furnace bottom, 'where it is collected and removed from the furnace by various methods. This material is called bottom ash. The percentage of total ash collected as bottom ash varies with the type of furnace but is generally as follows [6]:

Pulverized Coal Burners

. Dry Bottom 20-25% Bottom Ash

. Wet Bottom 40-50% Bottom Ash

Cyclone Burners 90% Bottom Ash

All plants in the Southern electric system use dry bottom, pulverized coal furnaces. Table 2.1 summarizes general power plant and coal characteristics for the Southern system.

11 Coal Pulverizer

Dry Heater Air Bottom Precipitators Magnetic Boiler Field

Stack

Flame

00 4 60 0 o

00 0 d 0 0 0 eft' 0 0 0: 00 d 0

Gas Flow Bottom Blower Ash

Ash Hoppers

Crusher

To Disposal

Figure 2.1. Schematic Diagram of Typical Coal—Fired Electric Generating Plant (Ref. 39). SUMMARY OF GENERAL INFORMATION FOR COAL-FIRED POWER PLANTS IN THE SOUTHERN ELECTRIC SYSTEM

Company Generating Number Boiler Typea Ash Content and Capacity of and Coal Burg, Coal of Coal Plant MW nits Manufacturer Tons (10') Source (% Range and Period) - , ALABAMA POWER 9.78 - 15.7 (1977 - 1982) Barry 1525 Lo CE 2100 C\J

Gadsden 120 LO CE 248

Gaston 1880 k BW 4089 _ .0 C Gorgas 1281 CE/BW 2725 \I

Greene Co. 500 BW/Riley 732 primarily ■ — I Miller 660 BW 1106 bituminous coal from GEORGIA POWER various 9.78 - 12.9 sources (1980) c d -

Arkwright 160 cl CE/B&W 281 -

Bowen 3160 c1 CE 7241 - Branch 1540 cl BW/Riley 2843 -

Hammond 800 CV BW/FW 1398

McDono4h 490 0 CE 1119 McManus 115 .1 C - 135(1973) O —

Mitchell 170 BW/CE 428 .-1

Scherer 818 CE 710 C Wansley 173C V CE 4232 t - -- - Yates 125C CE 2845

GULF POWER 10.3 - 12.8 (1977 - 1980) ct

Crist 97C CV Riley/CE/FW 1622

Scholz 8C C BW 103 V

Smith 305 CE 823

MISSISSIPPI POWER 9.00 - 12.61 (1975 - 1980) CV

Daniel 1000 C CE 1730 Watson 750 V CE/Riley/FW 1441

------lapAll Southern system boilers burn pulverized coal Information obtained from the operating companies indicates that the coal sources have varied substantially both between and among plants and also from year to year. Plants in the Southern electric system burn predominantly bituminous (Class II) coal. cNow 01-fired In the slag or wet bottom cyclone furnace, ash collected at the bottom of the furnace is maintained in a liquid condition by maintaining a temperature well above the slag's fusion point [39]. Such slag temperature may be from

1900°F - 3000°F [39]. A slag tank or water-filled pit is positioned below the furnace to receive the tappings of molten slag from the furnace. The resulting product is often called wet bottom ash, boiler slag, bottom slag, or "Black

Beauty." It is glassy and angular in appearance, resembling angular, crushed dark glass.

The dry bottom furnace, formed with a hopper bottom (Figure 2.1) has sufficient cooling surface so that ash which impinges on the furnace walls or on the hopper bottom is solid and essentially dry. These furnaces generally

have open grates at their bases and below the open grates a water - filled ash pit is positioned to receive ash from the furnace. A certain amount of ash will also form on the internal walls of the boiler and will find its way into the ash pit and be quenched much like the wet bottom ash. However, a large portion of the bottom ash is collected in an essentially dry state and as such has physical characteristics different than the wet bottom slag. Generally, the dry bottom ash is quite angular and has a porous surface texture.

Another part of the dry bottom ash handling system is a crusher or clinker grinder, Figure 2.1. This crusher is used to reduce the size of larger particles to accommodate sluicing of the bottom ash. The maximum size of bottom ash particles depends primarily on the crushing equipment. Ratcliffe [71] indicates that the grinder normally reduces clinkers to 1/2 inch or finer at

Georgia Power Company plants. With wear of the grinder, maximum size may be slightly larger, however.

It has been reported [2,32,33] that at least part of the dry bottom ash is actually composed of loosely sintered flyash particles which are soft and

14 friable and which can break down into fine fly ash dust. Kinder [44] for example, reports that one American Electric Power (AEP) plant in West Virginia has a "supercritical" boiler that produces large amounts of "popcorn" ash

(loosely sintered). It is not known whether "popcorn" ash is produced at plants within the Southern system.

Disposal of the collected ash presents a major problem since utilization of these ash materials is commonly far less than the quantities collected.

Faber [45] reports that on a national scale, ash utilization is 18%, 34% and

59%, respectively, of the total quantities produced for fly ash, bottom ash, and boiler slag. For the Southern system, far less than 34% of the bottom ash is sold.

Both wet and dry methods are commonly used for disposal of power plant ash. In the dry method, ash materials are collected and periodically removed by some method of transport such as trucks. In the wet disposal method, the ash is sluiced with water to a pond or lagoon. At some plants, both methods are used (dry for fly ash and wet for bottom ash), whereas at other plants only wet methods are used. In the wet method, fly ash and bottom ash can be

"codisposed" within the same pond, or can be separated and placed in separate ponds (or at different locations within the same pond).

The disposal method used can greatly affect the relative uniformity of grain size within a pond. For example, codisposal of fly ash and bottom ash results in a substantially different gradation of pond ash materials than if the two ash materials are kept separated.

Of obvious interest in development of utilization strategy for existing pond ash is a knowledge of the nature and characteristics of the ash deposits within ponds. Since, normally, the ash has been considered a "waste" material, little information is available as to the history of deposition within various ponds. In general, there has been no need to be concerned about controlling

15 the physical or mechanical characteristics of the ash material. Historically, disposal of waste material was accomplished with the least amount of effort and expense possible.

Kinder [44] is a strong advocate of dry disposal of flyash accompanied by compaction because of the substantially greater density that can be obtained compared to wet disposal; the higher density means that more ash can be placed

in a given volume at a disposal facility.

When ash is sluiced to an ash pond, it is transported in a pipe or pipes by a relatively large quantity of water. The ash-water blend is dumped into

the ash pond, normally at the pond's edge. Ash is removed from the transport water by gravity separation within the ash pond. Many factors affect the efficiency of removing suspended solids in ash ponds including turbulence,

hydraulic distribution and loading, liquid retention time, and the settling

characteristics of the suspended solids [11].

To a great extent, the rate at which the suspended solids are deposited,

and the resulting gradation of materials with distance from the sluice pipe

(size gradient), are related to the size and density of the suspended solids

and the velocity of the transporting medium (water).

In general, larger particles settle out more rapidly than the smaller

particles; hence, the coarser bottom ash will be deposited fairly close to the

sluice pipe outfall whereas the finer particles will be carried a greater

distance from the discharge point.

Compounding the depositional situation is the fact that ash ponds are

constructed in various sizes and shapes depending on site conditions. Some

basins are irregular in shape whereas others constructed on flat around have a

more regular shape. In addition to physical dissimilarities, the operating

16 conditions of the ash pond can vary greatly. For example, the water level in some ponds is raised incrementally as ash is deposited, while in other ponds the water is kept at a constant level. Periodic dredging also affects the distribution of ash within a pond.

In addition, the discharge point for the ash sluice pipe can be changed from time to time in order to somewhat equalize the rate at which different areas of the ash pond are filled. This can lead to overlapping fans of coarse and fine material which vary in grain size not only horizontally but also vertically. Table 2.2 presents a summary of ash handling and disposal procedures in the Southern system.

This potential heterogeneity of grain size within a given ash pond may have a major impact on the general use potential for the ash materials.

Specialized methods and/or strategies may be required to render the ash a marketable resource.

Head and Seals [12] for example, report on acquisition of bottom ash from a pond by using a washing and screening operation. Usmen and Anderson [22] report that ponding of the ash may produce undesirable segregation as the finer material is deposited farthest from the discharge pipe; however, they report that segregation is used to advantage by one West Virginia operator who uses the ponding to remove some fines from the ash. They further suggest the desirability of disposing of the ashes separately in order to reduce handling and gradation variations.

It appears that the use of bottom ash from uncontrolled ash ponds in asphaltic concrete mixtures may be the most difficult of possible applications, due to the need for more stringent gradation control. However, if the bottom ash is stabilized with lime or cement, it is possible that substantial variations in gradation may be tolerated. Kinder [44], for example, reports that

TABLE 2.2 SUMMARY OF INFORMATION CONCERNING ASH PRODUCED IN THE SOUTHERN ELECTRIC SYSTEM

ALABAMA POWER

BARRY GADSDEN GASTON GORGAS GREENE CO. MILLER Ash Production-1981 (10 3 tons) FA 294 37 449 253 51 115 BA 52 7 80 45 16 7 Ash Handling Method FA FW FW FW/FD FW FW FW BA BW BW BW BW BW BD Ash Disposal Method and Frequency CoD CoD CoD SD CoD CoD FA int int int int int int BA int int int int int int Pyrite Handling Method Current CoD CoD CoD CoD CoD CoD Past CoD CoD CoD CoD CoD CoD Ash in Storage b (10 3 tons) Flyash & Bottom Ash 5500 1000 8000 5400 1100 500

Remaining Life at Disposal Sites (years) 15 20 1.5 18 23 30 Bottom Ash Properties Gradation NA NA NA NA NA NA Max. Particle Size (inch) <1/4 <1/2 <1 <1 NA <1/16 Coeff. of Uniformity NA NA NA NA NA NA Specific Gravity NA NA NA NA NA NA

isposal Costs c - 1981 NA $4.55 $5.85 $2.35 $2.06 $4.23 ( per ton) (O&M) (O&M) (O&M) (O&M) sh Sales - 1981 (103 tons) FA N 28 BA 1 3 N N N N N

h Agreements - expiration FA 1987 N 1983 N NA BA 1984 N N N NA

18 TABLE 2.2(Continued)

SUMMARY OF INFORMATION CONCERNING ASH PRODUCED IN THE SOUTHERN ELECTRIC SYSTEM

GEORGIA POWER

ARK BOWEN BRANCH HAM McD McM MIT SCH WANS YATES

Production-1981 3 Oil- 0 tons) Fired 1982 FA 37 602 270 132 109 Since 40 Start- 374 287 BA 9 150 68 33 27 1973 10 up 93 72 Handling Method FA FW/FD FW/FD FW FW FW/FD FW FW FW FW/FD FW BA BW BW BW BW BW BW BW BW BW BW

Disposal Method Frequency CoD SD CoD CoD SD CoD CoD CoD CoD SD FA cont cont cont cont cont cont cont cont cont cont BA int int int int int int int int int int ite Handling Method Current Past }See Table 2.3 for Georgia Power information. b in Storage 3 0 tons) Flyash & Bottom Ash 1700 6600 4900 2900 2500 400 1100 2300 6100 aining Life at Contino posal Sites (years) 5 7.5 27 5 17 - 27 26 46 Dredgin tom Ash Properties adation NA NA NA NA NA NA NA NA NA NA x. Particle Size (inch) <1/2 <1/2 <1/2 <1/2 NA <1/2 <1/2 <1/2 <1/2 <1/2 or < eff. of Uniformity NA NA NA NA NA NA NA NA NA NA cific Gravity NA NA NA NA NA NA NA NA NA NA osal Costs c - 1981 r ton) $14.82 $6.03 $9.02 $9.11 $8.64 - $11.57 - $4.23 $9.54 Sales - 1981 3 tons) FA 3 }223 N N 32 N N N 68 BA N N 40 N N N N }2.7

Agreements - expiration FA 1998 1998 1998 N 1998 N N N 1998 1998 BA N 1998 1998 N 1992 N N N N 1998 Abbreviations for plant names

ARK - Arkwright HAM - Hammond McD - McDonough McM - McManus MIT - Mitchell SCH - Scherer WANS - Wansley

19 TABLE 2.2(Continued) SUMMARY OF INFORMATION CONCERNING ASH PRODUCED IN THE SOUTHERN ELECTRIC SYSTEM

GULF POWER MISSISSIPPI POWER CRIST SCHOLZ SMITH DANIEL WATSON

Ash Production-1981 (10 3 tons) FA 152 20 93 104 95 BA 51 2 23 19 17

Ash Handling Method FA FWa FW FW FW/FD FW BA BW BW BW BW BW

Ash Disposal Method and Frequency CoD CoD CoD SD CoD FA int int int cont int BA int int int int int

Pyrite Handling Method No Current CoD CoD CoD Pyrites CoD Past CoD CoD CoD Reported CoD

Ash in Storage b 3 tons) (10 Flyash & Bottom Ash 2400 600 1800 400 1600

Remaining Life at Disposal Sites (years) 2 8 10 25 0.8

Bottom Ash Properties Gradation NA NA NA NA NA Max. Particle Size (inch) ? ? ? ? 0.2mm Coeff. of Uniformity NA NA NA NA 5.6 Specific Gravity NA NA NA NA 2.57

Disposal Costs c - 1981 (per ton) $3.89 $7.48 NA NA

Ash Sales - 1981 (10 3 tons) FA N N N 13 BA

Ash Agreements - expiration FA N N N 1990 1985 BA N N N N 1985

20 TABLE 2.2 FOOTNOTES

NOTATION USED:

FA - Fly Ash CoD - Codisposal BA - Bottom Ash SD - Separate Disposal FW - Wet Handling of Fly Ash cont - Continuous disposal FD - Dry Handling of Fly Ash int - Intermittent Disposal BW - Wet Handling of Bottom Ash NA - Information Not Available BD - Dry Handling of Bottom Ash N - None

(a) By mid-1983, Plant Crist will be utilizing a new ash disposal site, in which bottom ash and fly ash are collected and disposed of in a dry form; pyrite will be disposed of separately by routing to the old pond.

(b) Estimated quantities of ash in storage are the sum of ash produced during each year of the plant's life

gen. capacity on line Ash Produced = x 1981 ash production 1981 gen. capacity

No attempt was made to reduce these quantities by the amounts of ash which may have been sold (Note: 1981 system-wide ash production estimates indicate that bottom ash represents approximately 20 percent of total ash produced).

1981 O&M + 1981 Capital Expense (c) Disposal costs were computed, in general, as 1931 Ash Production In providing this information, however, the operating companies may have used different accounting procedures. As a result, cost comparisons should not be made on a company to company basis, but should be restricted to plant comparisons within a particular company. SUMMARY OF PYRITE HANDLING AT GEORGIA POWER COMPANY PLANTS

PLANT HANDLING METHOD

Arkwright Pyrites are pumped from the mill reject hoppers into the furnace ash pit. Material in the ash pit is pumped in a bottom ash line to the ash pond. Bowen (Units 1 & 2) The pyrites are sluiced from the mill reject hoppers into the pyrite holding tank. The pyrite holding tank is sluiced in a bottom ash line to the ash pond. Bowen (Units 3 & 4) (Past) - The pyrites were sluiced from the mill reject hoppers into a pyrite holding tank. The pyrite holding tank was emptied through a bottom ash line into the ash pond. (Present) - The pyrites are emptied from the pyrite holding tank into a top ash line and pumped to the ash pond. Bottom ash is collected pyrite-free in a separate collection basin. Branch (Present) - Pyrites are sluiced from the mill reject hoppers into the ash pit. Material in the ash pit is transported through a bottom ash line to an ash lift station. From the ash lift station the ash (top ash, bottom ash, and pyrites) can be pumped via common line to the ash pond. (Future) - Plans for Units 1 and 2 are to remove pyrites manually from the building. Bottom ash from these two units will be collected in a separate system (pyrite free) at the ash lift station. Hammond The system is very similar to Plant Arkwright's system. The pyrites are sluiced from the mill reject hoppers to the ash pit and then dumped through a bottom ash line to the ash pond. McDonough (Past) - Pyrites were pumped from the mill reject hoppers into the ash pit and from there through a bottom ash line to the ash pond. (Present) - Pyrites are removed manually from the mill reject hoppers and carried outside the plant on a conveyor belt. The conveyor system dumps into an open truck and the material is hauled to the No. 4 Ash Pond. Bottom ash is collected pyrite-free in a separate collection basin. (Continued)

McManus The pyrites from Units 1 and 2 are pumped from the mill reject hoppers into a pyrite holding tank. The pyrite holding tank empties into the No. 3 unit ash pit. Pyrites from the No. 3 unit are pumped from mill reject hoppers into the No. 3 ash pit. Material in the ash pit is pumped through a bottom ash line to the ash pond. Scherer Unknown Wansley Pyrites are pumped from the mill reject hoppers into a pyrite holding tank. The holding tank pumps to an ash lift station. All ash material in the lift station is pumped via common line to the ash pond. Yates (Units 1 - 5) The pyrites are sluiced from the mill reject hoppers into a pyrite holding tank. The pyrite holding tank dumps into the plant ash pit. Material in the ash pit is pumped through a bottom ash line to the ash pond. Yates (Units 6 - 7) The pyrites are sluiced from the mill reject hoppers into a pyrite holding tank. The pyrite holding tank is emptied through a separate line to a collection pond maintained separately from the active ash pond. The bottom ash is collected pyrite-free in a separate collection basin. bottom ash, with minimal mixing during removal from the ash pond, can attain a reasonably constant gradation. He did indicate that AEP often "wastes" bottom ash deposited in the far side of the pond from the outfall. Up to 20% passing the No. 200 sieve is commonly found in this region whereas about 8% is optimum

[44]. He did indicate, however, that the major consequence of the "finer" bottom ash is simply that it requires a slightly higher cement content for stabilization.

Rachford [57] reported that the gradational variations encountered in the bottom ash removed from one of the ponds at Plant Hammond was controlled by simultaneously feeding ash to the pugmill from two different stockpiles, one containing primarily coarse bottom ash and the other containing more of the finer fly ash. By adjusting feed rates from the two sources, a relatively consistent gradation was maintained for base course construction near the

Georgia Power Rocky Mountain project in northwest Georgia. (See Figure 2.2.)

2.2.2 Pyrite

Iron Pyrite (FeS 2 ) is found naturally in coal and typically comprises 1% to 7% by weight of the coal [39]. Although some of the pyrite may be found in microscopic form, a major portion exists in the form of discrete nodules which are larger than a No. 200 sieve and may be as large as 1 inch [39]. These nodules are exceedingly hard (Moh hardness 6-6.5), are not normally crushed by the ball mill, and are relatively heavy (specific gravity 4.8 to 5.2) [39].

Because of these characteristics, the pyrite is fairly easily removed at the pulverizer and does not get into the furnace. Any small fraction that does enter the furnace is oxidized.

Pyrite handling at power plants varies but typically this material is collected and disposed of along with the other ash materials. In some cases care is taken to maintain pyrite-free ash deposits by maintaining separate

24 , 100 .. ' ir 4: 4p , \

c.0'2. -3,..c.e. o hob. 80 -c> r 40-c. <'. 4''C'?- N.lk \tza.{\- 2° NN' e z 60 V'b. N` ,,,C\-.0 \ \Ns iP- h. \ ,r 4 j liw 0 • V 'N>, Al. V.- '41, 16c" N. , . ir

C0°.-C.5 -$0 sileP 20 .0( tCX1ell. VO . PA lki- 0 200 40 20 10 4 3/8" 3/4 1 1 SIEVE NUMBER

Figure 2.2. Typical Gradation Curves for Dry Bottom Ash from West Virginia and Georgia.

25 disposal sites for the pyrite and ash materials. Ratcliffe [71] indicates that for Georgia Power ponds where co-disposal has been used, pyrites should be less than 1% of ash pond deposits and are likely to be near the sluice pipe outfall points. Tables 2.2 and 2.3 summarize pyrite disposal methods at plants within the Southern electric system.

2.3 PRODUCTION OF BOTTOM ASH

The total ash (fly ash plus bottom ash) produced in the United States has been increasing each year and this trend is likely to continue in the future.

For example, in 1966 a total of about 23 million tons of ash was collected

[30]. By the year 1974 this had more than doubled to a total of 54 million

tons and by 1980 it was 68 million tons [46]. The National Ash Association

has projected that by 1985 the annual production rate will be 90 million tons,

increasing to 125 million tons per year by 1990 [45].

The Southern System annual production rate of ash (based on 1981 figures)

is about 4.3 million tons, including -0.8 million tons of bottom ash. Over 50

million tons of ash is estimated to be stored in ponds at various plants in

the Southern electric system. A breakdown by ash type, company and plant is

summarized in Table 2.2.

2.4 PROPERTIES OF BOTTOM ASH

The various physical, chemical and engineering properties of bottom ash

materials obviously are significant relative to the suitability for utiliza-

tion in various highway applications. The major variables that influence

these properties include [6]:

1. type of coal and variability of its composition

2. degree of pulverization

3. type of furnace

26 4. firing temperature and other operating parameters

5. characteristics and operation of ash collection and disposal system

6. environmental effects (e.g., leaching, weathering, self-hardening,

etc.)

7. time

Ash can be placed into four major categories according to the classes of coal from which it is derived [6]. The four classes according to rank are:

Class Name Source

I Anthracite (Ref. 6 included no information)

II Bituminous Appalachian Region & Illinois

III Subbituminous Rocky Mountains, Northern Great Plains (Wym., Mont., N. Mex., Alaska)

IV Lignite Texas, N. Dak., Montana

In general, as the coal source(s) changes, so will the nature and variability of the ashes [6]. A classification system based on the characteristics of the ash is badly needed. A system has been proposed by the Polish [47] but has not been used in the United States.

Table 2.1 summarizes the coal sources and general classification for the plants within the Southern system. The type of furnace and ash collection and handling techniques will exert a major influence on many of the characteristics of bottom ash.

2.4.1 Physical Properties

The physical properties of general interest include specific gravity, water absorption, gradation, color, and shape/surface texture.

Specific Gravity and Water Absorption

In general, boiler slag tends to have a greater specific gravity than dry bottom ash. However, because the specific gravities of ashes are a function

of the chemical constituents and porosity of the ash, ashes having high iron contents (Fe0 and Fe 0 ) will have correspondingly high specific gravities 2 3 and porous ash will have correspondingly lower specific gravities. Furthermore, the percentage of friable particles (sintered fly ash) or "popcorn" ash present will significantly affect the specific gravity. The following list summarizes typical specific gravity information.

Ash Source (Plant) Boiler Type Bulk Specific Gravity

Fort Martin (No. 1&2) dry bottom 2.41 Kammer wet bottom 2.72 Kanawha River Ref. 1 dry bottom 2.28 Mitchell dry bottom 2.78 Muskingham wet bottom 2.47 West Virginia, Ref. 44 dry bottom 2.15 Georgia, Ref. 56 dry bottom 2.25-2.45

It is interesting to note the low specific gravity value for the West

Virginia ash (Kinder, Ref. 44). (The significance of low specific gravity will be discussed later in this report.) The bottom ash in West Virginia has a very low iron content.

Majidzadeh, et al. [16] have also reported specific gravity and water absorption (ASTM C-127 and C-128) values for 32 ash samples (Table 2.4). The apparent specific gravity of the dry bottom ash ranged from 2.08 to 2.49 while water absorption ranged from 0.4 to 8.0% by weight. The porous nature of bottom ash presents some problems in determining specific gravity and water absorption for dry bottom ashes [43].

Grain Size

The grain size distribution of dry bottom ash can be influenced by several factors, including the furnace type and collection and handling techniques.

For example, the type and wear of the clinker grinder has an influence on the

28 TABLE 2.4 SUMMARY OF SPECIFIC GRAVITY AND WATER ABSORPTION TEST RESULTS FROM FHWA STUDY (Ref. 16)

Sample Type of Specific Water Absorption (%) Numbera Bottom Ash Gravity Fine Coarse Average

2 Dry& Wet 2.29 0.79 3.60 2.93 4 Dry 2.48 0.50 4.80 0.98 5 Dry 2.62 1.39 1.53 1.41 6 Dry 2.44 0.49 3.32 0.63 7 Dry 2.15 0.27 4.42 3.12 8 Dry 2.24 2.24 6.22 4.17 9 Dry 2.26 0.50 2.68 1.01 10 Dry 2.14 4.07 2.14 3.58 11 Dry 2.71 1.60 4.21 2.01 12 Dry 2.49 0.16 3.95 0.40 13 Wet 3.85 1.49 4.59 1.71 14 Dry 2.59 5.45 3.11 4.61 15 Wet 2.86 0.26 3.52 0.27 16 Wet 2.79 0.18 3.46 0.19 17 Dry 2.73 4.88 2.49 4.30 18 Wet 2.83 0.45 2.57 0.57 19 Wet 2.60 0.60 2.36 0.71 20 Dry 2.20 1.72 4.35 1.83 21 Dry 2.49 0.92 1.91 1.70 22 Dry 2.10 2.66 3.11 2.68 24 Dry 2.35 0.81 25.16 7.52 25 Dry 2.60 2.01 2.19 2.02 26 Dry 2.08 1.34 5.43 2.46 27 Dry 2.48 0.40 2.21 0.83 28 Wet 2.62 2.00 2.49 2.18 29 Dry 2.66 4.02 1.65 3.87 30 Wet 2.70 1.29 3.85 1.39 31 Dry 2.29 7.03 5.90 6.69 32 Wet 2.61 0.45 0.82 0.47

a See Table 2.6 for sample source identification. gradation. Additionally, for ash pond deposits the gradation will depend on location relative to the outfall pipe and whether fly ash was co-disposed.

Figure 2.2 depicts typical gradation curves for various bottom ash materials reported by Seals, et al. [1] and Webb [48]. The dry bottom ashes typically have coefficients of uniformity ranging from 5 to greater than 20.

Also of interest is the fact that some of the larger particles may consist of poorly sintered fly ash particles which are quite friable and may break down into smaller particles. Anderson [33] and Kinder [44] have reported this, although there is no information on the presence of such particles in Southern system bottom ashes.

Color

Typically the color of dry bottom ash is gray to black. Tan to gray color exists for ashes which have low iron contents; as the iron content increases, the predominent color becomes dark brown to black.

Shape and Surface Texture

The shape and surface texture of dry bottom ash differs somewhat from boiler slag. Boiler slag is commonly angular to subangular in shape, with a glassy although somewhat porous surface texture. In addition, some of the particles are rod shaped.

Dry bottom ashes have a very vessicular structure and as such have a porous surface, although some glassy particles are often present. The particles tend to be angular in shape.

2.4.2 Chemical Properties

The chemical composition of bottom ash is directly influenced by the coal composition and its constituent minerals. 80-90% of the total ash is composed of silica (Si0 2 ), ferric oxide (Fe 20 3 ) and alumina (Al 2 0 3 ). Figure 2.3 depicts

Variation in chemical constituents of fly ash in United States.

z az— AVERAGE til RANGE mu 40 u.■

z 30 0

..c!' 20 z 8 lo

Si 02 M 2 0 3 Fe20 3 CaO MgO 50 3 NO 2 0 OTHER LOSS ON IGNITION CONSTITUENT

Variation in chemical constituents of bottom ash and boiler slag in United States.

60 T

50 RCEN PE 40 ON .

ATI 30 TR

EN 20

CONC 10

0 Si 02 A I 203 F4203 COO MgO No20 SO 3 0 20 CONSTITUENT

Figure 2.3. Variations in Chemical Composition of Flyash and Bottom Ash (Ref. 30).

31 the variation in chemical composition of fly ash, bottom ash and boiler slag in the United States. Majidzadeh, et al. [2] present extensive results on chemical analyses of ash from almost 200 coals in the United States (Table

2.5).

The presence of pyrite in bottom ash is virtually impossible to detect with conventional chemical analysis techniques [56], although the presence of the pyrite can be detrimental to the performance of certain paving materials such as bituminous mixes. Anderson,et al. [33] also report that sulfates can precipitate in the furnace as complex soluble sulfate salts which can result from other than pyrite-contaminated ash. Ash contaminated with these sulfates exhibited expansive behavior when used in asphalt mixes.

2.4.3 Engineering Properties

The potential of bottom ash as an aggregate or paving material must be evaluated by the potential user. Often, test methods and specifications developed for use with conventional aggregates are applied indiscriminately.

Usmen, et al. [43] have presented strong evidence that many conventional test methods and specifications are not applicable to bottom ash. Their use with bottom ash is often misleading. Assessment on the basis of conventional tests and specifications may lead to approval of a questionable material or arbitrary rejection of a suitable material. This problem will be discussed in more detail later in this report. The following information discusses properties in terms of conventional engineering test methods.

Los Angeles Abrasion Test

(ASTM C-131)

The LA abrasion test is a widely used standard aggregate quality test and is generally believed to identify poor quality aggregate material being con-

32 ASH CHEMICAL ANALYSES FOR A LARGE NUMBER OF U.S. COALS (Ref. 2)

Percent of State, .County and Bed moisture - Analysis of ash, percent free coal Ash Sulfur SiO2 Al203 Fe201 TiO2 P205 Ca0 Mg0 Na20 K7 0 ALABAMA Jefferson: Clements 6.9 1.6 45.2 • 23.5 25.9 1.0 0.17 1.8 0.9 0.2 2.6 0.6 Marion: Black Creek 5.2 1.1 45.2 24.9 15.6 0.8 0.31 3.8 1.9 0.3 2.4 3.6 Shelby: Montevallo 7.3 0.8 35.4 19.8 17.9 0.6 0.06 12.4 2.4 0.2 0.2 7.4 Tuscaloosa: Milldale 5.3 1.0 48.2 28.2 15.1 1.4 0.13 1.8 0.8 0.3 1.2 2.4 Walker: Black Creek 5.5 2.8 23.9 18.4 45.0 0.8 0.13 3.4 0.8 0.3 0.9 4.7

ARKANSAS Johnson: Lower Hartshorn 3 4.0 --- 25.2 27.4 20.3 1.3 1.3 7.4 4.4 2.1 1.2 10.3 Logan: Paris 12.5 2.5 24.4 12.1 26.5 0.6 0.82 18.8 5.4 0.8 1.3 10.0

COLORADO • Fremont: Unknown 15.9 0.4 53.9 23.4 5.3 1.1 0.01 8.5 0.9 0.4 0.2 6.6 La Plata: Unknown 5.2 1.1 47.7 30.9 11.9 1.4 0.13 5.3 0.6 0.4 0.2 1.8 Las Animas: Unknown 9.2 0.6 48.2 28.2 8.7 1.4 2.8 4.8 1.6 0.3 0.2 2. 4 Mesa: Unknown 13.2 0.9 50.0 33.3 4.1 1.2 :0.43 5.9 0.5 1.8 0.6 1.6 Moffat: Unknown 3.0 0.4 34.8 22.7 6.0 1.7 0.38 12.8 2.0 3.0 0.3 15.1 Montrose: Unknown 11.9 0.9 56.6 34.2 5.1 1.6 0.02 1.8 0.6 0.2 0.8 0.8 Routt: Wadge 8.5 0.8 48.4 30.6 4.7 1.2 1.5 4.6 1.5 0.2 0.6 4.8

ILLINOIS Fulton: Number 5 10.6 3.3 51.7 15.7 16.3 0.6 0.06 8.9 0.8 0.5 2.0 2.8 Henry: Number 6 7.7 3.2 41.4 20.4 23.3 1.5 0.06 6.8 1.3 0.5 2.1 2. 4 Jackson: Number 6 8.3 2.4 49.3 22.3 19.5 1.2 0.06 1.7 0.8 0.4 2.2 1.0 (Continued)

Percent of State, County and Bed moisture - - , Analysis of ash, percent . free coal . Ash Sulfur SiO2 Al203 Fe2OR TiO2 P205 CaO MgO Na20 _KO SO3 ILLINOIS (continued) • Kankakee: Numbers 2&5 6.5. 2.7 36.0 20.5 35.4 1.0 0,11 1.8 0.8 0.6 1.8 1.2 Peoria: Number 6 8,1 3,0 42.7 23.2 23.9 0.7 0,11 3.4 0.9 0.3 2.3 0.8 Randolph: Number 6 17.1 4.8 46.6 19.3 20.8 0.8 0.24 7.7 0.9 0.2 1.7 2.4 Saline: Davis 12.7 4.5 42.5 18.5 34.8 0.9 0.20 1.7 0.4 0.1 1.8 1.0 Schuyler: Number 5 10.3 3.6 48.0 14.7 18.7 0.6 0.44 10.4 0.6 0.2 1.8 2.1 Stark: Number 6 8.9 3.1 42.1 20.1 22.8 1.1 0.15 6.6 1.1 0.5 1.9 2.0 Vermilion: Number 7 9.1 3.0 45.8 20.2 20.0 1.0 0.03 6.1 1.3 0.6 2.3 2.2 Williamson: Davis 11.2 3.2 54.5 15.4 21.1 1.0 0.27 1.7 0.9 0.2 2.6 1.1 - INDIANA Clay: Number III 7.2 4.0 36.4 20.3 31.8 0.8 0.22 6.1 0.6 0.3 1.5 1.8 .Greene: Number V 8.7 2.8 51.7 25.3 15.9 1.2 0.03 1.8 1.0 0.3 2.4 0.6 Knox: Number V 9.2 3.4 47.6 23.6 15,5 1.1 0.10 3.2 0.8 0.9 2.9 1.0 Owen: Upper Block 7.6 2.6 51.9 25.4 17.5 1.2 0.27 1.8 0.7 0.2 1.7 0.4 Pike: Number V 9.1 3,1 42.9 22.3 29,3 1.1 0.18 1.9 0.6 0.2 2.0 0.6 Sullivan: Number VII 9.7 0.7 60.9 25.4 7.0 1.3 0.02 1.8 1.5 0,3 3.1 0,2 Vigo: Number VI 10.0 4.4 30.7 16.1 40.7 0.8 0.07 7.9 0.5 0.2 1.3 1.9 Warrick: Number V 12.4 4.2 35.4 18.6 27.7 1.0 0.06 8.4 0.6 0.4 2.4 3.1 IOWA Appanoose: Mystic 10.8 5.0 29.0 12.1 32.5 0.8 0.02 15.0 1.6 0.8 1.2 3.7 Marion: Unknown 16.0 5.3 39.6 15.8 34.3 0.9 0.56 4.3 0.9 0.2 1.2 2.4 (Continued)

Percent of , State, .County and Bed moisture - Analysis of ash, percent • . free coal • Ash Sulfur SiO Al 0 Fe2O TiO P2O Ca0 Mg0 2 2 3 3 2 5 Na2O K9 0 SO3 KANSAS Cherokee: Fleming and . Mineral 9.2 3.3 40.5 14.2 25.0 0.6 O. 05 11.7 0.8 0.,4 1.6 4. 0 Crawford: Weir-Pittsburg 11. 7 4. .7 35. 9 18. 5 40. 5 0.7 0. 27 1. 8 0. 3 0. 2 0.4 1. 4

KENTUCKY Bell: Hazard Nbr. 4 5.8 0. 9 46.9 28.4 12.0 1.2 0.24 2.7 2.0 0.2 2. 0 4.5 Hopkins: Number 12 15. 6 3. 1 57.9 18.8 11.3 1. 0 O. 13 5. 1 1.2 0.3 2. 8 1.7 Knott: Hazard Nbr. 4 8.6 0. 8 56.3. 32.6 4.5 1. 0 0. 05 1.7 1.5 0.5 1. 6 0. 9 Letcher: Hazard Nbr. 4 4.5 O. 8 47.9 32.9 9.8 1.4 0.10 1.8 0. 8 1. 8 1.4 2. 1 Martin: P.tmd Creek 8.4 1. 1 53.1 29.1 9.1 1. 8 0. 08 1.8 0.6 0.4 2.2 1. 8 Muhlenburg: Number 11 6.8 3.3 39.3 20.6 31.3 1.1 0.17 2.5 0.5 0.3 2.3 1.2 'Ohio: Number 9 8. 3 3.5 49.3 19.4 27.4 1. 0 0.03 1.8 0.7 0.2 1.9 0.2 Perry: Hazard Nbr. 9 9. 5 2.7 46.7 28. 8 19.1 1,2 O. 19 1.7 0.3 0.2 1. 0 1. 0 Pike: Elkhorn Number 1 8. 3 0.8 52. 0 34. 5 6.4 1.8 0. 11 1. 9 0. 6 0. 5 3. 3 0. 8 Union: Number 9 9.5 3.2 50.3 20.6 18.9 1.0 0.14 2.0 0.8 0.7 3.2 2.0 Webster: Number 14 9. 0 2. 9 42.4 22. 4 30.4 0.8 O. 13 1. 9 0. 9 0.2 1. 8 0. 9

MARYLAND Allegany: Pittsburgh and Tyson 10.4 0.9 57.1 31.6 4.7 1.6 0.37 2.0 0.5 0.9 2.6 0.4 Garrett: Upper and Lower Kittanning 8.6 1.7 46.2 29.1 16.4 1.2 0.05 1.7 0.8 0.3 2.5 1.3 Percent of , State, County and Bed moisture - Analysis of ash, percent free coal Ash Sulfur SiO2 Al203 Fe20 1 TiO2 P2O5 Ca0 Mg0 Na2O K90 SO3 MISSOURI Henry: Tebo - 11. 8 - 4.7 45.4 • 15.6 26.7 0.7 0. 14 6.2 0. 6 0. 1 1.7 3. 0 Macon: Bevier 10.1 5.2 37.9 16.3 41.0 0.6 0.02 1.7 0.4 0.1 1.3 1.1 St. Clair: Tebo 12, 8 4.3 43.6 14, 5 25, 8 0.7 O. 14 7. 0 0.8 0. 2 3. 0 3. 5 Vernon: Mineral 12. 2 4.2 41, 9 16. 8 30.7 0.8 0. 11 4.7 0. 8 0. 2 2, 3 2. 2 MONTANA Big Horn: Unknown 4. 2 0. 4 22, 1 15, 5 6.4 1. 2 O. 11 18. 9 6. 6 1. 0 0.4 26. 2 Dawson: Unknown 16. 9 0. 6 30. 0 25, 3 2. 9 0. 6 0. 76 11.7 4, 9 8. 1 0.4 12. 6 Garfield: Unknown 16. 8 0. 6 43. 2 23.7 4, 7 0. 8 0. 05 10. 0 2, 8 2. 0 1, 8 9. 0 Park: Unknown 13. 6 0. 5 53. 6 31, 9 5. 8 1, 0 0. 02 1. 8 1, 4 0. 8 0. 3 2, 4 Richland: Unknown 10. 0 0. 5 21. 9 13. 8 5. 9 0.7 0. 46 31, 4 10. 4 0. 3 0.3 12. 6

NEW MEXICO Colfax: Yankee 12, 6 0. 6 57. 4 30. 0 6.7 1, 2 0. 07 1.7 2, 0 O. 1 1. 0 0, 5 McKinley: Aztec 16. 3 1. 1 61. 9 22. 9 7. 8 0. 8 0. 01 3. 2 1, 5 0. 7 1, 1 2, 1 Rio Arriba: Unknown 10, 9 3.2 47.2 20.4 27. 3 1, 0 0. 06 4, 3 0. 8 0. 3 0.2 0. 6 Sandoval: Kaseman 5, 9 1. 5 28. 9 14, 3 22. 1 0. 9 O. 12 11.2 4, 2 0. 5 0. 2 17. 3 San Juan: Unknown 2. 9 0.7 42, 8 22, 3 15, 2 1.3 0. 08 3.9 2, 7 2, 2 0.1 6, 0 Socorro: Carthage 14. 6 0. 8 56, 7 21, 0 3. 6 1. 1 0. 02 14.0 0. 8 0. 2 0. 9 1. 6 (Continued)

Percent of , State, County and Bed moisture - • Analysis of ash, percent • . free coal • Ash Sulfur SiO Al203 Fe20 1 TiO2 P205 CaO MgO 2 Na20 K70 SO3 NORTH DAKOTA Bowman: Unknown 16. 9 - 1. 5 40.4 10. 6 4. 1 • 0. 9 0. 04 14.7 5. 4 2. 5 0.2 20. 3 Burke: Unknown 12.6 1. 0 31.2 16, 8 6. 0 0. 9 0. 04 14.5 3, 3 7. 3 0.2 19. 2 Mercer: Zap 12. 1 1. 1 23. 8 10. 5 10. 1 0. 6 0.27 16. 6 5. 1 8. 2 0.6 23. 5 Ward: Coteau 7.5 0. 5 15. 0 13. 0 6. 1 0.7 0.37 36. 0 10. 8 0.9 0.3 16. 6 OHIO Belmont: Pittsburg (#8) 10. 8 4. 3 42.4 19. 6 27. 5 0. 9 0. 15 4. 8 1. 2 0.2 1. 6 2, 0 Carroll: Lower Freeport 12. 0 2.4 47.2 26. 6 21, 4 1. 3 0. 27 1. 9 1. 0 0.2 1.7 0. 7 Columbiana: Middle Kittan- ning (#6) 9. 4 3. 9 30. 2 21.2 45. 2 0. 8 O. 19 1, 8 0.7 0. 2 1, 0 0. 8 Coshocton:, Middle Kittan- • ning (#6) 5.9 3.2 31. 6 . 21.3 40.7 0. 9 0. 08 1. 8 0.6 0.2 1.2 1. 8 Gallia: Lower Kittanning 17. 1 4. 9 34. 6 28.9 33. 2 0. 8 0. 21 1, 7 0. 2 0. 1 1. 0 0. 7 Guernsey: Anderson 11.7 3. 1 48.9 22.4 19.0 1.4 0.55 3.1 1.1 O. 3 1.6 2. 0 Harrison: Sewickley (#9) 13.7 2. 6 53.1 26.4 18.7 1. 1 0. 17 0. 4 0. 8 0. 3 2, 0 0, 3 Jefferson: Harlem 11.2 2.2 53. 1 20. 9 19.2 0. 9 0. 24 1.7 1. 0 0. 3 2.7 0. 8 Lawrence: Lower Kittannirg 4. 6 1, 7 33.1 29.6 30.6 0. 6 0.25 1. 8 0. 3 0.3 0.4 2. 6 Mahoning: Brookville (#4) 14.7 6. 3 34.3 18.1 39.7 2.2 0. 09 1.8 0.2 0.2 1, 2 1, 6 Meigs: Redstone (#8A) 8.7 1.2 56.1 30.2 8.7 1.4 0.24 1. 8 0. 6 0. 6 1. 6 0. 6 Morgan: Sewickley (#9) 16.7 4.5 46.0 20.3 24, 6 0.8 0.30 1. 8 1, 5 1. 6 1.9 1. 8 Noble: Sewickley (#9) 17. 2 6. 9 36.7 19. 9 37. 8 0. 8 0. 23 1. 8 0. 6 0. 6 1.4 0. 7 Perry: Lower Kittanning 12. 9 4. 3 31. 8 23. 9 39. 5 0. 6 0. 52 1. 8 0. 3 0. 3 0. 9 0. 4 Stark: Middle Kittanning 14. 9 5. 1 39. 9 22. 0 34. 8 0. 8 0.11 1, 9 0. 7 0. 7 1, 8 1. 1 Tuscarawas: Mid. Kittan. 8. 0 4, 1 32. 2 20.7 • 43. 2 0. 9 0. 06 1. 9 0. 7 0.7 0.5 2. 1 (Continued)

Percent of , State, County and Bed moisture - . Analysis of ash, percent free coal Ash Sulfur 5102 Al203 Fe2O3 TiO2 P2O5 CaO MgO Na2O K70 SO3 OHIO (continued) Washington: Sewickley (#9) 12.2 5. 7 40. 0 • 20. 2 35.2 0. 8 . 06 1.8 0.4 0. 3 1.5 0.7 PENNSYLVANIA Allegheny: Pittsburgh 7, 9 2. 0 49.2 24. 8 20. 3 1. 0 . 14 1. 8 0.5 0.2 3. 6 1. 3 Armstrong: Upper Freepor; 10.0 1. 7 50. 5 27.4 16. 8 1.1 . 32 1. 8 0. 9 0.2 2.5 1, 0 Beaver: Lower Kittanning 6.7 1, 4 42. 3 32.7 15. 4 0. 9 1. 2 2. 0 0. 3 0. 2 1.2 1, 6 Bedford: Lower Kittanning 10, 2 0.7 57.7 32.1 5. 1 1.7 .18 1, 7 0. 9 0.2 2.6 0.2 Butler: Upper Freeport 12, 4 2, 8 44, 9 24.7 23, 1 1. 8 . 54 2, 2 0. 6 0. 3 3.4 0. 8 Cambria: Lower Kittanning 8. 7 2. 3 37. 4 26. 3 33. 3 1. 1 . 11 1. 8 0. 4 O. 1 1. 0 1. 6 Clarion: Clarion 9. 9 4. 5 32, 7 20.-9 43. 3 1. 0 . 28 1.4 0. 2 O. 1 0. 8 1.4 Clearfield: Lower Freeport 9. 2 3. 5 36. 5 21. 2 38. 2 0.7 .20 1. 7 0. 3 0. 2 1. 0 1, 1 Elk: Clarion 9.7 2.3 42, 1 24.3 24.6 1.3 . 12 1, 8 0. 3 0. 2 1, 0 2. 0 Fayette: Pittsburgh 9. 2 3. 5 49. 8 25. 2 16, 0 1. 1 . 24 3. 3 0. 7 0. 4 1, 7 1, 9 Indiana: Lower Kittanning 8. 9 1, 3 49, 3 30.7 11. 9 0. 9 .18 1. 7 0. 5 0. 2 1. 8 1, 6 Jefferson: Lower Kittan'ng 7, 6 1, 1 47. 5 30, 8 9, 3 1. 6 2. 9 3. 6 0. 4 O. 1 1. 1 1. 5 Lawrence: Brookville 10. 3 2, 4 43. 4 25, 6 24. 2 1, 6 1.2 1. 9 0, 3 0. 2 1, 1 0.2 Mercer: Brookville 5, 7 1. 2 34, 0 28. 7 25, 3 1.4 . 60 5. 3 O. 7 0. 4 1.2 2. 7 Somerset: Lower Kittan'ng 8. 0 2. 3 35, 1 28. 7 31. 4 1. 0 . 11 1. 8 0. 3 0. 2 0. 6 2, 1 Washington: Pittsburgh 9. 8 1. 1 47. 6 25, 8 9, 6 1. 1 . 23 9. 1 1. 4 0, 5 1.5 3. 0 Westmoreland: Pittsburgh 8. 1 1. 0 54.0 29.3 7. 8 1.3 .14 2.7 0. 9 0.4 1, 9 1, 4

TENNESSEE . Anderson: Dean 16.5 3. 8 45, 4 25.2 19. 9 1. 0 . 36 - 1. 7 • 1. 6 0. 5 2, 9 1.6 Campbell: Dean 13.9 3. 5 44. 3 23. 7 19. 5 1.7 . 73 1. 8 0.7 0. 2 2. 0 2. 1 TABLE 2.5

(Continued)

Percent of , State, .County and Bed moisture - • Analysis of ash, percent

. free coal . Ash Sulfur SiO Al 0 Fe 2 2 3 203 TiO2 P20 5 Ca0 Mg0 Na20 K90 SO3 TENNESSEE (continued) Claiborne: Jellico 4.8 0.9 49.4 32.7 9.5 1.7 . 57 1. 8 0.7 0.5 2. 0 1. 5 Claiborne: Mason 10.7 1. 8 46.4 27.4 17.2 0.9 . 13 1.7 1. 5 0.3 4.7 0. 8 Grundy: Sewanee 9.6 0.9 56.5 25.8 7.3 1.0 1.1 1.7 1.5 0.2 3.1 1.1 Marion: Sewanee 10. 0 0. 6 55. 0 25. 9 6.1 1. 0 1. 6 2. 8 1. 5 0. 2 2.7 1. 8 Morgan: Glen Mary 6. 1 2. 0 44. 3 28.8 20.2 1. 3 .41 1. 8 1.2 0.2 2.9 1. 2 Scott: Glen Mary 9. 6 3. 9 33. 6 18. 6 41. 6 1. 0 . 14 2. 3 0. 9 0. 4 1. 0 3. 0 Sequatchia: Sewanee 11.8 1. 0 53.1 26.3 7.6 1. 0 1. 8 1.7 1. 3 0.2 3.3 1. 0 UTAH Carbon: Castlegate D 8. 1 0. 4 50. 5 10. 3 4. 9 0.9 . 62 17. 2 7. 6 0. 4 0.4 6. 6 Carbon: Rock Canyon 8. 0 2.2 51.1 19.8 19.3 0.8 1.4 3. 5 0. 3 0.5 0.7 1.8 .Emery: Ferron A 6. 3 0. 5 46.7 19. 2 8. 0 1.3 . 80 10. 9 4. 5 1. 5 0. 2 6. 8 Sevier: Hiawatha 6.9 0.4 46.4 9.1 7. 0 0. 6 . 03 21. 9 3. 6 1. 0 0. 1 7. 5 VIRGINIA Buchanan: Hagy 6.3 1. 0 54.8 28.6 11.4 1.5 . 11 1.0 0. 8 1. 1 1.9 0. 8 Buchanan: Kennedy 7.7 1. 1 43. 6 31. 6 15. 6 1. 1 . 14 1. 9 1. 8 0. 5 4. 6 1. 3 Buchanan: Raven 6.0 1.2 45.1 26.7 19.1 0.6 .11 1.8 .1. 9 0.5 2.8 0.9 Dickenson: Hagy 8.8 1.8 48.1 27.9 19.6 1.9 . 10 1.8 0. 9 0.5 2.3 0.7 Dickenson: Lower Banner 6.3 0.8 37.0 22.4 11.2 1.4 . 18 14. 0 4.4 1. 3 0.3 7. 0 Montgomery: Brushy Mour- tain 31.7 0.7 64.0 25.7 4.5 2.1 . 07 1.8 0.5 0.2 1. 0 1. 0 Russell: Jawbone 14. 0 0. 6 48. 1 23.4 6.5 1.4 . 28 10.5 2. 6 0.7 1. 1 2. 8 Wise: Imboden 8. 3 2.2 46. 4 25. 5 24.1 1.2 . 47 1.2 0. 9 0. 4 2. 3 0. 6 TABLE 2.5

(Continued)

Percent of • State, .County and Bed moisture - • Analysi of ash, percent

. free coal Ash Sulfur SiO2 Al203 Fe20,1 TiO2 P 2 Mg0 Na20 K90 SO3 WASHINGTON

King: Black Knight 9. 5. 0.5 38. 8 0 CD 29.7 5. 3 1.2 1. 7 7. 6 C 10. 5

Pierce: Number 3 11. 2 O 0. 5 45. 8 • 31. 7 9. 2 2. 9 1. 6 1. 8 2. 7 WEST VIRGINIA ' . ,- Barbour: Lower Kittan'ng e- 10. 6 1 • 2.9 37. 8 27. 3 31.1 1.4 O. 11 1.1 I CD 1. 2 Barbour: Pittsburgh O 9. 0 4.5 31. 0 • 20. 8 35. 2 0. 9 O. 10 6. 9 C 3. 9 1-1

Barbour: Redstone D 7.1 1.5 47.2 • 30.1 15.7 1.2 1 7 2. 1 1.8 ri Barbour: Upper Freeport 1- • 16.2 3.0 35.4 1 00 17.9 43.7 0.8 1 1 1. 0 1.1 Boone: Alma 0 8.5 3.2 36.4 • 21.8 34.8 1.0 O. 08 1. 9 C 2.3 CV Boone: D Campbell Creek 11.6 0.6 52.4 •

27.7 11. 8 1.7 C 10 0. 9 M 0.9 Boone: CV Cedar Grove 3.3 0.8 • 45.1 35.8 7.7 1.3 O. 07 1. 9 C' 2.6 1-1 1-1 O O

Boone: D Coalburg • 14.3 • 0.9 54.0 34.5 5.2 1.5 O. 51 1. 9 V 0.6 N

Boone: Winifrede D 13. 0 0. 8 • 58. 1 C 31. 8 3. 8 1.7 O. 05 O. 9 0. 7 D

Braxton: Pittsburgh 5.9 1.1 • 38.1 25.7 19.7 0.9 C 8.7 Cr 3.3 1-1 ) Cr) Clay: Lower Kittanning 7. 1 • 0.7 52. 3 32. 6 5. 7 3.3 O. 06 1. 8 1. 3 CV

Fayette: Campbell Creek 6. 3 0.8 . 48. 5 30. 1 13. 6 1. 1 C 07 1. 8 1. 3 CV CV 4

Fayette: Lower Eagle 6.0 . 0.9 53.1 31.3 9.9 1.1 C 1. 8 0.8 • --4 :1 , Gilmer: Pittsburgh 7.7 • 2.0 35.6 22.8 24.5 1.2 O. 27 9. 5 CV 3.4 C0

Greenbrier: Sewell 4. 6 • 1. 0 47. 1 00 28. 2 15. 8 1. 1 0. 20 1. 9 1. 5 c)

Harrison: Pittsburgh 9. 9 •

4.7 26.5 22. 0 47. 8 0. 8 0. 23 1.7 2. 8 O CT ) 0 Harrison: Redstone 7. 8 3. 8 23. 8 17. 9 39. 1 0. 6 0. 38 12. 7 • 4. 0 c

Kanawha: Campbell Creek 4. 5 0. 8 • 39.7 25. 8 10. 9 1.2 3. 0 8. 5 5. 9 t- - Kanawha: Cedar Grove 5. 3 0. 9 50. 2 33. 0 9. 1 1.4 0. 13 , 1. 8 • • 1. 9 TABLE 2.5 (Continued)

Percent of State, County and Bed moisture- free coal Ash Sulfur SiO2 A102 Fe2( TiO Ca0 Mg0 Na2O K90 SO. WEST VIRGINIA (Cont'd)

Kanawha: Co;lburg 12.2- 0 C7 57.9 34. 0 3. . r- Kanawha: Eagle 4.9 ri 54.4 31.8 7. I •i r-i Kanawha: Pit 7.0 41.1 •14 23. 1 28. Kanawha: Stockton-Lewiston 8.1 1-4 47.8 36. 0 5. •

Kanawha: Wii 3.6 49.3 36. 4 CO 5. CV N - Lewis: Pittsburgh :14

9.4 35. 0 • 18. 9 35. 07 Lewis: Redstone 8. 6 30.5 19. 4 • 39. Logan: Camp' 1-4 0 Creek 7.9 58.2 30. 0 • 3. Logan: Chilton c 13.9 57.1 • 38. 2 3. 0 Logan: Lower Kittanning 9. 5 64. 5 29. 0 2. I• I. c Marion: Sewickley 11.7 41.7 L—

23. 6 19. 0" 1-1 18. C:) Cs C O O L— ) Mason: •

Pittsburgh •

14. 9 43. 9 27.. 3 . .

McDowell: co Pocohantas 3 6.7 48.5 29. 1 • 10. Mingo: Cedar Grove CD 3.4 4.

49.2 CD 30. 8 8. Monongalia: Lo Pittsburgh 9.0 •

36.1 24. 4 6 0' 26.

Monongalia: Waynesburg 14. 5 51. 0 ) 27. 3 16. Nicholas: co Campbell Creek 4.9 •

40.8 29. 7 16. Nicholas: Coalburg " 6. 8 • 50. 3 35. 4 5. c' O

Nicholas: Lower Kittan'ng 4. 8 •

46. 3 32. 1 12. 2 0. 05 Nicholas: cn ' Sewell 3.7 52.5 31.4 • 6.5 0.25 1 ' a Pocohontas: Sewell 4. 9 42. 0 • 37. 2 10. 6 1. 1 1-

Preston: , Bakerstown 10. 6 1 C> •

34. 4 19. 2 a 42. 0 0. 06

Preston: Mahoning , 17.4 52.4 • ca 29.8 10.5 0.11 Preston: Upper Kittan'ng 9. 3 40. 3 26. 0 27. 9 0. 39 TABLE 2.5

(Continued)

Percent of State, County and Bed moisture- Analysis of ash, percent free coal Ash Sulfur SiO2 Al2O3 Fe20 1 TiO2 P 2O5 Ca0 Mg0 Na2O 1(70 SO3 WEST VIRGINIA (Cont'd) Putnam: Pittsburgh 7.7 1.9 46. 6 ' 24.7 21.2 1.3 0. 62 1.7 0. 6 0. 3 1. 4 2. 6 Raleigh: Eagle 7.4 1.5 51.4 27.1 13.6 1.7 0.37 1.8 0.6 0.6 1.7 1.4 Randolph: Campbell Creek 2. 1 0. 9 23.4 27. 1 24. 9 1. 1 0.44 7.2 1. 8 1. 1 1. 0 9. 6 Randolph: Sewell 3. 9 0. 7 44. 7 36. 2 7. 6 1.5 0. 12 1. 9 0. 9 1. 0 1. 9 3. 5 Tucker: Upper Freeport 10. 6 2. 8 39.2 26. 3 31. 1 1. 1 0. 24 1.7 0. 4 0.2 1.4 1. 1 Upshur: Redstone 6. 2 1. 5 36. 5 25. 2 20. 9 0. 9 1. 1 7.9 1. 2 0. 3 1. 8 5. 6 Upshur: Upper Freeport 12.2 1.2 48.2 30.3 11.2 1.3 1.7 1.8 0.6 0.2 2.3 1.9 Webster: Fire Creek 8. 0 0. 5 54. 9 36. 9 3. 8 1.7 0. 14 1. 8 0. 2 0.1 0. 2 0.7 Wyoming: Beckley 7. 5 0. 8 51.3 33.0 6, 1 2. 0 1. 5 1. 9 0.4 1.3 1.3 0. 6 Wyoming: Powellton 6. 5 0. 7 57.7 27. 3 6. 2 0. 9 0. 07 1.7 1. 6 1. 0 3. 0 1. 2

WYOMING Carbon: Unknown 6. 4 0. 6 24. 5 14. 2 9. 0 0.9 0.21 30. 8 4.7 0.1 0. 5 14. 4 Carbon: Unknown 14.4 1.8 18.6 19.6 10. 3 1.8 0.51 9.4 4.4 0.2 0.6 16. 1 sidered for use in road construction. Many states and government specifications require that aggregates have LA abrasion values less than 40 to 50.

Data presented in References [1,33,43] (which is primarily for West Virginia bottom ash) and Majidzadeh, et al. [16] (for 32 bottom ash samples collected from 21 power companies in 14 states) generally ranges from 30 to 50 percent.

Table 2.6 presents the test results from Ref. 16. Note that only 2 of the ash samples had LA abrasion values greater than 50. However, Usmen, et al. [43] have suggested that LA abrasion may not be a good test for evaluating the quality of bottom ash.

Soundness Loss

(ASTM C-88)

To determine the resistance of an aggregate to disintegration and to help assess soundness of aggregate subjected to weathering, a sodium or magnesium sulfate soundness test is conducted. This test is recommended or required by most highway departments. Despite criticism of the test method [43], state

DOT specifications commonly require soundness values of less than 10-20 for aggregate acceptance [2].

Ref. 1 presents data showing that soundness loss for the bottom ash samples tested was always less than 20%. Majidzadeh, et al. [16] conducted soundness tests on both fine and coarse fractions of 32 bottom ash samples and found only two ashes which had a soundness loss greater than 10%, Table 2.6.

Again, Usmen, et al. [43] have discussed in detail the general inadequacy of this test for evaluation of bottom ash quality.

43 LOS ANGELES ABRASION AND SOUNDNESS TEST RESULTS FROM FM STUDY ( Ref. 16)

Sample Type of Los Angeles Soundness Loss (%) Source Number Bottom Ash Abrasion co) Fine Coarse Average

Ohio Edison Power Co. 2 Dry & Wet 49.5 1.12 4.98 4.08 Ohio Edison Power Co. 4 Dry 30.1 2.06 5.41 2.44 Ohio Edison Power Co. 5 Dry 34.1 2.74 4.16 3.02 Ohio Edison Power Co. 6 Dry 32.7 8.72 6.81 8.62 Ohio Edison Power Co. 7 Dry 49.6 4.80 6.47 5.95 Ohio Edison Power Co. 8 Dry 50.0 3.66 8.71 5.90 Monongahela Power Co. 9 Dry 45.3 2.55 5.34 3.21 Monongahela Power Co. 10 Dry 44.4 23.33 41.69 27.92 Monongahela Power Co. 11 Dry 37.2 7.97 7.49 7.89 Ohio Electric Co., Gallipolis 12 Dry 43.6 2.77 5.95 2.97 Monongahela Power Co. 13 Wet 46.8 8.66 13.41 9.00 Montana Power Co., Billings 14 Dry 33.9 6.66 10.68 8.09

Minnkota Power Co-op, N.D. 15 Wet - a - 1.31 - b - 1.34

Minnkota Power Co-op, N.D. 16 Wet - a - 0.71 - b - 0.71 Basin Electric Power Co - op 17 Dry 37.9 8.61 14.82 10.10 Black Hills Power & Electric, S.D. 18 Dry 51.5 3.05 8.77 3,42

Union Electric Co., St. Louis 19 Dry 38.0 3.73 - b - 3.67

Arizona Public Service Co. 20 Dry - a - 5.55 - b - 5.52 Minnesota Power & Light Co. 21 Dry 38.3 2.15 3.42 3.15

Southern California Edison Co. 22 Dry - a - 2.99 - b - 2.94 Public Service Co. of Colorado 24 Dry 78.7 4.05 6.89 4.83 Industrial Generating Co. 25 Dry 39.7 1.50 -b- 1.48 Pacific Power & Light Co. 26 Dry 43.3 5.50 5.40 5.47 Columbus & Southern Electric Co. 27 Dry 47.0 2.30 2.76 2.41 Chicago Flyash Company 28 Wet 43.4 4.44 -b- 4.35 Chicago Flyash Company 29 Dry 27.0 9.25 2.36 6.68

Columbus & Southern Electric Co. 30 Wet , 24.0 5.97 b - 5.92 Power Plant Aggregates of Iowa 31 Dry 35.0 8.90 3.06 7.16

Power Plant Aggregates of Iowa 32 Wet 31.4 6.41 - b - 6.33

Note: -a- denotes samples with less than 8 percent coarser than #8 U.S. sieve -b- denotes percent of fines greater than 98.00% Moisture-Density Relations

(ASTM D-698)

The compaction characteristic of bottom ash apparently is similar to that of many sands. West Virginia data [1] suggests that the dry bottom ash has a

relatively high optimum moisture content (compared to commercial aggregate of

similar gradation) due to the greater absorption characteristic. The West

Virginia results [1] showed X d max values (ASTM D-698) to range from 73 to

102 pcf while optimum compaction moisture ranged from 14 to 26%. Majidzadeh,

et al. [16] reported optimum moisture contents ranging from 13 to 18% for the

32 ash samples tested. Webb [48] reported maximum laboratory dry density

ranging from 88 to 122 pcf with optimum moisture contents ranging from 9.5%

to 17.4% for bottom ash samples from four Georgia Power plants (Arkwright,

Bowen, Wansley, Harllee Branch).

Density and Void Ratio

Density and void ratio characteristics of bottom ash materials differ

from conventional sand. Majidzadeh, et al. [16] reported test results based

on ASTM C29 (density) and ASTM C30 (void ratio). Significant variations were

noted from source to source, with bottom ash exhibiting greater variation than

boiler slag. Compared to a conventional sand like Ottawa, most bottom ash

yielded lower densities but considerably higher void ratios. Particle shape,

surface characteristics and chemical composition may have significant influence

on aggregate mixture density.

Angle of Internal Friction

Direct shear tests have been conducted to evaluate the angle of internal

friction. Values reported in literature range from 32° to 48° [1,16]. Angles in

general average 6° to 10° higher in a dense state compared to a loose state [2].

45 Degradation

Usmen, et al. [43] report that because of the inherently low particle strength of bottom ash, considerable degradation may take place under both laboratory and field compaction. Drop hammer compaction for preparation of bituminous mixtures and moisture-density tests can produce degradation.

Figure 2.4 depicts results of extracted gradations for two bituminous mixtures prepared by drop-hammer compaction. No quantitative information was found concerning the relative amount of degradation which may occur under various field use conditions. Clearly, there is potential for mechanical degradation in bottom ash; however, a dense gradation and proper confinement will reduce this effect. Blending of the bottom ash with commercial aggregates can also reduce potential for degradation. In cement or lime stabilized bottom ash mixtures, some degradation during construction should not have a significant effect on the quality of the resulting paving layer.

2.5 DISCUSSION

Large quantities of ash are produced at Southern system power plants, with as much as 0.8 million tons of the coarse bottom ash produced annually.

In addition, as shown in Table 2.2, it is estimated that approximately 50 million tons of ash currently is being stored in ash ponds at the various plant sites. As shown in Figure 1.2 some of the bottom ash sources are in locations where shortages of high quality commercial aggregate exist.

Because of the classical and typical approach to handling of this waste material, very little information exists concerning the existing Southern system bottom ash. The exact character and nature (gradation, chemical composition, presence and amount of pyrite, presence of loosely sintered fly ash particles, etc.) are not known for most of the existing deposits. Certain plant sites are presently using special collection and disposal techniques for

46 Sieve Opening in Millimeters 4.76 9.51 19.0 0.595 1.19 2.38 0.074 0.149 0.297 100

90 • Initial

80 • • Extracted

70 Dry Bottom 60 Ash

4 50

30 Boiler Slag

• 116 18 04 3/8 1/2" 3/4" 1200 1100 050 030 Sieve Site

Figure 2.4. Degradation Displayed by Two Bottom Ash- Bituminous Mixtures after Drop-Hammer

Compaction [ 43 ].

47 the bottom ash in order to more closely control certain characteristics and to make it a more desirable and marketable resource.

Engineering information such as Los Angeles abrasion, specific gravity,

soundness, etc. are also lacking for most bottom ash deposits within the

Southern system ponds. Some inferences can be made about these important characteristics by examining available information found in the technical

literature.

There appears to be some question as to the adequacy of certain laboratory testing methods when used to evaluate bottom ash as an alternate source of aggregate. For example, classical tests such as Los Angeles abrasion and

soundness, even though routinely used to determine quality of conventional aggregate, can often give misleading information as to the toughness and dura-

bility of bottom ash. However, until new evaluation techniques have been de-

veloped and validated to the point that they can be used with confidence, it

appears that conventional test methods must be used.

In summary, it appears that the extent of technical information avail-

able for the bottom ash (new and existing) in the Southern system is sparse.

Additional information is needed in order that guidelines and/or specifica-

tions can be developed to promote optimum utilization of this resource.

48 CHAPTER 3

USE OF BOTTOM ASH AS PAVING MATERIAL

3.1 GENERAL

The use of bottom ash as a paving material has a relatively short history.

The literature suggests that the pioneering work necessary to gain acceptance of bottom ash as a paving material was initiated by Seals, Moulton and others at West Virginia University in the early 1970's. The National Ash Association has, over the years, provided major support and direction in ash utilization.

A major forum for published work on ash utilization has been the Inter- national Ash Utilization Symposia held in 1957, 1970, 1973, 1976, 1979, and

1982 [49,50,51,52,53,54]. The major emphasis in early symposia was concerned with fly ash technology and utilization.

The tremendous highway construction program which has occurred over the

last quarter century has created shortages of natural aggregates in many areas. These recognized shortages of natural aggregates, along with increasing

stockpiles of power plant ash and the popularization of recycling, has provided a major impetus to the use of power plant ash in highway construction.

Although fly ash has found numerous uses both within and outside the highway construction industry, bottom ash is still struggling to gain widespread acceptance as a viable source of paving material. Bottom ash has been used in pavements in the following ways:

1. Unbound aggregate base and subbase material

2. Cement or lime treated subbase and base material

3. Asphalt treated subbase, base, and surface course material

4. Drainage layer

5. Skid resistant material (primarily boiler bottom slag)

49 The amount of bottom ash currently being used in the U.S. for other than fill material is still only about one-third of the quantity being produced

[45]. Interestingly, in England, well over two-thirds of the ash produced has been used [30].

As the electric utility industry increases its coal consumption through new plant construction, and conversion of gas and oil-fired units to coal, more bottom ash will become available. However, whether more ash is used as a paving material depends on a number of complex factors including demand for paving material, type of paving material required, and acceptability of bottom ash as an alternate source of paving material.

3.2 BASIC REQUIREMENTS OF PAVING MATERIALS

Marek, et al. [55], in a research report discussing promising replacements for conventional highway aggregates, address the general requirements of paving materials and their components. Aggregate and binder(s) (where used) for a given service environment control the ability of the pavement to perform its intended function. The characteristics of a pavement required to provide acceptable performance for a reasonable period of time are as follows [55]:

1. Adequate internal strength and stability to distribute surface pres-

sures to the subgrade and to prevent extensive surface deflection.

2. Resistance to deteriorating effects of weather and chemical actions.

3. Resistance to deteriorating effects produced by traffic.

4. Resistance to the effects of internal forces, such as expansion,

contraction, and warping.

5 Limitations to temporary or reversible internal changes in load-

carrying capabilities introduced by environmental elements.

6 Aggregate and binder compatibility.

50 7. Retention of a pavement surface that will assume acceptable standards

of performance. For the surface to have this characteristic, consid-

eration must be given to the following properties:

(a) Skid resistance (b) Surface roughness (c) Glare and light reflection (d) Loose material (e) Tire wear (f) Rolling resistance (g) Noise level (h) Electrostatic properties (i) Appearance

Marek, et al. [55] further indicate that even though aggregates which comprise as much as 90% of the volume of a pavement structure may have desirable properties that allow the pavement system to perform satisfactorily, they must also possess certain characteristics that are dictated by construction procedures. The aggregate, for example, must possess those properties that will allow manipulation and handling during shipment and storage, mixing (with binder or other aggregate), placement and compaction.

Table 3.1 was developed by Marek, et al. [55] to depict the various properties of an aggregate that influence a specific function of the pavement or that are needed to satisfy construction requirements. Note that the relative importance is given for specific properties by various types of pavement material. Unfortunately, the use of aggregate as a stabilized base has not been addressed; however, aggregate requirements for base course application are similar regardless of the type of base material.

In a subsequent study entitled, "Waste Materials as Potential Replacements for Highway Aggregates" [28], bottom ash was placed in Class I (out of four classes) as to its potential. This class is defined as "all possess desirable

properties of aggregates..." Furthermore, it is stated [28] that "bottom ash

has been used with good results in base (course) compositions..."

51 TABLE 3.1 PROPERTIES OF AGGREGATE THAT INFLUENCE SPECIFIC FUNCTIONS (Ref. 55)

RELATIVE IMPORTANCE OF PROPERTY' tN SPECIFIC MATERIAL AGGREGATE FUNCTION PROPERTY PCC BIT. CONC. BASE

I. Adequate internal strength I. Mass stability NA I I and stability to distribute 2. Particle strength I I I surface pressures to the 3. Particle stiffness I I I sttbgrade and to prevent 4. Particle surface texture I I I extensive surface 5. Particle shape I I I deflections 6. Grading I I I 7. Maximum particle size 1 I I 2. Resistance to deteriorating 1. Resistance to attack by effects of weather and chemicals. such as salts I U NA chemical actions 2. Solubility I U I 3. Slaking t I I 4. Resistance to wetting- drying 1 U I S. Resistance to freezing- thawing I U I 6. Pore structure I I I 3. Resistance to deteriorating I. Resistance to degradation 1 effects produced by traffic 4. Resistance to effects of 1. Volume change, thermal internal forces, such as 2. Volume change, wetting expansion, contraction, and drying I N N warping 3. Pore structure I N N 4. Thermal conductivity I N U 5. Limitations to temporary I. Resistance to temporary or reversible internal strength change changes in load-carrying capabilities introduced by environmental elements 6. Aggregate and binder I. Chemical compounds compatibility reactivity 2. Organic material reactivity I N N 3. Coatings I I N 4. Volume stability, thermal I N N 5. Ease exchange I I I 6. Surface charges N I N 7. Pore structure U N N 7. Retention of a pavement surface that will assure acceptable standards of performance. To have this characteristic, con- sit,eration must be given to the following surface "properties: (a) Skid resistance I. Particle shape I I NA 2. Particle surface texture I t NA 3. Maximum particle size N I NA 4. Particle strength I I NA 5. Wear resistance I I NA 6. Particle shape of abraded fragments I I NA 7. Pore structure I I NA (b) Surface roughness 1. Maximum particle size I I NA 2. Grading 1 I NA (c) Glare and light 1. Reflection I I NA reflection 2. Glare I I NA

(d) Loose material 1. Resistance to degradation I' 1 NA 2. Specific gravity N N NA

(e) Tire wear 1. Particle shape I I NA 2. Particle surface texture I I NA 3. Maximum particle size I I NA

(1) Rolling resistance I. Maximum particle size U I NA 2. Particle shape I I NA

(g) Noise level 1. Maximum particle size U I NA (h) Electrostatic I. Electrical conductivity U I NA properties (i) Appearance I. Particle color 2. Oxidation and hydration reactivityty (stains and I N NA 8. Retention of properties 1. Maximum particle size I I I during the construction 2. Resistance to degradation I 1 I process that support all 3. Integrity during heating other functions of the system

• I = Important; N = Not important; V = ImporlarKe unkno..n; NA = Not applic2hle. 3.3 SELECTED EXAMPLES OF FIELD APPLICATION

Numerous references which discuss field applications of bottom ash have

been identified. Additionally, conversations with individuals who have exper-

ience in the area of bottom ash use have provided valuable information. The

primary use of bottom ash has been in base course applications although some

surfacing materials have been composed partially of bottom ash. Applications discussed in this section will be divided into a) those where bottom ash is

used in an unbound state, b) those in which bottom ash has been stabilized with cement or lime fly ash binders, and c) those where the bottom ash is

treated with asphalt.

3.3.1 Bottom Ash Use as Unstabilized Aggregate

A number of cases have been reported in which bottom ash has been used as

an untreated or unbound aggregate [1,4,14,19,48]. Most of the early examples

used boiler bottom slag whereas, more recently, bottom ash has become in-

creasingly popular.

One of the first reported attempts to use bottom ash as a base was in

1971 in a West Virginia access road [4]. Boiler slag meeting West Virginia

specifications was obtained for the ash hopper. The material was then spread

and compacted slightly wetter than the optimum moisture content, using a

10-ton steel wheel roller. Although compaction progressed satisfactorily, the

mix lost stability when it dried. Also, it was suspected that substantial

degradation occurred during compaction.

Base courses for lightly traveled access roads were constructed as a part

of relocation of West Virginia Route 2 [4]. Again boiler bottom slag was

placed and compacted with a steel wheel roller and a 30-ton pneumatic roller.

This material also became unstable upon drying. In another application on

53 this road, boiler bottom slag was blended with blast furnace slag (15 to 40% boiler slag). This material remained stable upon drying [4].

Culley and Smail [14] suggest that the instability problem upon drying could be eliminated by immediate placement of a surface course. In an effort to solve the problem of loss-of-stability upon drying, a mixture of 70% bottom ash and 30% fly ash was tried [4]. Stability problems during field construction indicated a need to change to a 60-40 combination. A vibratory steel wheel roller (with rubber drivewheels) was found best for compaction although as many as 20 passes were required to obtain a stable layer. Some loss in density was observed during a two-month exposure period [36].

Seals, et al. [1] report the construction of a 9-inch thick base course on West Virginia Route 2 composed of a 50-50 blend of bottom ash and boiler slag. This base layer was underlain by a 6-inch cement treated 80-20 (bottom ash-boiler slag) ash mixture, and was topped with 31/2 inches of hot mix asphalt containing only bottom ash and a small amount of boiler slag as aggregate. On

1-79 in West Virginia, Seals, et al. [1] also report the use of 178,000 tons of bottom ash as a subbase. No performance data are reported.

Culley and Smail [14] report the use of "lagoon ash" as a subbase course.

The lagoon ash is a mixture of bottom ash and fly ash. Some screening was required in order to satisfy gradation requirements of the Saskatchewan Highway

Department. The gradation required 100% passing the 3/4 inch screen and 8-13% passing the No. 200 sieve.

A base course 18 to 21 inches thick was used and was topped with 3 inches of hot mix asphalt. After 12 months of service, excellent performance was being exhibited by the pavement [14].

Jones [19] reports the use of bottom ash from Georgia Power's Plant Bowen

for aggregate base in subdivisions at Cartersville, GA. Four inches of bottom

54 ash was compacted to 100% of standard compaction (ASTM D-698) and then topped with 12 inches of hot plant mix asphalt. Although the California Bearing

Ratio (CBR) for the bottom ash was only 25, not a single failure has been reported after three years [19].

In the summer of 1982, the U.S. Forest Service placed a mixture of bottom ash and in situ soil as a wearing surface on a timber sale road in the Oconee

National Forest. No performance data are currently available.

Based on results of laboratory, CBR and resiliency tests Webb [48] has recommended that bottom ash not be used as a subgrade stabilizer in clayey soils. Blends of about 80% clay and 20% bottom ash were used for evaluation.

Furthermore, Webb [48] recommended that bottom ash not be used as a base material; however, he did indicate that use of this material as a subbase could offer potential benefits in high frost areas of north Georgia.

3.3.2 Cement or Lime Stabilized Bottom Ash

In order to overcome some of the problems with stability, gradation control, and construction, bottom ash has been treated with cement or lime to provide a relatively strong, rigid paving material of base or subbase quality.

Based on the information available, it appears that a majority of the bottom ash material being used as a paving material is stabilized with cement. Num- erous examples are found, however, of the use of lime and fly ash to stabilize the bottom ash.

Cement Stabilization

The first known large-scale application of a portland cement stabilized bottom ash base course in the United States was in the 1971-1972 relocation and reconstruction of West Virginia Route 2 south of Wheeling [4,36]. Bottom ash from two sources was blended (because of variations in gradation) and the

55 resulting mix was treated with 5% cement (dry wt. basis). This mix was placed and compacted (with a 30-ton pneumatic roller) to a thickness of 6 inches.

Field densities equalled or exceeded 97% of standard laboratory density. No information, however, was found as to the resulting strength.

The potential use of cement stabilized ash base courses was further studied at West Virginia University in 1972 [4,36]. Mixture design studies were conducted with five different samples of bottom ash from the same power plant; two types of fly ash (silo vs stockpile) were also used. The grain size distribution of these materials is depicted in Figure 3.1. Since earlier work had indicated that high initial stability could be obtained with a 70-30 blend of bottom ash-fly ash, especially when compacted drier then optimum, this blend was used throughout. For comparison, two cement-treated limestone mixtures were also examined. No mention is made of the level of cement treatment; however, it might be assumed that the previously mentioned 5% (by dry wt.) was used.

The results of this study are summarized in Table 3.2. The cement stabilized limestone mixes have a slightly higher strength; however, cement content was not a study variable. Therefore, it is possible that the finer grain size of the ash mixes and the lower unit weight may necessitate a slightly higher cement content (weight basis) in order to attain similar strength.

Clayton [25] reports the use of cement treated boiler slag in southern

West Virginia. In 1975, 200,000 tons of base mix were placed using a treatment level of 11% by weight (5-6% by volume). The estimated in-place cost of the

6-inch thick base was $9.37/ton. When a prime coat and 11/4 inches of surface mix were placed, the total cost per mile was $24,000-25,000.

At a 6% treatment level, compressive strength values less than 300 psi (7 days) led Culley and Smail [14] to conclude that "improvements to be gained from adding (cement)...would not justify the cost."

SIEVE SIZE

3 1v2.. 3/4.. ye . 4 10 20 40 60 100 200 100 ,J

90 *:: -.1mummomr-In Bosom Ash A — 80 1111111111111111111111111111M1 — 0 C A T D GH I 70 NIMIIERM1111111111111 E E 60 111111111111MILIPIME11 Fly Ash H — • BY W S —0

ER 50 011111111111111611011111111111111, FIN

T 40 111111111111111111WEIMENINIMMIN EN

RC 30 11111111111111111MMIERIMM 1EN PE 20 0111111111111111MOMENNENEMEMI

10 11n ^^IIIIIII morampu mum 0 100 10 al 0.01 0.001

GRAIN SIZE IN MILIMETERS

Figure 3.1. Grain Size Distribution of Five Bottom Ash and Two Flyash Materials Used in Special Cement Treatment Study (Ref. 4).

57 TABLE 3.2

SUMMARY OF RESULTS FROM COMPRESSIVE STRENGTH TESTS ON CEMENT TREATED BASE COURSE MATERIALS WITH DRY BOTTOM ASH, FLYASH, OR LIMESTONE AGGREGATES

(REF. 4)

Unconfined Compression Strength (psi) a

Material 8 Days 30 Days 60 Days

Bottom ash A and fly ash H 406 665 726 Bottom ash B and fly ash H 224 505 644 Bottom ash C and fly ash H 478 635 479 b b b Bottom ash D and fly ash H 23 112 163 Bottom ash E and fly ash H 487 512 653

Average 399 579 651

Bottom ash A and fly ash S 520 772 912 Bottom ash B and fly ash S 454 805 681 Bottom ash C and fly ash S - Bottom ash D and fly ash S 313 449 759 Bottom ash E and fly ash S 376 426 560

Average 416 613 728

Limestone PH 525 569 638 Limestone MA 616 961 906

Average 571 765 773

a Average of 3 tests.

b Excluded from average.

NOTE: Believed to be 5% cement treatment level.

58 Probably the most extensive experiences with cement stabilized bottom ash are reported by Kinder [20]. He indicates that 98% of all bottom ash marketed by American Electric Power for use in pavements goes down as cement treated bottom ash [44]. Some of his experiences are as follows:

1. 1974 - a one-mile cement treated (10% by wet wt. of total

mix) ash road was constructed in December;

2. 1975 - 1978 300 miles of secondary roads with 6-inch base plus 1

inch asphalt surface; traffic has varied from 50-75

ADT to 150-1500 ADT, with some heavy truck traffic

included.

3. 1978 - All major access roads at American Electric Power's

Plant Amos were constructed in 1978 using a 6-inch

thick cement treated bottom ash or fly ash topped

with 11/4 inch of hot mix asphalt [44]. The cement

content was about 11% for the bottom ash and 17% for

the cement treated fly ash; resulting 28 day compres-

sive strengths were 1500 psi and 800 psi, respectively.

4. 1982 - Kinder [44] states that no problems with shrinkage

cracks reflecting through to the asphalt surface have

been found. Examination of the Plant Amos roads did

not reveal any types of surface distress even though

many heavy trucks routinely use the road.

Head and Seals [12] report the successful use of both cement treated bottom ash and fly ash as base material for a haul road and parking lot facilities. The haul road consisted of a fly ash fill subgrade, a 51/2-inch thick cement stabilized fly ash base and a 1%-inch thick emulsion-bottom ash surface.

Using a minimum strength criterion of 400 psi @ 7 days, the fly ash required

59 14% cement (dry wt. basis). A mixed-in-place scheme was used for the cement treated fly ash. Fly ash was conditioned with water and then placed. Bulk cement was spread on the surface. Mixing was accomplished by dragging the bucket teeth of a front-end loader through the mix; a tractor-drawn roto-tiller proved ineffective for mixing. Eight months after construction, no distress was noted [12] even though heavy ash disposal trucks used the road extensively.

For the parking lot, a number of different 60 ft. by 70 ft. test sections were used. All sections had a 2-inch asphalt surface and three of the test sections had 6-inch thick base courses composed of:

cement stabilized fly ash (16% cement on dry wt. basis)

cement stabilized bottom ash/fly ash mix (80-20 blend with 12% cement

by dry wt.)

cement stabilized bottom ash (12% cement by dry wt.)

Seven day unconfined compressive strengths were 452 psi, 394 psi and 301 psi respectively.

A continuous-feed pug mill was used to blend the various ash/stabilizing agent mixtures. It was found that the pug mill did not adequately mix the cement-fly ash material. The damp fly ash was thought to be the cause of a

"balling" or clumping of fly ash. A better procedure was suggested which consisted of dry-mixing the fly ash with cement followed by introduction of water. About 6 months after construction (Summer, 1978 to December, 1978) core samples from the bottom ash and bottom ash/fly ash sections gave compressive strength ranging 1100-1650 psi; cores adequate for testing could not be recovered from the cement/fly ash test section (possibly due to low strength).

Webb [48] of the Georgia DOT has extensively evaluated the quality of cement treated bottom ash mixes from a number of Georgia Power's plants.

These results will be discussed in Section 3.4 of this chapter.

60 Lime Stabilization

Lime treatment of fly ash bottom ash has been a somewhat popular method of creating a high quality base course paving material. Fly ash is considered to be a pozzolanic material and as such provides the silica and alumina to the pozzolanic reaction that takes place when lime is added (lime provides the calcium and/or magnesium). The resulting cementing agent is similar to that created when portland cement hydrates. Thus, in order for significant cementing action to take place, reactive fly ash and proper quantities of lime and water must be present. The fly ash portion is that part which is finely divided and passes a No. 200 sieve.

Culley and Smail [14] report that the North Dakota Department of Highways constructed two projects using a combination of 2% lime, 12-18% fly ash, and bottom ash as a base course, with an asphalt surface. A large amount of cracking in the asphalt surface, apparently from shrinkage of the base, was reported. For the "lagoon ash" that Culley and Smail evaluated, a 3% quicklime treatment produced 7-day unconfined compressive strength of about 80 psi; hence, they did not feel that lime treatment should be considered for providing a stabilized base course.

Salow [15] reports the construction of a pavement with a lime-fly ash- boiler slag base course. Mix proportions of 4-29-67 were used. No mention was made of the resulting quality of this mix other than to say that "this road turned out better than our expectations."

Ref. 41, p. 80, presents data which shows for 11 pulverized fuel ashes from England, that 10% lime treatment effects 28-day strengths ranging from as

low as 50 psi to almost 2500 psi.

Rachford [57] has recently reported on the late fall, 1981 construction of almost five miles of relocation road at the Rocky Mountain Project near

61 Rome, Georgia which consisted of a 12-inch thick lime-treated pond ash base course topped with a 1-inch thick asphalt surface. A by-product lime (about

2/3 available lime) obtained from Mineral By-Products, Inc., Atlanta, GA, was combined with pond ash from Plant Hammond. On a dry weight basis, 8% lime was added at the pug mill. Pond ash was combined from two stockpiles in order to obtain a gradation similar to the Georgia D.O.T. requirement for a graded aggregate base. Typical gradation for these mixes is shown in Figure 2.2.

The mix design called for a compressive strength of 500 psi @ 28 days.

Two 6-inch lifts were compacted with a vibratory roller to approximately

100% of standard laboratory density. An automatic finishing machine cut the compacted base to finished grade. Bituminous prime was then applied to seal in the moisture for curing purposes. Although compressive strength varied considerably during construction, test results averaged more than 500 psi at

28 days and over 1000 psi at 90 days. Jones [19] reports that cores taken from this road 6 weeks after construction averaged compressive strengths greater than 700 psi.

The U.S. Forest Service has recently constructed a timber sale road in the Oconee National Forest near Milledgeville, GA. This road has a short section with a structural layer composed of a mixture of by-product lime, bottom ash, and in-situ clayey soil. No other information is available at this time.

Barenberg and Thompson [58] have recently reported on the design, construction and performance of a major access roadway at a Central Illinois

Public Service Company electric generating station. The road consists of a

3-inch asphalt surface over a 10-inch thick lime-fly ash-boiler slag base.

The slag used had 91% passing the No. 4 sieve and only 4.5% passing the No. 50 sieve. The optimum flyash content was that which gave maximum compacted

62 density and was determined to be about 27% of this mix. The lime content was set at 3% by dry weight, producing an unconfined compressive strength of approximately 1800 psi after curing for 7 days @ 100°F.

The mixing plant was set up at the slag disposal area. Conditioned fly ash was delivered, as was dry bulk lime. The lime, fly ash and aggregate components were fed from hoppers to a continuous-flow pug mill. Placement was accomplished with a spreader box and the entire 10-inch lift was spread and compacted in a single lift. A vibratory steel wheel roller was used for compaction. In the next step, a bituminous prime coat was placed to accomplish curing and conventional paving equipment was used to apply the 3-inch thick asphalt surface.

For the first few weeks of construction, the lime contents were quite variable. This was attributed to inexperience of the contractor and poor mechanical condition of the plant [58].

Some longitudinal and transverse cracking, and very limited fatigue cracking, has occurred on this heavily traveled roadway after 5 years of service. The performance however has been termed "good" by the authors [58]

Majidzadeh, et al. [2] report that the State of Ohio has constructed numerous fly ash-lime stabilized bases using bottom ash material (type unknown).

The lime-fly ash base mixtures typically consist of 85% bottom ash, 10% fly ash, and 5% lime. The material was graded to meet the State of Ohio's specifications. No other details were given [2].

Webb [48] of the Georgia D.O.T. has extensively evaluated the quality of lime treated bottom ash mixes from a number of Georgia Power's plants. These results will be discussed in Section 3.4 of this chapter.

63 3.3.3 Asphalt Mixtures Containing Bottom Ash

The use of bottom ash in asphalt mixes for surface or base has apparently not been as extensive as has been cement and lime treated bottom ash base applications. Nevertheless, as a result of an FHWA study, fairly extensive literature has been found which deals with various aspects of asphalt-bottom ash mixes.

Majidzadeh, et al. [2] in their literature review indicate that bottom ash-modified asphaltic mixtures have been used in Ohio, West Virginia, New

Jersey, Illinois, Indiana, Florida, Iowa and Texas. They also indicate that many miles of secondary roads, city streets and parking lots have been paved or resurfaced with asphalt mixtures containing bottom ash materials.

Most of the literature and applications reported in the early to mid

1970's dealt with wet bottom boiler slag applications; however, more recent information addresses dry bottom ash applications. Since a fairly lengthy history is available for boiler slag-asphalt mixes, both boiler slag- and dry bottom ash-asphalt mixes will be briefly discussed in the following sections.

Asphalt Mixtures Containing Wet Bottom Boiler Slags

Seals, et al. [1] in 1972 stated that "boiler slag has received the widest acceptance and, therefore, the widest use." At that time (1972) the

State of Indiana allowed for its use in hot asphaltic surface course paving mixtures. The specifications allowed for the following mixture by weight:

boiler slag 55-70% sand 25-35% mineral filler 3-6% bitumen 5-8%

Seals, et al. [1] also reported that the City of Cincinnati allowed the use of a mixture composed of boiler slag 60% river sand 24.5%

64 fly ash 8% asphalt cement 7.5% (75-85 pen grade)

Apparently, these mixes were believed to possess excellent anti-skid properties [1]. Others [4,36,41], though, have refuted the desirability of boiler slag as a premium aggregate for skid resistance because of its lack of aggregate micro-texture, which is necessary for skid resistance and the ability to retain its asphalt coating.

For use in stabilized base applications, Moulton, et al. [4] state that boiler slag "because of its glass-like surface texture and uniformity... possesses little internal stability and must generally be blended with other aggregates in order to produce acceptable bituminous mixtures." These authors

[4] continue and briefly describe the use of these mixes in northern West

Virginia for resurfacing. Overlays with a thickness ranging from 1/2 to 2

inches have been placed with conventional asphalt paving procedures. They

state that "performance under heavy truck traffic has been good with little or no tendency to rut or shove..." (after 5 years of service). Anderson, et al.

[33] noted that in a similar application, a problem in aggregate retention was encountered in the wheel tracks.

Anderson [32] briefly discussed the merits of boiler slag for asphalt mixtures. He states:

"It (boiler slag) is hard, abrasion resistant, not absorptive and

shows good resistance to stripping (water associated loss of bond

between asphalt and aggregate). The best results have been in

blends with natural aggregates with the percentage of slag limited

to 40-50% of the total aggregate. This (limitation) is necessary

to control mixture gradation (without crushing the slag) and to

control stabilities. Boiler slag mixtures that do not contain

65 crushed natural aggregate lack stability as verified by field

experience and the data presented by Shuler and Wood [40,59],

Figure 3.2.

Anderson, et al. [33] state that boiler slag can be used in conventional applications without any special consideration if the percentage of boiler slag is limited to less than 50% of the total aggregate.

Asphalt Mixtures Containing Dry Bottom Ash

Concerning the use of dry bottom ash in asphalt mixes, Moulton, et al.

[4] in 1973 stated that they

"know of no reported use of dry bottom ash in surface or wearing courses. The inherent stability of this material, along with an acceptable soundness and abrasion loss, suggests that this material might be used as an acceptable surface mix for light or medium traffic. There is a tendency for some of the more loosely agglom- erated bottom ash particles to degrade under the action of heavy traffic."

Anderson, et al. [33] in 1976 presented a paper dealing with power plant aggregate in bituminous construction. In discussion of mixture properties, these authors indicated the following:

1. Kneading compaction produces substantially higher density (in lab)

than found with Marshall specimens using 50 blows per side. (Usmen

and Anderson [22] state that drop hammer compaction does not adequately

compact bottom ash mixtures).

2. Low Marshall flow values (ASTM 0-1559) are typical of these mixtures;

this indicates a tendency toward brittleness. Thus, these mixtures

may crack more readily and extensively than bituminous mixtures made

with conventional aggregates.

3. High compacted air void contents, even for well graded mixtures, are

typical due to the high internal friction and rough surface texture.

66 9.0

8 .0

5.0

4.0

0 I 0 25 35 50 % ASH

Figure 3.2. Contours of Equal Marshall Stability (lbs.) for Various Sand-Bottom Ash-Asphalt Mixtures (From Ref. 40).

67 4. The presence of loosely sintered fly ash or "popcorn" particles which

causes problems with asphalt coating and later particle disintegration

may make the use of these mixtures in surface courses undesirable.

5. Bottom ash containing iron pyrite may be a major problem. The pyrite

is subject to degradation in the pavement and should be eliminated

from ash that is to be used in bituminous construction.

6. Dry bottom ash is best used in base mixtures or for shoulder construc-

tion. For surface use, the bottom ash should be blended with other

aggregates.

In another paper, Usmen and Anderson [22] indicate that some bottom ashes contain a small amount of sulfate and other soluble salts that occur as a deposit on the surface of the ash particle, although the exact source of these salts is not known. They state however that these salts cause no harm in the pavement except for a temporary white stain on freshly laid pavement. They continue, however, and reveal that the presence of iron pyrite particles will weather in the pavement, producing popouts at the surface and weak pockets within the mix.

These surface popouts have been observed in Georgia for two asphalt mixtures containing a blend of dry bottom ash and conventional crushed aggregate. The popouts were characterized by:

I. a small hole partially filled with gray powder

2. a brown and white stain surrounding the hole

It is believed that the observed characteristics are due to a weathering of the FeS 2 to plus a sulfate compound. The brown stain is "rust" and the Fe203 white is most likely a soluble sulfate; the gray powder is most likely either fly ash or Fe0 powder.

68 Usmen and Anderson [22] looked at a number of considerations with regard to the use of bottom ash in asphalt mixes; some pertinent findings included the following:

1. Bottom ash-asphalt mixtures, when evaluated in the immersion-Marshall

test, yield acceptable stability retention values (acceptable range

being 75% or above).

2. Bottom ash, because of its surface texture, tends to have a higher

asphalt demand than natural aggregate. Kneading compaction (in lab)

more closely approximates field compaction (e.g., it gives higher

density) and as such gives a more realistic estimate of asphalt

demand and air void content.

3. Bottom ash is usually less dense (lower specific gravity) than con-

ventional aggregate and therefore asphalt content should be based on

volume rather than weight. For example, a bottom ash mix at 110

lbs/ft 3 with an asphalt content of 9% is comparable to a 7% asphalt

content for a conventional 140 lbs/ft 3 mixture.

In an effort to reduce both the asphalt demand and the air voids in compacted mixtures, several investigators have evaluated blends of dry bottom ash and natural aggregates [17,40,59]. Both asphalt demand and air void content can be reduced by increasing the amount of conventional aggregate in the blend.

Kinder [44] indicated that in West Virginia the only bottom ash being used in asphalt mixes is as a sand substitute. He also indicated, based on his experiences, that unless the bottom ash is blended with conventional aggregate, the bottom ash tends to "ball up" during mixing with the asphalt.

This may be due to the low density or specific gravity of the bottom ash in

West Virginia (specific gravity = 2.15).

69 Majidzadeh, et al. [17,65], after completing a major research project for the Federal Highway Administration concerning the use of power plant bottom ash in black base and bituminous surfacing, concluded the following:

I. Generally, bottom ash requires more asphalt than a natural aggregate

with the same gradation characteristics; more porous bottom ash

particles will require more asphalt.

2. Dry bottom ash-asphalt mixtures generally exhibit higher air voids

content than conventional aggregate mixes. This is largely due to

the high friction angles and rough surface texture of the ash par-

ticles.

3. Resilient moduli values were found to be 1/3 to 1/2 of those of

standard mixes.

4. Although fatigue response was evaluated, no comparison was made to

conventional mixes. It was found that fatigue life increased with

asphalt content and higher ash contents (in aggregate-ash blends).

5. A relatively high rutting susceptibility was found for these mixes.

6. The experimental results indicated that moisture damage is not critical

in these mixes and that in fact, immersion appeared to cause an

increase in mix stability.

7. Dry bottom ashes can, in most instances, be used in bituminous mix-

tures for both surface and base course applications, as well as in

other non-wearing applications.

8. These materials can generally meet standard aggregate specification

limits although some specifications and standard testing methods may

not be appropriate for these materials.

9. Bottom ash can be used to design a durable, stable mixture that

should perform satisfactorily.

70 Majidzadeh, et al. [17,65] continued with conclusions concerning both dry bottom ash and boiler slag:

1. Bottom ash aggregates can be selected to meet soundness, hardness and

other quality specifications as required by state transportation

agencies;

2. These materials, where properly selected, can resist degradation

under compaction and retain their size distribution and particle

angularity characteristics;

3. Bottom ash can be used as partial or full substitute for conventional

aggregate materials in bituminous mixtures. These mixtures can be

designed to meet any or all job requirements for durability and

stability, modulus of resilience, fracture toughness, and fatigue, as

required by user guidelines.

These authors also recommended guidelines for (a) material selection,

(b) testing and evaluation, and (c) mixture design and evaluation. These

guidelines will not be included in this part of the discussion, but have been

attached as Appendix A.

In addition to the use of dry bottom ash in hot mix applications, exten-

sive use has been made in emulsion-bottom ash mixtures often termed "ASHPHALT."

These mixtures, prepared by cold mix pugging procedures, have been used exten-

sively in low volume roads [2,22,32,33]. In this application, MS-2 or CMS-2

emulsified asphalt is blended (6 to 8% residual asphalt content). Anderson

[32] indicates that cold mixes containing bottom ash are more forgiving of

gradation variations than those containing conventional aggregates. Anderson,

et al. [33] reported that the cost of these mixtures was about one-half to

two-thirds the cost of a conventional hot mixture.

71 Field lay-down experience with this material was reported as excellent

[33]. Although the material was a bit fluffy in the spreader, little or no difficulty was encountered whether the material was placed with a paver,

spreader box or merely end dumped and leveled with a grader. Lifts 6 to 8

inches thick were placed and compacted with 4 to 5 passes of a pneumatic-tired

roller.

3.4 OTHER PERTINENT STUDIES

The main source of information relative to the use of bottom ash for

highway purposes has been Seals, Moulton, and Anderson [1,3,4,6,22,32,33,43].

A recent study by Majidzadeh [2,16, 17,65] sponsored by the Federal Highway

Administration has added substantially to the literature in the area of asphalt

treated power plant ash for highway use. Various aspects of these studies

have been discussed previously in this report. Shuler [40] conducted an

excellent study in Indiana concerning the effects of bottom ash upon bituminous

sand mixtures.

Numerous other studies probably have been conducted but the results have

not been widely publicized in the technical literature.

One source of information concerning laboratory studies of bottom ash has

been made available from the Georgia Department of Transportation [48]. The

Georgia D.O.T. laboratory at Forest Park has been involved in examination of

various bottom ash mixes since 1979. Evaluations have been made as to the

potential for (a) graded aggregate base and subgrade stabilization and

(b) cement or lime stabilized base. In addition, a limited amount of labora-

tory work has been done in regard to the use of bottom ash in asphalt mixes.

It is believed that a presentation and brief discussion of this work is germane

to this technical data base report.

72 Discussion of the laboratory work regarding graded aggregate base and subgrade stabilization has been presented in Section 3.3.1. Georgia D.O.T.

[48] has basically concluded that bottom ash should not be used as either a graded aggregate base or to provide subgrade stabilization.

The results of laboratory studies concerning treatment with cement or lime are summarized in Table 3.3 . Examination of these results indicates a somewhat erratic and variable compressive strength response.

Cement Treatment

Treatment of the fine ash from Plant McDonough (1979) with 3.4 to 6.7% cement (by dry weight) produced minimal strength increases at 7 and 28 days.

Treatment of fine bottom ash from Plant Bowen (April 23, 1980) resulted in quite substantial strength increases, Table 3.3. At 6% cement (dry wt. basis) over 600 psi compressive strength was noted at 7 days. Another finely graded bottom ash sample from Plant Bowen (June 22, 1980) gave similar response to cement treatment. For the laboratory study reported on June 22, 1980, compressive strength at any treatment level decreased as the bottom ash sample became more coarsely graded. This is most likely due to an improper gradation with a deficiency of fines.

It is interesting to note the unusual values for Y and W (GHD d max opt #24) for the 1979 study. The low value of Y d max = 73 pcf and high value of W = 28% are substantially different than any other values shown in Table opt 3.3, although such unusual values have been reported [1]. Higher Yd -values and lower W values normally occur for similar Georgia materials. As an opt example, for the June 22, 1980 tests with cement, Z'd max = 121.8 pcf and W opt = 7.5%.

If, in fact, 73 pcf is correct, 3.4 to 6.7% by wt. cement treatment is extremely low on a volume basis. For a mix unit weight of 73 pcf, 5% cement

73 LABORATORY TEST DATA FROM STUDIES OF TREATED BOTTOM ASH AS A BASE MATERIAL-GEORGIA DEPARTMENT OF TRANSPORTATION (Ref. 48)

Moisture-Density Compressive Strength, Appr,y_i-,ate Additive Bottom Ash Crain Size. 1 Passing GBD 024 psi Dale Type Source Coutent-I-Cuellig Cc.nditijiT;-] 1" 3/4" 1/2" 3/8" 04 010 040 060 #200 Y dnox'P cf 1 wopt, 2 741077F Md:;;A 3.4 75 69 1979 Cement McDonough 100 94 84 50 27 73.0 28.0 5.0 101 135 6.7 139 7 darn 0 128°F 5.0 358 Ildrated McDonough 100 94 84 50 27 70.9 29.5 10.0 672 Lime 15.0 • 116 7d 2 77'.F 2Ed i 7:T -114 s8.5 Ciplus 453 403 Cement April 23, Bowen 99 97 91 48 32 18 14 6 (114.8-113.0) (8.1-9.1) 6 10% 624 687 (plus 10% 1950 range range S flyash 749 903 flyash) 7d@ 100°F 141 100'.7 Puzzolime (plus 8% -110 -9.5 4 plus 284 772 flyash) Bowen . 99 97 91 48 32 18 14 6 (107.5-113.0) (9.0-10.0) 6 HZ 525 987 range range 8 flyash 685 1198 7 days -3 77'F Bowen 3 F5 Varioos Coarse 99 97 93 45 28 22 8 106.0 10.9 5 149 blonds June 22, Cement of 67% C 3 106 99 97 93 48 33 28 13 111.0 10.0 1980 con SC 33% F 5 .172 and 50% C 3 169 fine 99 98 94 50 35 31 16 116.2 10.2 50% F 5 201 ash 3 170 Fine 99 98 95 54 41 39 23 121.8 7.5 5 420 14d 0 77 0 1 502 r Oct. 9. 1080 Bowen Evaluation (Coarse) 99 98 95 43 16 11 3 95.8 13.5 6 70 170 Pozzo/lme icy possible (Fine) 99 98 95 50 34 30 15 121.9 9.5 6 400 1100 LIEQ Deki.lb Feathtrce Airport 7 days '7 100 ) F 4 28 Nov. 5, Pozzolime Arkwright 98 95 86 42 31 25 11 122.0 8.2 '6 31 1961 8 26 7 days 3 1000 F 4 38 Pozzolime Wansley 99 98 95 51 26 11 2 113.7 10.7 6 59 8 67 7 days 2 100°F 4 Harney 30 Pozzoilme 100 99 97 68 47 40 18 99.5 13.0 6 35 Branch 8 4 1 7 days 2 100° F 4 24 Harllee Pozzolime 100 100 99 90 71 62 32 88.3 17.5 6 32 Branch 8 38 (Continued)

Moisture-Density Compressive . Strength, Approximate Additive Bottom Ash Crain Size, Z Passing . Dare Type Source CUD 824 psi 1" 3/4" 1/2" 3/8" 84 810 840 860 8200 1 ma pcf w % Content,1 Curing Conditions d x' opt' @ 100 ° F Sept. 1982 Pozzolime Marilee Branch 7d 14d 28d Pond C 99 98 97 92 78 62 43 37 17 99.1 12.8 4 42 204 324 6 60 335 496 8 61 212 472

Pond D 95 94 92 89 77 60 20 15 6 103.2 11.4 4 42 105 300 6 62 140 320 8 59 1G8 166 @ 73° F 7d 14d __.28d Cement Marilee Branch 4 151 176 241 Pond C Sane As Above 102.5 11.9 6 220 218 308 8 251 286 479

4 113 127 170 Pond D Same As Above 104.1 12.0 6 165 199 321 8 162 297 425 by weight occupies 0.039 ft' (bulk unit weight of cement = 94 pcf); if the compacted unit weight were 140 pcf, a 5% treatment level occupies 0.074; thus, almost twice the volume of cement exists even though the treatment level on a weight basis is constant.

Thus, even though some results to date suggest that cement will not adequately "stabilize" some bottom ash mixes, other data (Table 3.3) and results from West Virginia, suggest that cement treated bottom ash can produce a very high quality base material if important mixture variables are recognized and adequately controlled.

Lime Treatment

In the case of cement treatment, it is normally accepted that commercial cement will be of high quality and if used in reasonable quantities and proper mix gradation, good compressive strength can be obtained. However, with lime, adequate cementing develops in the system if a) reactive fly ash is present in a proper quantity and b) a good quality and proper quantity of lime is present to activate and sustain the pozzolanic reaction. Simply providing lime and fly ash or fine ash in the mix may not be sufficient.

For the laboratory testing summarized in Table 3.3, only 1 of the 10 mixes treated with lime used a commercially available hydrated lime; the other mixes were treated with "pozzolime," a by-product lime provided by Mineral-

By-Products, Inc., Atlanta, Georgia. The ability of this lime to initiate and sustain a pozzolanic reaction was not addressed in the reported laboratory study and hence is not known.

In terms of the strength exhibited by mixes containing lime of either source, the results shown in Table 3.3 indicate the varied response of mixes treated with Pozzolime. Some mixes responded quite well (see April 23, 1980 and October 9, 1980) while others (November 5, 1981) exhibited virtually no

76 strength increase. The 1979 study which used commercial hydrated lime in the fine bottom ash mix showed a fairly high strength increase, although an accel- erated cure (7 days @ 128°F) makes direct comparison to other strengths somewhat difficult.

Based on these varied results, and also on the results reported by Baren- berg and Thompson [58], as well as the extensive and positive history of lime-fly ash treated base materials, it appears that lime-treated bottom ash can provide an excellent quality base material; however, certain mixture variables must be controlled, particularly the amount and pozzolanic quality of the fine fraction and the quality of the lime.

3.5 MATERIAL AND CONSTRUCTION SPECIFICATIONS FOR BOTTOM ASH

3.5.1 General Considerations and Discussion

Specifications are commonly used to control or ensure the quality of a given material. For highway materials, specifications may be imposed on the individual materials of a composite as well as the composite or mixture itself.

In addition, controls or specifications may be imposed on the construction process.

Many, if not all, specifications in the highway materials area have been developed based upon many years of laboratory and field experience. Materials used and/or constructed in accordance with these specifications usually exhibit adequate performance.

A dilemma that may be encountered when a "new" material is proposed for use in pavement construction. Performance records are not available. Selec- tion criteria are either difficult to establish or non-existent. Faced with such a situation, existing specifications are applied. This may lead to an unsatisfactory result (performance) even though specifications are satisfied;

77 on the other hand, it is possible that the material will not be used because it is "out-of-spec" even though excellent results might have been achieved.

Widespread acceptance of bottom ash for use in pavement layers is dependent on the availability of pertinent specifications--particularly those of state highway agencies. Commonly, private work utilizes local state specifications. Unfortunately, widespread acceptance of bottom ash does not exist.

In 1976, a survey [45] of state specifications indicated that 30 states have specifications allowing the use of power plant ash, including fly ash; a limited number allow the utilization of boiler slag but only a few allow the use of dry bottom ash [2]. Even West Virginia, one of the largest users of bottom ash, does not have a general specification for dry bottom ash although one is currently under consideration [44].

Moulton, Seals, and Anderson [4] summarized the state of thinking in 1973 by stating:

"The experience that has been accumulated to date on the utilization of bottom ash (boiler slag) and fly ash in highway construction has raised serious doubts as to the applicability of existing materials and construction specifications....There is a very defin- ite need to recognize that bottom ash and fly ash have unique chemical and physical properties and to consider these materials apart from conventional highway construction materials. If ash is to be used effectively in highway construction, new specifications must be developed that take into consideration the unusual properties of ash and the specialized construction techniques required to ensure adequate performance. Assuredly, this will require additional study, both in the laboratory and in the field. However, interim specifications based on performance would open the way to expanded utilization of ash in highway construction and provide a fund of data on which more detailed material and construction specifications could be based."

In 1976, Miller and Collins [28] recommended the following in order to better utilize waste materials as replacements for highway aggregates:

"Existing specification requirements for aggregates should be thoroughly reviewed and analyzed with an eye toward relaxation of certain requirements, particularly in areas where shortages of conventional aggregates are now or will become a problem. Consider- ation should be given to the adoption of performance specifications,

78 even on a trial basis, in order to allow more latitude in the selection of highway materials."

Usmen, et al. [43] have discussed in detail the applicability of conventional test methods and material specifications to coal-associated waste aggregates (including bottom ash). They conclude that because of the unique characteristics of bottom ash, boiler slag, etc., application of conventional test methods and specifications is often inappropriate and that effective use of such materials requires the development of new test methods or modifications to existing methods and specifications. They suggest the following questions must be answered relative to the use of bottom ash:

1. What are the physical and chemical properties of the bottom ash and

what is its variability?

2. How do these properties affect design, construction and performance?

3. How can existing tests and specifications be used to assess proper-

ties and predict performance?

4. What modifications to the methods and criteria are needed?

5. What performance data are available as guidelines to modify or verify

Steps 1 through 4 above?

Based on the foregoing, it is apparent that acceptance and use of a material such as bottom ash requires specifications which can be applied with confidence; however, existing test methods and specifications may have some limitations and liabilities which curtail their applicability to bottom ash.

3.5.2 Existing Specifications and Guidelines

Although no specific survey of state highway agencies was taken as a part of this study, literature and personal contacts served to identify a number of specifications and guidelines.

Majidzadeh, et al. [2] as a part of their study found specifications/

guidelines (1977) available from the following states: Illinois, Kansas,

North Dakota, Ohio, and West Virginia. The particular specification/guidelines

identified by Majidzadeh, et al. [2] have been included in Appendix B. The

general focus of each specification/guideline is as follows (date adopted is

also shown): Illinois - Wet bottom boiler slag for fine aggregate in bitumi- (1971) nous mixes; ok for coarse aggregate use, but not in bituminous mix.

New Jersey - Boiler slag for coarse aggregate; X > 85 pcf, Gs 2.8, absorption 5. 1.2%, and some gradation control Kansas - Special provision for use of boiler slag as coarse (1970) aggregate in bituminous mix; proportions established as: slag - 64%, sand - 32%, mineral filler - 4%

North Dakota - Use of fly ash as mineral filler only, no bottom ash recognized

Ohio - Supplemental specification for use of steam boiler (1969) slag asphalt mix for surface course (40% slag, 60% sand); requirements on gradation, fineness modulus, and soundness

West Virginia - Air cooled blast furnace slag is satisfactory or (1972) "other slags having demonstrated a satisfactory record or which meet applicable physical requirements (presumed to be gradation, abrasion, soundness, etc.) for blast furnace slag, may be used with the approval of the engineer." Boiler slag may not be used as aggregate in portland cement concrete.

In addition to the previous, the following specifications/guidelines have

been found:

1. Kinder [20] - Guidelines for cement-treated bottom ash; these were developed from field and laboratory experience and cover (a) materials, (b) mixing operation, (c) spreading, (d) compaction, (e) curing, and (f) tests.

2. National Ash - Guide for the design and construction of cement Association stabilized fly ash pavements; this publication [31] covers mix design, thickness design, and specification guidelines for materials and construction

80 3. Saskatchewan Highways and Transportation Specification for Subbase Course (with modification for lagoon ash) [14]

- Coverage includes materials and construction

4. Majidzadeh, - Recommended guidelines for material selection, et al. [17] testing and evaluation, and mixture design and evaluation (relative to use of bottom ash in asphaltic mixtures)

All of these guidelines/specifications, except those of Majidzadeh, et al. [17] (see Appendix A) have been included in Appendix B. Of these, probably those from Kinder [20], the National Ash Association [31] and Majidzadeh, et al. [17] are the most comprehensive. The State of West

Virginia [44] is currently considering the adoption of a specification which will cover treated bottom ash.

3.6 DISCUSSION

The use of bottom ash as a paving material has a relatively short history. The most extensive reported use of bottom ash has been as a stabilized base course material, particularly in the West Virginia area. Cement, lime and asphalt have all been used as the stabilizer, with cement the predominant additive. Majidzadeh, et al. [17,65], after completing a major research project concerning the use of power plant bottom ash in black base and bituminous surfacing, concluded that bottom ash can be used as a partial or full substitute for conventional aggregate materials in bituminous mixtures.

Furthermore, they concluded these materials can generally meet standard aggregate specification limits, although some specifications and standard testing methods may not be appropriate. Some limited use of bottom ash as a graded aggregate material has been reported.

The use of bottom ash in pavement applications in the region encompassed by the Southern system has been extremely limited. In visits to state high-

81 way agencies in Alabama, Florida, Georgia, and Mississippi, only Georgia and

Mississippi indicated serious previous consideration for use of bottom ash.

The Georgia DOT has been experimenting with Georgia Power bottom ash for a

number of years; however laboratory results have been erratic. Many of their

studies have used by-product lime, however, which is also a relatively uncon-

ventional waste material often leading to erratic results.

A major problem associated with ponded ash is that of gradation. Depend-

ing on disposal methods and location within a pond (with respect to the sluice

pipe), substantial variations in gradation can be expected with both horizontal

and vertical position. Co-disposal of flyash and bottom ash will result in a

relatively fine gradation, particularly at some distance from the outfall

(i.e., sluice pipe). At the Georgia Power Rocky Mountain Project in north-

west Georgia, gradation control was obtained through the use of visual estima-

tion to combine coarse and fine ash. Substantial variations were encountered,

however as indicated by the range shown in Figure 2.2.

Ideally, for use in stabilized base or subbase course applications, ex-

perience would indicate that a dense gradation is most desirable and mini-

mizes the amount of stabilizing agent required to obtain a given strength

and/or durability. Of course with asphalt mixes, it is imperative to have

good control over gradation in order to maintain stability, void content

and asphalt content requirements.

Barenberg and Thompson [58] report that in the mix design of a lime-

flyash-bottom ash mixture, sufficient flyash was added to produce the maximum

compacted density for the flyash-bottom ash blend. This was an amount just

sufficient to fill void space in the bottom ash with flyash.

Analysis and control of the gradation of aggregate blends can be done

visually or by analytical methods. Studies by Fuller and Thompson [72] have

82 indicated that a maximum density can be obtained for an aggregate when the exponent n = 0.5 in Equation 3.1.

p = 100 (d) (3.1)

where: d = Sieve size in question

p = % finer than the sieve size

D = Maximum size of aggregate

n = Exponent which adjusts the gradation curve in a finer or coarser position

Figure 3.3 depicts the theoretical gradations required for dense mixes with maximum particle sizes of 1 inch, 3/4 inch, and 3/8 inch where n = 0.5.

Many of the mixes shown in Figure 2.2, including those for the Rocky Mountain

Project are, in general, on the "fine" side of a dense mix.

It appears, based on the literature and experience, that bottom ash con-

taining pyrite is an undesirable component in asphalt mixtures used as sur-

facing. It is not known whether bottom ash containing pyrite will cause

problems when used in stabilized or unstabilized based course applications.

Information obtained during this technical data base study did not make

it clear as to whether cement or lime-treated bottom ash mixtures exhibit

tendencies toward shrinkage cracking.

Another interesting feature of bottom ash mixtures is their low compacted

unit weight. Compacted unit weights as low as 70 pcf were reported in the

literature. Since stabilizer contents are commonly based on the dry weight

of bottom ash, treatment levels in the range of 4-6% are substantially less

on a volume basis than a similar treatment level for a typical granular mater-

ial with a compacted unit weight of 130-140 pcf. Usmen and Anderson [22] in

fact, recommend that asphalt contents should be based on volume rather than weight. 83 100

d 0.5 p = 100 (b-) 80 z 60

0 - 200 40 20 10 4 3/8" 3/4'1" SIEVE NUMBER

Figure 3.3. Theoretical Gradations Producing Maximum Density.

84 The significance of this situation is that comparison of stabilizer contents, particularly with conventional aggregate mixes, should be done on a volume basis, rather than a weight basis. The effect of unit weight on stabilizer content should at least be given appropriate consideration.

Acceptance and use of bottom ash requires testing methods and specifications which can be applied with confidence. Evaluation of bottom ash materials using conventional test methods and material specifications has been ques- tioned. Usmen, et al. [43] have concluded that because of the unique characteristics of bottom ash, application of conventional test methods and specifications is often inappropriate, and effective use of such materials requires the development of new test methods, or modifications to existing methods and specifications.

85 CHAPTER 4

ECONOMICS'ASSOCIATED WITH BOTTOM ASH USE

4.1 INTRODUCTION

The rate of future use of power plant ash materials in highway construction depends primarily on two factors: (a) general acceptance of the material as an alternate paving material and (b) attractive economics. Previous discussion has been devoted to properties and characteristics of bottom ash and

various types of paving mixtures containing bottom ash. The purpose of this

chapter is to discuss various aspects of the economics associated with bottom

ash use in pavement layers. A number of references contain information pertin-

ent to the economics of bottom ash utilization [3,8,18,19,20,25,29,31,32,34,

36,37].

4.2 GENERAL CONSIDERATIONS

The economics of bottom ash utilization must be examined from the per-

spective of both the producer (the power company) and the consumer (the ulti-

mate user). Two excellent references concerning bottom ash economics are [3]

and [18].

4.2.1 Producer

Utilities in the Southern electric system operate coal-fired power plants

with a total of 64 generating units currently on-line. These coal-fired power

plants produce in excess of 4 million tons of fly ash and bottom ash per year.

Disposal of this ash material represents a major expense to the electric

utility. On a national scale, estimated disposal costs for the electric

utility industry in 1980 were 5375 million to 5740 million with a per ton

disposal cost of S5 to S10 [61].

86 Disposal costs incurred by electric utilities are often difficult to break down into contributing categories; however, the following list seems to identify major contributors:

1. Ash collection equipment; capital investment, operation and mainte-

nance

2. Ash handling equipment and operations; capital investment, operation,

and maintenance

3. Temporary and permanent storage facilities such as silos, ash ponds,

etc.; capital investment, operation and maintenance

4. Taxes on properties and/or equipment dedicated to ash collection,

handling and storage

5. Time value of the money invested in ash collection, handling and

storage

The availability of a market for these ash materials could dramatically reduce portions of the overall cost associated with the ash materials. Unless a market is available for disposal of these materials, the ash must be disposed of by storing in on-site ponds or hauling to disposal or landfill sites.

On-site disposal ponds require sizeable capital investment. When these ponds become filled, either the ash material must be removed at considerable cost or new ponds must be constructed, also at considerable cost. Ratcliffe [70] has stated that for 1981, the average costs for ash pond excavation and disposal

(1 mile haul) was $3.00 per ton; also, ash pond dredging costs were $1.50 per ton.

Based on the total economics of ash collection, handling, and disposal or storage, marketing of ash materials could be beneficial in several ways, including reduced disposal costs and increased life of disposal areas, as well as income derived from actual sales to the user.

87 The development of a marketable commodity may require additional capital investment by the utility company, although ash brokers often do this now.

For example, dry storage of fly ash requires special facilities; use of bottom ash as a light-weight aggregate for cinder block requires pyrite-free ash; certain uses for bottom ash may require its separation from fly ash during disposal (that is, fly ash and bottom ash must be disposed in separate ponds).

4.2.2 Consumer

The economic benefits and costs of using power plant ash will vary geo- graphically as a result of demand and supply of construction materials. The cost of utilizing a particular material such as bottom ash depends on the cost of producing and/or processing the material and the cost for transportation.

Currently, it is believed that the maximum economic haul for bottom ash is 30 to 50 miles [8,28].

When considering the cost of alternate materials for use in a pavement, however, it is important to consider the quality and structural contribution.

For example, if for a typical base course application, alternate designs required 12 inches of crushed stone or 9 inches of cement treated bottom ash, the cement-treated bottom ash could cost one-third more on a volume basis than the crushed stone and still have the same pavement cost.

For comparison purposes, the following summary presents typical relative strength values (layer coefficients) and crushed stone thickness equivalencies:

Approximate Material Layer Coefficient [60,62] Thickness Equivalency

Crushed Stone 0.14 1:1

Asphaltic Concrete 0.44 3:1 surfacing (upper 4-1/2 inches)

Approximate Material Layer Coefficient [60,62] Thickness Equivalency Base (below 4-1/2 0.30 2:1 inches) Cement Treated 0.22 1.6:1 Aggregate

Soil Cement 0.20 1.4:1

Lime-flyash-aggregate 0.28 2:1

Lime-bottom ash [57,58] 0.28 2:1

Paving materials containing large portions of bottom ash normally have lower compacted unit weights than conventional materials containing crushed stone. On a weight basis even a larger difference in alternate material cost could produce equal total costs.

An additional consideration from the consumer's perspective is related to the possible "premium" that a contractor may charge as a result of a nuisance factor -- using a material with which he is not extremely familiar. The methods and equipment used by a typical highway paving contractor may not easily accommodate a "new" material. Because of the "new" material, the contractor may need different or additional equipment, handling techniques, etc. and his productivity may be adversely affected; the uncertainty or actu- ality of such can only be reflected in higher costs to the consumer.

The economics of bottom ash utilization are ultimately related to the net cost of the paving layer and the future performance of the pavement.

4.3 SPECIFIC EXAMPLES

Because of the complexity caused by many of the economic factors previously discussed, it is often difficult to make direct economic comparisons between conventional paving materials and those containing bottom ash. However, insofar as possible, specific examples found in the literature and in discussions with various individuals will be presented.

89 Anderson, et al. [33] reported the cost of "ASHPHALT" mixtures used on low volume roads in West Virginia to be about one-half to two-thirds the cost of a conventional hot mix.

The Georgia Power Company has recently completed 5 miles of a relocation roadway associated with the Rocky Mountain Project, wherein a by-product lime/bottom ash mixture was bid as an alternate to a crushed stone base.

Specifications called for 8 inches of crushed stone base and 5 inches of asphaltic concrete leveling and wearing course. The alternate specification required 12 inches of lime-bottom ash base and 1-1/2 inches of asphaltic concrete wearing surface. Based on actual bid prices received for the two alternative pavement designs, a substantial direct cost savings was realized by using the ash alternative [57]. The pavement with the ash base was bid at

59.93 per sq. yd. wherein the crushed stone based pavement was $11.32. This

resulted in nearly 5100,000 in savings for the entire five mile job. Added to this direct savings was the avoided cost savings of about $90,000 which re-

sulted from the removal of 30,000 cubic yards of ash from the pond; a bid of

53.00 per cubic yard for removal of the bottom ash had been received.

Kinder [20] reports a cost comparison for cement treated bottom ash, cement treated crushed stone and untreated crushed stone base. Total cost/ mile (not including surface) for these three was $16,893, $30,261, and $41,096,

respectively. It can be seen that the cost is 40-50% of that for conventional materials.

Reference 31 presents detailed cost comparisons for the four alternate pavements shown in Figure 4.1, one of which contains a cement stabilized

flyash base. The cement stabilized flyash was more economical by 50.55 to

55.30 per square yard of pavement, compared to pavements with crushed stone,

full depth asphalt or a rigid, portland cement concrete layer.

2 6.70 / YD

BITUMINOUS WEAR SURFACE ON CEMENT - STABILIZED FLY ASH BASE COURSE

rev

Age 8.60 YD2

FULL DEPTH ASPHALT

Af Ai r . • is• fa• • •••• • P• • 0,•0o.O. o • . • s o 0 .;0. • • • le . • • • • 0 . h • o • .0.0 .b. •O• 06-• 0.0,0 ;'(.?.. •;013,..t.09);:e 090 • ••-00.- • • • •• ..'"?'•(::3;:<3,!rj :,0,e.; • • Li° • 7.25 YD2

BITUMINOUS WEAR SURFACE ON CRUSHED AGGREGATE BASE COURSE

2 12.00/ YD

REINFORCED CONCRETE ON CRUSHED AGGREGATE SUBBASE

Figure 4.1. Alternate Pavements Approximately Equivalent in Design Performance with Associated Initial Cost per Sq. Yard (Ref. 31).

91 In a recent proposal submitted to Georgia Power for a 174,000 sq. ft. parking area (6-inch thick bottom ash), the delivered price of bottom ash at

Plant Hatch was bid at $3.00 per cubic yard for the bottom ash plus $10.13 per ton for transportation (from Plant Harllee Branch). Added to this price would be the cost of Pozzalime ($43.00/ton delivered) and rental fee for a Seaman

Pulverizer ($2,000/week). Thus, the in-place cost of the stabilized bottom ash layer was about $3.90/yd 2 . However, this did not include base layer compaction or surfacing costs.

4.4 LIFE CYCLE COSTS - GENERAL CONSIDERATION

The total cost of providing a pavement to meet the demands of the users or the intended functions is composed of:

1. initial cost

2. maintenance cost (patching, overlays, etc.)

3. salvage value

4. time value of money (interest rate)

5. user costs (delays, vehicle damage, etc.)

This total cost is often termed LIFE CYCLE cost. It is an important concept

in pavement design and associated economic analyses. If only initial cost is considered, then a false picture of true economy might be obtained. For example, a pavement structure which requires extensive future maintenance may actually have a large life cycle cost even though its initial cost may be

low.

Thus, when considering the economics of using bottom ash materials in the pavement structure, not only must initial pavement cost be considered, but also the frequency and extent of future maintenance. Unfortunately, all too often this is not done; it is often difficult to predict future maintenance costs when many of the materials involved are new and/or unproven.

92 CHAPTER 5

ENVIRONMENTAL CONSIDERATIONS

5.1 GENERAL

In the process of obtaining samples of ponded ash and using ash materials in highway construction applications, there are certain environmental questions that may arise. Because some of these issues are not yet resolved, they are discussed here only briefly. Environmental concerns lend themselves to cate- gorization into one of two major subject areas.

5.2 EFFECTS OF REMOVING ASH FROM PONDS

One obvious question relates to the degree of disturbance as a result of dredging/digging activities that would take place as ash is recovered (from ponds) for utilization purposes. The concern here is not that the ash product would be affected but that the disturbance might lead to discharge permit violations. For instance, ash pond activity could possibly result in elevated levels of TSS (total suspended solids) or trace metals, as settled ash is resuspended or pockets of leachate in the ash deposits are disturbed.

Although these questions are deserving of consideration, it is likely that there would be little measureable effect that could be attributed to utilization activities. Utility representatives indicate that there is already as much dredging activity in the ponds as could be expected (at any one time) from ash reclamation. Current activities frequently involve displacing ash deposits in order to raise the dikes or distribute ash within or between ponds. In addition, many plants currently recycle ash pond effluent for ash sluicing, and, as a result, have an outfall (to other surface waters) only under emergency conditions.

93 5.3 CLASSIFICATION OF ASH IN REUSE APPLICATIONS

As a solid waste, utility ash is considered under the Resource Conserva- tion and Recovery Act. Before regulating wastes from utilities and other industries, Congress mandated that EPA conduct a detailed study of these wastes and their effect on the environment. In the meantime, high volume utility wastes have been granted a RCRA exemption until the EPA study is completed in early 1984.

One of the case study sites being used in the EPA evaluation of utility waste disposal practices is Gulf Power's Plant Lansing Smith. Results to date from this and other plants indicate that there are apparently no significant groundwater or surface water problems as a result of ash disposal practices.

Furthermore, EPA has indicated that it is likely that utility ash will be classified as non-hazardous from the federal perspective, with additional regulation left up to the discretion of the individual states.

The above comments apply to ash as it is disposed - in a pond (wet) or landfill (dry). However, ash utilization for highway construction will consider ash in a form where it should have even less contact with the environment. In most cases the ash would be treated with asphalt, lime or cement, effectively sealing it from any leaching mechanisms.

Kinder [44] states that all the state environmental agencies in the AEP service area have exempted ash reuse applications from all solid waste regula- tions. Furthermore, Warren [73] indicates that state agencies in the Southern

system's service area have given no indication so far that they intend to regulate reused ash at all.

In summary, while the above questions are still unresolved, there is ample reason for the utility industry to expect favorable outcomes.

94 CHAPTER 6

CONCLUSIONS AND RECOMMENDATIONS

6.1 GENERAL

Large quantities of crushed stone and other paving materials are used in the construction and maintenance of highways. In some areas of the southeast, particularly the coastal areas, there are shortages of conventional aggregate supplies. Utilization of existing aggregate supplies requires fairly large hauling distances and resultant high transportation costs.

Throughout the southeast highway agencies are continually seeking more economical materials and alternate supplies of aggregates and paving materials.

One heretofore largely overlooked source of highway construction material is the ash produced at coal-fired power plants. Relatively large quantities of power plant ash are currently being produced and even larger quantities are anticipated for the future. The Southern Company produces annually about 4.3 million tons of ash, including 0.8 million tons of bottom ash. Most of the ash is disposed of in ponds. Approximately 50 million tons of ash exists

in the various ash ponds of the Southern electric system.

The ash collected at typical coal-fired power plants is composed of about 75% to 85% flyash and 15% to 25% bottom ash (about 15% bottom ash in the Southern electric system), which is substantially coarser in texture.

Although two types of boiler bottom material can be generated, the plants

in the Southern system produce only "dry bottom ash."

The disposal of this "waste" material normally consists of placing it in ash ponds or landfills; some of the flyash and a smaller quantity of bottom ash are sold. The quality and characteristics of bottom ash have only recently become of concern at some isolated plant sites.

95 Some areas of the U.S., particularly West Virginia, are making extensive use of bottom ash. For many years the National Ash Association, the Uni- versity of West Virginia and more recently, the Federal Highway Administration have been involved in extensive evaluation and/or promotion of bottom ash for use in highways. However, there is not a wealth of technical information available concerning bottom ash. Very little documented information has been found concerning bottom ash produced by the Southern system.

6.2 ATTRACTIVENESS OF BOTTOM ASH USE

A primary reason that the use of bottom ash is attractive to the Southern

Company and its subsidiaries is related to (a) income from ash sales and

(b) avoidance of costs associated with future handling and disposal of ash materials.

The consumer, on the other hand, should be attracted to the use of bottom ash primarily because of the potential cost savings that might result. There is a concern for quality and good performance and a need to develop substantial technical data before predicting performance of bottom ash materials in a pavement environment. It is doubtful that highway agencies will promote the use of bottom ash unless specifications are developed and economics are attractive compared to conventional materials.

A contractor considering bottom ash as an alternative material will not be willing to tolerate the risk associated with a "new", unfamiliar material without a potentially greater profit.

One other attractive aspect of bottom ash is the good water resistance shown by asphalt mixes containing bottom ash. This is of particular interest in those areas using granite aggregates.

96 6.3 PROBLEMS AND UNCERTAINTIES ASSOCIATED WITH USE OF BOTTOM ASH

Based on the previous discussions of bottom ash in this report, there appear to be a number of problems and/or uncertainties associated with the utilization of bottom ash as a paving material in the general region encompassed by the Southern electric system. The following is a listing of the major problems and/or uncertainties:

1. Bottom Ash Materials

a. Variability of material is it exists in ponds, particularly with regard to gradation; ponds in which flyash and bottom ash are co-disposed are of particular concern.

b. Presence of pyrite in existing bottom ash deposits; especially a problem in asphalt mixes but may also create problems in other applications.

c. Lack of knowledge relative to the presence of bottom ash particles which are "popcorn" or loosely sintered flyash agglomera- tions.

d. Concern as to the ability of conventional aggregate test methods and quality criteria to properly ascertain the acceptability of bottom ash as a source of aggregate.

e. Potentially inadequate distribution of bottom ash supplies relative to demands; this could adversely affect cost incentive by increasing transportation costs.

f. Possibility that quantities are not sufficient to supply local demands.

2. Paving Materials Containing Bottom Ash

a. Lack of proven performance as a paving material.

b. Poor experiences and erratic experimental data developed in certain laboratory studies, particularly those of the Georgia De- partment of Transportation.

c. Lack of understanding as to the reasons many of the mixes evaluated in the Georgia DOT Laboratories did not exhibit substantial strengthening when treated with lime (especially by-product lime) or cement.

d. Lack of information as to engineering properties of various types of paving material (untreated, lime-treated, cement-treated, asphalt-treated).

97 e. Unfamiliarity of contractors with the use of such a material.

f. Apparent high demands for asphalt or cement in treated mixtures.

g. Problems in mixing of stabilizing agents with these materials because of their light weight.

h. Uncertainty as to volume stability or shrinkage cracking which cement or lime-treated bottom ash mixtures may exhibit.

i. Degradation of bottom ash particles during handling and construction.

j. Poor experiences with surface asphalt mixes made with some portion of bottom ash as the aggregate material, particularly when using bottom ash material that contains some pyrite particles.

k. Lack of specifications specifically addressing bottom ash materials and mixtures.

6.4 RECOMMENDATIONS

Based on the findings of this study, it appears that bottom ash produced in the Southern system has excellent potential for use in paving mixtures.

However, it appears there is a need to develop a substantial amount of information concerning:

I. Character of the existing and new bottom ash at the various power plant sites

2. Properties and characteristics of various paving mixtures contain ing bottom ash

3. Potential performance of bottom ash mixtures in typical pavement structures

4. Relative economics of bottom ash use compared to other conventional paving materials

It is recommended that further research should be pursued in order to develop the previous information. Specific objectives of this research would be:

I. Establish availability of bottom ash materials in terms of type, quantity, quality and the presence of restrictions (use agreements with orders).

98 2. Establish the character of the existing deposits of bottom ash which occur at the various power plant sites. Physical properties such as grain size distribution, abrasion resistance, and soundness should be established. Additionally, chemical properties such as pH, composition, and presence of deleterious or foreign materials must be examined. Variation of these properties with horizontal and vertical location, and between deposits, should be established.

3. Evaluate the significant engineering properties of various bottom ash mixtures. Experiences with the use of bottom ash as a paving material suggest that it can be used either in an untreated state as a graded aggregate base or in a treated state as a base or subbase course. In the untreated state, physical properties identified in Item 2 above are significant; however, CBR, shear strength, and repeated load characteristics (resilient modulus, rutting potential, degradation) are also important.

In the treated state, strength and durability properties for mixes with various types and amounts of treatment need evaluation. For example, cement, commercial and by-product lime, and asphalt are possible choices for treatment of bottom ash. For these treated mixes, strength (compressive, flexural), durability, fatigue, and volume stability properties are significant in order to establish potential performance characteristics.

4. Predict the performance of the various types of bottom ash mixtures. The VESYS(a) program can be used to examine the potential pavement performance of sections containing various types of bottom ash mixtures.

5. Establish layer coefficients. Based on the VESYS study, laboratory study, and other available information, layer coefficients can be established as a function of mixture type and quality to facilitate integration into typical flexible pavement design methods.

6. Develop specifications. Model specifications must be developed in order that promising bottom ash mixtures can be used with confidence. Specifications would include: methods of handling, processing, construction techniques, construction cut-off dates, etc.

7. Examine both current and future economics. The economics of using various types of bottom ash mixtures should be evaluated relative to other types of paving materials such as graded aggregate base, cement and asphalt treated aggregate, and other asphalt paving mixes.

A research program to address these various objectives will be developed in a separate document.

(a) VESYS - viscoelastic pavement analysis system which is a pavement analysis and performance prediction computer program developed by the Federal High- way Administration.

99 REFERENCES

1. Seals, Roger K., Moulton, Lyle K., and Ruth, B. E., "Bottom Ash: An Engineering Material", Journal, Soil Mechanics and Foundations Div., American Society of Civil Engineers, Vol. 98, No. SM4, April, 1972.

2. Majidazadeh, K. , , Bowowski, G., and El-Mitiny, R. N., "Power Plant Bottom Ash in Black Base and Bituminous Surfacing: State of the Art Report", Report No. FHWA-RD-78-146, Federal Highway Administration, July 1, 1977.

3. Moulton, L. K., "An Overview of Ash Utilization", Shortcourse Notes, Technology and Utilization of Power Plant Ash, West Virginia University, Aug. 15-17, 1977.

4. Moulton, L. K., Seals, R. K., and Anderson, D. A., "Utilization of Ash from Coal-Burning Power Plants in Highway Construction", Research Record 430, Highway Research Board, 1973.

5. Church, R. L., Weeter, D. W., and Davis, W. T., "Coal-Fired Power Plant Ash Utilization in the TVA Region", Environmental Protection Agency Re- port No. EPA-600/7-80-172, Oct., 1980.

6. Seals, R. K., "Properties of Bottom Ash/Boiler Slag and Flyash", Short- course Notes, Technology and Utilization of Power Plant Ash, West Virginia University, Aug. 15-17, 1977.

7. Babcock, A. W. and Faber, J. H., "Power Plant Aggregates for Highways of the Future", paper presented at First FCP Research Progress Review, U. S. Dept. of Transp., Fed. Hwy. Adm., Sept. 17-20, 1973.

8. The Resource Recovery and Utilization Technical Committee and Envirosphere Company, "Electric Utility Coal Combustion By-Products: A Resource for Recovery and Utilization", Sept. 1981.

9. Rose, J., Lowe, J. A., and Floyd, R. K., "Composition and Properties of Kentucky Power Plant Ash", Proceedings, Fifth International Ash Utiliza- tion Symposium, Atlanta, Ga., Feb. 25-27, 1979.

10. Lechnick, W., Lin, A. L., Humphrey, A. J., and Dzurinko, T., "Determina- tion of Ash-Water Retention Time and Mixing Characteristics of Fly Ash Ponds", Proceedings, Fifth International Ash Utilization Symposium, Atlanta, Ga., Feb. 25-27, 1979.

11. Dzurinkol, E. W., and Lin, A. C., "Field Retention Time Studies of Ash Settling Ponds", Proceedings, Fifth International Ash Utilization Sym- posium, Atlanta, Ga., Feb. 25-27, 1979.

12. Head, W. J., and Seals, R. K., "Design and Construction of Experimental Haul Road and Parking Lot Facilities Utilizing Power Plant Ash", Pro- ceedings, Fifth International Ash Utilization Symposium, Atlanta, Ga., Feb. 25-27, 1979.

100 13. Kraft, D. C., Rozelle, J., Hawk, T., and Johnson, D., "Ash Utilization in Bikeway Construction", Proceedings, Fifth International Ash Utiliza- tion Symposium, Atlanta, Ga., Feb. 25-27, 1979.

14. Culley, R. W., and Smail, D. H., "Performance of Waste Coal Ash as High- way Subbase Course", Proceedings, Fifth International Ash Utilization Symposium, Atlanta, Ga., Feb. 25-27, 1979.

15. Salow, G., "Fly Ash/Boiler Slag Road Bases", Proceedings, Fifth Inter- national Ash Utilization Symposium, Atlanta, Ga., Feb. 25-27, 1979.

16. Majidzadeh, K., Bokowski, G., and El-Mitiny, R., "Material Character- istics of Power Plant Bottom Ashes and Their Performance in Bituminous Mixtures: A Laboratory Investigation", Proceedings, Fifth International Ash Utilization Symposium, Atlanta, Ga., Feb. 25-27, 1979.

17. Majidzadeh, K., Bokowski, G., and El-Mitiny, R., "Power Plant Bottom Ash in Black Base and Bituminous Surfacing, Volume 2: User's Manual", Report No. FHWA-RD-78-148, Federal Highway Administration, June, 1977.

18. Neumann, E. S., "Economics of Ash Transportation and Utilization", Short- course Notes, Technology and Utilization of Power Plant Ash, West Virginia University, Aug. 15-17, 1977.

19. Jones, D. A., "Potential of Bottom Ash", unpublished paper, Ash Management Systems, Inc., Atlanta, Georgia.

20. Kinder, D. L., "Cement-Stabilized Bottom Ash Base and Subbase Courses", Proceedings, Technology and Utilization of Power Plant Ash Symposium, Tempe, Arizona, 1978.

21. Majidzadeh, K., and Bokowski, G., "Bottom Ash Use in Black Base and Bituminous Surfacing", Proceedings, Fourth International Ash Utilization Symposium, St. Louis, Mo., March 24-25, 1976.

22. Usmen, M., and Anderson, D. A., "Use of Power Plant Aggregate in Asphal- tic Concrete", Proceedings, Fourth International Ash Utilization Sym- posium, St. Louis, Mo., March 24-25, 1976.

23. Meyers, J. F., Kapples, B. S., and DiGioia, A. M., Jr., "Guide for the Design and Construction of Cement-Stabilized Flyash Pavements", Pro- ceedings, Fourth International Ash Utilization Symposium, St. Louis, Mo., March 24-25, 1976.

24. Morrison, R. E., "Power Plant Ash: A New Mineral Resource", Proceedings, Fourth International Ash Utilization Symposium, St. Louis, Mo., March 24- 25, 1976.

25. Clayton, G. K., "Low Cost Pavements Utilizing Power Plant Ash", Pro- ceedings, Fourth International Ash Utilization Symposium, St. Louis, Mo., March 24-25, 1976.

26. Frascino, P. J., and Vail, D. L., "Utility Ash Disposal: State of the Art", Proceedings, Fourth International Ash Utilization Symposium, St. Louis, Mo., March 24-25, 1976.

101 27. Thompson, C. M., and Jones, B. F., "Determination of Hazardousness of Reuse Products Utilizing Low-Rank Western Coal Flyash/Bottom Ash", Final Report (Preliminary Draft), Contract No. DEAC1880FC10229, U. S. Department of Energy, August, 1981.

28. Miller, R. H., and Collins, R. J., "Waste Materials as Potential Re- placements for Highway Aggregates", Report 166, National Coop. Hwy. Res. Program, Transportation Research Board, 1976.

29. Colony, D. C., "Industrial Waste Products in Pavements: Potential for Energy Conservation", Transp. Research Record 734, Transp. Research Board, 1979.

30. Faber, J. H., and DiGioia, A. M., Jr., "Use of Ash in Embankment Con- struction", Transp. Research Record 593, Transp. Res. Board, 1976.

31. Guide for the Design and Construction of Cement Stabilized Flyash Pave- ments, Ash at Work, Process and Technical Data prepared by GAI Con- sultants, published by National Ash Association.

32. Anderson, D. A., "Bottom Ash as a Construction Material", paper prepared for Technology and Utilization of Power Plant Ash, Arizona State Uni- versity, Tempe, Arizona, Nov. 27-29, 1978.

33. Anderson, D. A., Usmen, M., and Moulton, L. K., "Use of Power Plant Aggregate in Bituminous Construction", Transp. Res. Record 595, Transp Res. Board, 1976.

34. Santhanam, C. J., Lunt, R. R., et al., "Waste and Water Management for Conventional Coal Combustion Assessment Report -- 1979; Volume IV, Utilization of FGC Wastes", Report No. EPA-600/7-80-012d, EPA, Office of Research and Development, Industrial Environmental Research Laboratory, March, 1980.

35. Theis, T. L., and Richter, R. 0., "Chemical Speciation of Heavy Metals in Power Plant Ash Pond Leachate", Vol. 13, Number 2, February, 1979.

36. Moulton, L, K., "Bottom Ash and Boiler Slag", Proceedings, Third Inter- national Ash Utilization Symposium, Pittsburgh, Penn., March 13-14, 1973.

37. Blocker, W. V., Morrison, R. E., Morton, W. E., Babcock, A. N., "Marketing Power Plant Aggregaces as a Road Base Material", Proceedings, Third In- ternational Ash Utilization Symposium, Pittsburgh, Penn., March 13-14, 1973

38. Raymond, S., and Smith, P. H., "The Use of Stabilized Flyash in Road Construction", Civil Engineering and Public Works Review, Jan. 1964.

39. Styron, R. W., "Bottom Ash Lightweight Aggregate", Proceedings, Fifth International Ash Utilization Symposium, Atlanta, Ga., February 25-27, 1979.

40. Shuler, T. S., "The Effects of Bottom Ash Upon Bituminous Sand Mixtures", Final Report, Joint Highway Research Project, JHRP-76-11, March 16, 1976.

102 41. Organization for Economic Co-Operation and Development, "Use of Waste Materials and By-Products in Road Construction", OECD Research Report, Paris, France, 1977.

42. Sikes, P. G., and Kolbeck, H. J., "Disposal and Uses of Power Plant Ash in Urban Areas", Journal of the Power Division, Am. Soc. of Civil Engrs., Vol. 99, No. P01, May, 1973.

43. Usmen, M., Anderson, D. A., and Moulton, L. K., "Applicability of Con- ventional Test Methods and Material Specifications to Coal-Associated Waste Aggregates", Transp. Res. Record 691, Transportation Research Board, 1978.

44. Kinder, Dennis, Ash Utilization and Research Engineer, American Electric Power Service Corporation, private communication, October, 1982.

45. Faber, J. H., "A U. S. Overview of Ash Production and Utilization", Proceedings, Fifth International Ash Utilization Symposium, Atlanta, Ga., Feb. 25-27, 1979.

46. Covey, J. N., Executive Vice President, National Ash Association, Wash- ington, D.C., private communication, July, 1982.

47. "The Application of Flyash from Brown Coal for Road Base Courses", Polish Ministry of Transport, Road and Bridge Research Institute, Warsaw, 1976. (Project developed under Agreement No. 3 concluded between the U.S. Dept. of Transp. and the Polish Ministry of Transp. on Oct. 17, 1974).

48. Webb, William M., Georgia Department of Transportation, Geotechnical Materials Laboratory, Forest Park, Ga., unpublished laboratory data and evaluation reports.

49. First International Ash Utilization Symposium, Pittsburgh, Pa., 1957.

50. Second International Ash Utilization Symposium, Pittsburgh, Pa., 1970.

51. Third International Ash Utilization Symposium, Pittsburgh, Pa., 1973.

52. Fourth International Ash Utilization Symposium, Pittsburgh, Pa., 1976.

53. Fifth International Ash Utilization Symposium, Atlanta, Ga., 1979.

54. Sixth International Ash Utilization Symposium, Reno, Nevada, 1982.

55. Marek, et al., "Promising Replacements for Conventional Aggregates for Highway Use", Report 135, National Coop. Hwy. Research Program, Transp. Res. Board, 1972.

56. Styron, R. W., private communication, Ash Technology, Marietta, Ga., 1982.

57. Rachford, J. R., "Report on the Georgia Power Company's Use of Lime Treated Bottom Ash and Flyash as a Pavement Base Material", unpublished report, Georgia Power Company, June, 1982.

103 58. Barenberg, E. J., and Thompson, M. R., "Design, Construction, and Per- formance of Lime, Flyash, and Slag Pavement", Trans. Res. Record 839, Trans. Res. Board, 1982.

59. Shuler, T. S., and Wood, L. E., "The Effects of Bottom Ash Upon Bitumi- nous Sand Mixtures", Proceedings, Assoc. of Asph. Paving Technologists, Vol. 46, 1977.

60. AASHO, "AASHO Interim Guide for Design of Pavement Structures - 1972", Washington, D.C., 1972.

61. ENR - "Billions at Stake in Coal Waste Fight", Vol. 204, No. 2, Jan. 10, 1980.

62. Pavement Design Guide, Georgia Department of Transportation, 1982.

63. Ron Edmanson, Engineer, Georgia Department of Transportation, private communication, July, 1982.

64. William Gartner, District Engineer, The Asphalt Institute, Tallahassee, Florida, private communication, 1982.

65. Majidzadeh, K., Bokowski, G., and El-Mitiny, R. N., "Power Plant Bottom Ash in Black Base and Bituminous Surfacing - Vol. 1 - Laboratory Investi- gation Results, Report No. FHWA-RD-78-147, Federal Highway Administra- tion, December, 1977.

66. "Upgrading Low Quality Aggregates for PCC and Bituminous Pavements", Report 207, National Cooperative Highway Research Program, Trans. Res. Board, 1979.

67. Recycling Materials for Highways, Synthesis of Highway Practice Report 54, Nat. Coop. Hwy. Res. Program, Trans. Res. Board, 1978.

68. FCP Annual Progress Report, Federal Highway Administration, March, 1981.

69. "Extending Aggregate Resources", Special Technical Publication 774, Am. Society for Testing and Materials, 1982.

70. Ratcliffe, D. M., Georgia Power Company, private communication, July, 1982.

71. Ratcliffe, D. M., Georgia Power Company, private communication, Sept., 1982.

72. Fuller, W. B. and Thompson, S. E., "The Laws of Proportioning Concrete," Transactions, American Society of Civil Engineers, Vol. 59, 1907.

73. Warren, D. H., Environmental Licensing Department, Southern Company Services, private communications, November, 1982.

104 APPENDIX A

USE OF POWER PLANT BOTTOM ASH IN BLACK BASES AND BITUMINOUS SURFACING (Taken from Majidzadeh, et al. [17])

• RECOMMENDED GUIDELINES

RECOMMENDED LABORATORY TESTING PROCEDURES

• RECOMMENDATIONS FOR IMPLEMENTATION AND FURTHER RESEARCH RECOMMENDED GUIDELINES

Source Selection

The engineering and physical properties of bottom ashes vary considerably, depending upon plant type, coal source and type, coal burning methods, and ash production and stockpiling methods.

If wider utilization of these materials is expected, bottom ashes must be regarded by power-generating companies as an engineering material rather than as a waste and as such, it is strongly recommended that material suppliers exercise stronger controls over production, collection and stockpiling of these materials to preserve material integrity and provide a product of greater uniformity. It is also recommended that material suppliers be able to provide more specific data on the chemical and physical characteristics of their materials, such as gradation, specific gravity, density and chemical composition, to enhance consumer choices.

One of the greatest concerns to potential consumers at this time is the non-uniformity of these materials which result in variations not only from one plant to another but often within the same plant. Material suppliers should be able to document the degree of non-uniformity and attempt to bring material variability to within reasonable levels acceptable to state departments of transportation and consumers.

A-2 In selecting sources of these materials, the following factors should be considered by consumers:

1. Adequate supplies of the same (or comparable) material from the supplier should be available for the duration of the construction project, In one West Virginia project, the initial pavement design had to be substantially revised prior to construction when the power plant shut down and could not provide adequate supplies of the intended ash. Such incidents could result in costly delays and discourage future reliance on a supplier and/or the material itself.

2. The cost of bottom ash material, including costs of transportation, material handling and storage, sorting and sizing efforts, etc., should not exceed the costs of using a comparable conventional aggregate.

3, Consumers may reject material that has been stockpiled in such a way as to affect material quality, such as being combined with fly ashes or substantial amounts of pyrites and sulfates or in such a manner that the fine and coarse fractions of the material have been badly segregated, unless these factors are not significant for the intended use.

From the results of evaluations of these materials selected from various plants around the United States, the majority received in this study could be considered suitable for use in highway construction.

Material Selection

Bottom ash materials, classified either as dry bottom ash or wet bottom ash, are being produced and are available in sufficient quantities and sizes suitable for most highway applications. Dry bottom ashes, as produced, can be used to meet specification requirements for aggregate base courses, asphaltic concrete base courses, asphaltic concrete binders and leveling courses, as well as surface course applications, To meet the specification requirements for high quality paving mixtures, in some instances, suitable blends of dry bottom ash with conventional agg -regates should be prepared and tested for compliance with performance requirements. Wet bottom ash, on the other hand, usually must be blended with conventional aggregates, dry bottom ash or fly ash in order to attain adequate stability under load.

A - 3 The criteria used for evaluating and accepting or rejecting a given bottom ash material fall into two categories: (1) specification requirements for bottom ash as an aggregate; and (2) specifications for bituminous mixtures incorporating bottom ash as an aggregate.

.At this time, no standard procedures have been designed specifically for the evaluation and acceptnuce or rejection of bottom ash as an aggregate, although research has indicated that most bottom ashes can meet standard testing specifications for conventional aggregates. In recent years, there has been considerable debate over the pros and cons of applying some standard tests, such as sodium sulfate soundness and Los Angeles abrasion tests, to all bottom ash materials. Furthermore, these procedures have also been criticized when applied to conventional aggregates in that such tests may not realistically evaluate the durability and soundness of any aggregate. Future research may indicate that due to the unique properties of bottom ashes, the results of these tests may he, for all practical purposes, meaningless in evaluating the quality and predicting the performance of these materials.

However, until such time as it has been determined whether these standard testing methods are or are not applicable to bottom ashes and other aggregates, and until such time as laboratory procedures can be designed specifically for these materials and verified, it is recommended that the following test requirements, based on the current state of knowledge of aggregate characterization, be used in the evaluation of bottom ash materials.

Recommended Test Prearam

In the flow chart presented in Figure A-1., the recommended testing program for bottom ash and ash-asphalt mixture evaluations are diagrammed. This program includes:

1. Selection of Preliminary Data from Ash Sources

(a) Ash composition (b) Approximate gradation (c) Test data, if available, on specific gravity, density, etc. (d) Material production uniformity or variability due to source.

0 Aggregate Acceptance Testing

(a) Gradation (b) Specific gravity (c) Unit weight or density

A-4 OBTAIN PRELIME,TARY SOURCE DATA

AGGREGATE SCREENING TESTS

iFre: Gradation 1So. Gra%-ity Density LA Abrasion Soundness Modulus 1

=TITRE ACCEPTANCE TESTING 1 'vlarshall Mix Design Durability Performance Indicators

Op, Asphalt Content Immersion-Compression Modulus of Resilience

Ash/Aggregate Ratio Saturation and Fatigue Freeze-and-Thaw Aggregate Degradation Fracture Toughness

Ruttin,c:

Figure A-1. Recommended Test Program Flow Chart

A-5

Los Angeles abrasion Sodium sulfate soundness Modulus of resilience Freeze-and-thaw conditioning and/or British crushing test

3. Mixi:ure Acceptance Testing

(a) Marshall mix design (b) Optimum asphalt content (c) Optimum ash; aggregate composition (d) Aggregate degradation potential

Durability Acceptance Testing

(a) Immersion-compression tests (b) Saturation and freeze-and-thaw tests

5. Mixture Performance Indicators

(a) Modulus of resilience (b) Fracture toughness (c) Fatigue . (d) Rutting

Material Acceptance Criteria

In general, since bottom ashes have been shown to be comparable to conventional aggregates insofar as their engineering properties are concerned, many of the criteria for acceptance of a conventional aggregate may be applied to these materials as well, except where field and laboratory data indicate that bottom ashes will perform satisfactorily even thi^ough they may not meet specification requirements.

As_rzre ,zate Acceptance

The gradations of bottom ash materials range in size distribution from gravel to sand and generally meet gradation requirements for base course, asphaltic concrete base course and binder and surface course mixtures. Dry bottom ash has a wider range in grain size distribution and can often be used as received from the supplier or with minimal scalping or sizing efforts whereas wet bottom ash tends to be a one-sized aggregate, lacking in coarse fractions, and usually must be blended with other aggregates. The acceptance criteria for bottom ash gradation are the same as for conventional aggregate and for specific job requirements, except that one should take into consideration the variability in this material due to production and handling methods. The specific gravity of bottom ash is an indication of the material's density and is influenced by such factors as coal type and composition, coal burning methods, etc. The specific gravity of most dry bottom ashes ranges from 2.0 to 2.4, while this property for wet bottom ashes ranges from about 2.60 to 2.80. The acceptance criteria for specific gravity of bottom ashes are the same as for conventional aggregates. It is also recommended that the minimum acceptance limit for bottom ash unit weights be not less than 70 lbs/ft 3 (1121.4 3 kg/m ), which is the same as-for conventional aggregates.

The Los Angeles abrasion test is a widely used and generally specified procedure originally designed to identify low quality aggregate for road construction. The use of this test has been criticized, as previously discussed, on the grounds that the values obtained are often arbitrary and may have little relevance to actual aggregate properties or performance characteristics. However, re- sea-ch has shown that bottom ashes generally can meet specification limits and as an acceptance criterion, it is recommended that the abrasion of bottom ash materials be limited to 40 percent or less.

The sodium sulfate soundness test has been similarly criticized but it is still common practice to use it in evaluation of aggregates. In view of the data previously discussed that raises serious questions about the applicability of this test to bottom ash materials, particularly wet bottom ashes which may show high soundness losses due to the high internal stresses of the material rather than expansion of the sodium sulfate, it is recommended that this procedure be considered a secondary screening test, with limits of 10 and 20. percent soundness loss being the limits for surface and base course applications respectively.

Although freeze-and-thaw testing to simulate environmental conditioning and crushing tests, such as the British crushing test, are not yet well recognized by most transportation agencies, these tests could be used as supplemental procedures to further assess aggregate quality, However, any recommenda- tion for the incorporation of these tests into use specification's would be premature at this time.

Another major aggregate characterization test is the evaluation of resilient modulus using triaxial loading conditions. This procedure, although well recognized by many researchers, has not yet been fully implemented by various transportation agencies. However, if in the future, this procedure is specified for conventional aggregates, it could be similarly applied to bottom ash aggregates as well.

Mixture Desic.-n and Durabili tv

As a result of the laboratory data generated in this investigation, it is recommended that Marshall mix design criteria be used for the design of mixtures using bottom ash aggregate. The preparation of Marshall test SDECir:IL::::

A- 7 may be conducted using drop hammer (Marshall) compaction, gyratory or kneading compaction. For bottom ash materials showing little degradation under load, the method of specimen compaction may not be an important test variable. However, since research has indicated that compaction method has a significant effect upon stability, density and other properties of mixtures using this aggregate, it is strongly recommended that the test program include an evaluation of compaction method, particularly for those ash aggregates suspected of degradation under loading. For these aggregate mixtures, the use of kneading or gyratory compaction may be more representative of field compaction processes and might predict more accurately the performance of such mixtures under field compaction.

The Marshall mix design criteria involving measurement of air voids content, density, flow, stability, voids in mineral aggregate and voids filled with asphalt should be the same as procedures used in the design of conventional mixtures.

In bituminous mixtures prepared with bottom ashes, the optimum asphalt content, as determined from Marshall testing, may be selected using similar criteria to those applied to conventional aggregate mixtures. However, in determining optiMum asphalt content of these mixtures, one should also consider the following research results:

1. Optimum asphalt content is related to the amount of ash used in the mixture, and decreases as the ash content is decreased. It is also influenced by compaction method, decreasing somewhat when kneading or gyratory compaction is used.

2. It appears that beyond a certain "threshhold" level of ash in the mixture, stability is not significantly dependent on ash content. The introduction of bottom ash up to 30 percent reduced the stability somewhat in this study, but at higher ash contents, stability remained relatively unchanged. This observation is of great practical significance since it makes it possible to prepare satisfactory bituminous mixtures meeting mixture stability requirements.

3. Although the optimum asphalt content for ash-asphalt mixtures tends to be much higher than for conventional blends, it is possible to reduce asphalt content without sacrificing mixture stability, which for these type of mixtures appears relatively insensitive to asphalt content.

A-8 4. Asphalt content does affect air voids content and VMA in ash-asphalt mixtures as in conventional mixtures. How- ever, the amount of ash used in these mixtures will also affect mixture density, air voids and VMA.

5. Economical mixtures, comparable to conventional aggregate mixtures, can be prepared by reducing the asphalt content below the optimum, sacrificing some stability but most significantly, by increasing the percent air voids to as much as 10 to 15 percent. Such mixtures are acceptable as base course or binder course, where this property is of less significance to mixture durability.

6. Because dry bottom ash is more absorptive to asphalt and usually less dense than conventional aggregates, Anderson (9) has suggested that asphalt content should be based upon volume rather than unit weight. On that basis, a bottom ash at 110 lbs/ft 3 (1762 kg/m3) at 9 percent asphalt content might be comparable to a conventional aggregate at 7 percent asphalt and 140 lbs/ft 3 (2243 kg/m 3),

Optimum ash-aggregate-asphalt composition should be selected using the same criteria as for conventional aggregates. Research indicates that depending upon the ash properties and job requirements, mixes of acceptable stability and durability can be designed using 100 percent bottom ash or blends of ash and conventional aggregates in various increments. For wet bottom ash, however, as a rule, mixtures should contain no more than 50 percent wet bottom ash.

The standard procedure for evaluating bituminous mixture durability is the immersion-compression test. An additional durability test was employed in this investigation employing specimen saturation and freeze-and- thaw conditioning to simulate environmental conditioning. It is recommended that the immersion-compression test constitute one of the acceptance criteria and it is also strongly recommended that both saturation and freeze-and-thaw conditioning be implemented as durability testing. These criteria may provide highly useful information since the results of these tests as conducted in this investigation indicated that immersion and saturation, and in some instances, even freeze-and-thaw cycling actually increased the strength of these mixtures. The mechanisms underlying this phenomenon are not understood and clearly need additional research.

It is also useful to conduct saturation and freeze-and-thaw conditioning when employing supplementary quality tests such as modulus of resilience. indirect tensile strength, etc.

A-9 Mixture P°1-forrnance

The design and performance specifications currently employed by most highway departments rarely include any criteria for acceptable levels of such performance variables as mixture moduli, fatigue and fracture resistance, etc.

The modulus of resilience is a highly important material variable required for the development of pavement layer equivalency, pavement thickness and remaining life analyses. Although the use of this performance parameter is not vet universally accepted by highway departments, it is strongly recommended that the test procedure for evaluating modulus of resilience be implemented for both conventional aggregates and bottom ash aggregate mixtures. The results of this investigation indicate that suitable bottom ash mixtures could be prepared having modulus of elasticity, or modulus of resilience, values falling within an acceptable range of 150,000 to 400,000 psi The resilient modulus of bottom ash mixtures, depending upon percent ash in the mix and asphalt content, tend to be lower than those for conventional mixtures. However, the data imply that pavement systems of equivalent structural performance levels could be prepared utilizing the concept of •mixture layer equivalency.

The use of fatigue and fracture criteria for the design of bituminous mixtures is similarly a fairly new concept and has not yet been fully implemented on a national basis. The results of this study have indicated that fatigue and fracture test requirements are applicable . to both conventional aggregate and bOttom ash mixtures. However, due to a higher asphalt content, lower stability and higher air voids content of bottom ash mixtures, the potential for mixture rutting is significantly higher than for mixtures using conventional materials. Therefore, the mixture design optimization and pavement design should also consider setting allowable limits for mixture rutting under repeated loading. These limits might be set similar to conventional mix requirements and depend on use specifications.

RECOMMENDED LABORATORY TESTLNG PROCEDURES

In the previous section of this report, recommendations for the development of user guidelines and specification criteria for the use of bottom ashes in bituminous mixtures were discussed. The recommended testing program for the evaluation of these materials includes not only testing procedures that are standard and often required for conventional aggregates, but also certain supplemental procedures (modulus of resilience, fatigue and fracture tests, saturation and freeze-and-thaw conditioning, etc.) were recommended as well, since this investigation and others have found such procedures useful in providing valuable information on aggregate and mixture stability, durability and performance potential.

A-10 In the following section; the testing procedures recommended for these materials will be discussed. Those procedures which are standard and well- known will not be discussed in depth since it is assumed that the reader is familiar with such tests, Those procedures that are recommended as supplemental testing criteria and shall be conducted at the discretion of the consumer will be discussed in more detail and sources of further information will be cited for the reader's convenience.

Aggregate Testing

Shape and surface texture; which will affect air voids and asphalt contents as well as indicate whether problems with aggregate interlock-might be anticipated, can be ascertained through the use of SEMI microphotography methods. As a rule, more porous ashes will absorb more water and asphalt and ash samples containing large amounts of friable particles may well be susceptible to degradation under compaction and loading.

Gradation data, in addition to that provided by the material supplier, should be obtained using AASHTO T27 and ASTM C136 standard methods. The coefficient of uniformity, which is an indicator of material variability, should be calculated using the following formula: D69 C u D 10 where C u is the uniformity coefficient D is the grain diameter at 60 percent passing 60 D 1 0 is the grain diameter at 10 percent passing

Specific gravity and water absorption characteristics should be obtained using AASHTO TS4 and ASTM C12S methods for fine aggregate and AASI-[TO TS5 and ASTM C127 methods for coarse aggTegates. Both fine and coarse fractions of these materials should be tested. Since specific gravity is a measure of ash density, it might be considered an indicator of material soundness. However, it should be noted that a less dense ash with a high ferric oxide content may yield a higher specific gravity than its density would indicate.

Chemical composition of these materials can be determined using x-ray diffraction or other standard analysis procedures, It is important to ascertain the levels of ferric oxide, pyrites and sulfates present in the ash, as these constituents have been known to affect material behavior in bituminous mixtures. For comparison purposes, the reader may wish to consult the state-of-the-art report (6) in which chemical analyses of numerous coal ashes were presented in tabular form.

A - 11 Unit weights are to be determined using A.ASETO T19 and ASTM C29 methods. Maximum unit weight is obtained using the rodding procedure while minimum unit weight is determined using the shoveling procedure. Void ratios are obtained using AASHTO T20 and ASTM 030 methods.

Although the Los Angeles abrasion test may not be an accurate predictor of aggregate durability, as previously discussed, it is generally specified and should be conducted accortli.ng to .A.\SHTO T96 and ASTM 0131 methods, except that cue must modify the test to include fines since the above specifications are for coarse aggi-egates.

Sodium sulfate soundness testing, as specified in AASHTO T104 and ASTM CSS, has been severely criticized in its application to bottom ash materials and in the recommended testing program, this is considered a secondary screening test. Ash samples should be divided into fine and coarse fractions and tested separately under a minimum of five cycles°

Sund-mr -Itary Procedures

Although not required and not yet universally accepted by most highway departments for the evaluation of conventional aggregates, freeze-and-thaw conditioning and modulus of resilience testing under tria:tal loading may provide additional and highly valuable information regarding aggregate quality and susceptibility to environmental conditions. These procedures will be discussed in some detail in the section on mixture testing.

It is also recommended that a comparison of compaction method be used in these materials, since this procedure has been known to affect aggregate behavior. Moisture-density relationships should be determined using both drop hammer and gyratory or kneading compaction. This is particularly important when testing dry bottom ashes with friable particles that may be susceptible to degradation under loading. It is recommended that a minimum of three samples be subjected to each of the following tests:

Dron-Hammer Comnaction

A Harvard Miniature Compaction Device can be used and the procedure for preparing and compacting the samples are conducted according to Method C of AASHTO T99 and ASTM C98 standard methods. In this study, a mold four inches in diameter and 5 inches in height (10.16 ern by 12.7 cm) was used and materials coarser than passing a 3/4 inch (1.9 cm) sieve size were discarded. Each sample was compacted in three layers with 47 blows applied per layer, a total compaction energy of 56,300 lb/ft' (2.7 x 10 6 J/m 3). New material should be used for each specimen to avoid the effects of disintegration under compaction.

A- 12 Gyratory Compaction

In this method, the principle variables controlling compaction energy are axial compressive load, angle of gyration and the number of gyrations. In this study, a compactor built at Ohio State University was used. The angle of gyration was set at two degrees, 15 gyrations were used and a compressive load of 1000 lbs. (455 kg) was applied.

The compactor imparts a static axial compression load and a Id -leading. or shearing type of lcad due to the gyratory angle, which results in the eccentric application of axial pressure under gyration. The desired number of gyrations is preset by means of a counter and the angle of gyration is adjustable by moving two horizontal plates relative to each other. The axial compression load is applied by means of a high pressure jack and can be maintained constant during the test. The magnitude of the load is measured by a dial gauge attached to a proving ring.

The bottom ash sample is mixed with water and placed in the gyratory compactor mold, which measures four inches (10.16 cm) in internal diameter and five inches (12.7 cm) in height. After the desired number of gyrations are applied, the angle is returned to zero and the sample is allowed to stand under a constant axial leveling load for one minute.

The moisture contents and corresponding dry densities can then be calculated using standard methods and the results compared to assess the effects of compaction.

Mixture Testing

It is recommended that Marshall mix design procedures be used to prepare bottom ash-bituminous mixtures. The Marshall mix design analyses are conducted according to ASTM D1559 methods. Marshall test specimens are prepared by preheating the aggregates for at least two hours at 300°F (149tC); the asphalt is also heated to the same temperature. The aggregates are then mixed with the asphalt and compaction, using drop hammer (Marshall) compaction methods, is begunat temperatures ranging from 250 to 275°F (121 to 135°C). It is recommended that a minimum of four asphalt contents be used and a minimum of three Marshall specimens be prepared at each asphalt content to determine optimum asphalt content using Marshall criteria (stability, density, flow and voids analyses). If supplemental testing such as modulus of resilience, fracture toughness, indirect tensile strength, etc., is to be done, a minimum of three additional specimens at each asphalt content should be prepared for each additional procedure.

A- 13 For mixture design testing, a minimum of three (and preferably four) mixes should be designed using incremental ash contents of, say, 30, 50, 70 and 100 percent dry bottom ash or 30, 45, 60 and 75 percent wet bottom, ash (unless it is an exceptional ash, experience indicates that mi_xures using 100 percent wet bottom ash will yield unsatisfactory results). These mixtures should be designed using three asphalt contents -- optimum, +1 percent of optimum and -1 percent of optimum. A minimum of three Marshall specimens should be prepared for each ash content at each asphalt content for Marshall testing. To evaluate the effects of compaction and to predict the degradation potential of the aggregate mixture, an additional three specimens at each ash content for each asphalt content should be prepared using 1meading or gyratory , compaction. These specimens are then subjected to Marshall testing.

By designing various mixes at different ash contents and testing them at selected asphalt contents, the optimum asphalt content can be determined by Marshall criteria and the variations in Marshall properties due to ash and as-: phalt content variations may be ascertained, which will facilitate the selection . of a final mix design that meets job requirements.

The user may also wish to vary the type of conventional aggregate -- such as crushed gravel, riv.er sand or limestone sand -- to determine what effect the choice of conventional aggregates might have on mixture performance. As previously mentioned, this variable may be more significant when designing mixtures using wet bottom ash,

In the immersion-compression durability test, conducted in accordance with AASI-ITO D1074 and ASTM D1075 methods, a minimum of three samples four inches (10.16 cm) in diameter and height are prepared at three or four asphalt contents (asphalt contents of 6, 8, 10 and 12 percent were used in this investigation).

The specimens are first tested under an FITS (Material Testing System) device in a dry condition at room temperature (77°F or 25°C) at a uniform rate of vertical deformation (0.2 inch or .508 cm.was used in this . study). The comH pressive strength of the specimen can be calculated by dividing the maximum vertical load by the original specimen cross-sectional area. To assess the effect of water on mixture cohesion, specimens are immersed in water for 24 hours at 140 +_ 1. S°F (60 + 1°C), then transferred to another water bath maintained at 77.4- 1.8°F (25 4- 1°C) for two hours and then tested as above. The compressive strengths of the immersed samples are then determined and the relationship between mixture strength before immersion and strength after immersion can be compared using the following formula:

Sr) Index of resistance to moisture = x 100 S1 In the above formula, s 2 is the compressive strength of the immersed specimen while S 1 is the compressive strength of the dry specimen. As an example, in this study a dry bottom ash sample tested in the dry condition yielded a compressive strength of 180 psi and the sample after immersion had a compressive strength of 337 psi. Using the above formula, • 3'3'7 Index of resistance = 180 x 100 = 187%

This figure reflects. an E,I. CREASE in. mixture strength after immersion, which is conSistant with other results obtained in this investigation.

In view of the apparent tendency of these mixtures to increase in strength after saturation and to assess the possible effects of environmental conditions, it is strongly recommended that the following procedures be conducted on triplicate specimens.

Saturation

After first determining the strength of the specimens in the dry condition, using modulus of resilience, indirect tensile strength or similar procedures, the Marshall specimens are immersed in a water-filled jar. A vacuum is then applied to the jar for about 30 minutes and the jar is shaken periodically to force the air out of the specimens and allow the water to fill the voids, The specimens are then allowed to set under water at atmospheric pressure for another 30 minutes. The samples are then removed from the jar and placed in a water batch at 77°F (25°C) for two hours, and then retested for strength, modulus or other desired properties.

Freeze-and-thaw

The equipment used to generate freeze and thaw cycles going from 0 to 120 to 0°F (-18 to 49 to -18°C) should be set to achieve one full freeze-thaw cycle in about six hours. In this study, eighteen full freeze-and-thaw cycles were used to condition the specimens, which were prepared in triplicate and saturated using the above procedure.

The saturated specimens are placed in plastic bags containing some water and then placed in another plastic bag with a zipper lock. Each specimen is then wrapped in aluminum foil and placed in the adjusted freeze and thaw apparatus, where it is subjected to the selected number of freeze-tha'.v cycles. The specimens are then removed from the machine, the foil and plastic bags are removed, and the specimens are then kept at 77°F (25°C) for about two hours. They may then he subjected to the desired procedure to measure change in - durability after conditioning.

A- 15 Sunolemental Procedures

Modulus of Resilience

The resilient modulus, M R , is one of several material properties and serves as a measure of the Young's modulus, E, when short-duration dynamic loads are applied. For this procedure, triplicate specimens four inches (10.16 cm) in diameter and 2,5 inches (6 0 35 cm.) in height are prepared for each mix design using Marshall compaction methods. The specimens may be tested in the dry condition, after saturation and again after freeze-and-thaw, to assess the effects of conditioning,

The diametral specimen is secured in a sample collar and placed on its side under the loading cell of an MTS machine. Two LVDT transducers are attached to the collar and adjusted until the transducer tips just touch the oppo- site sides of the sample. Elastic deformation across the horizontal diameter of the specimen is measured by the transducers, which are attached to a two channel Brush 250 recorder, which measures transducer output on one channel and the applied load on the other channel. Horizontal movements and effects of vibration are cancelled out by the additive coupling of the transducers.

Dynamic loads (ranging from 20 to 35 lbs (9, 1 to 15.9 kg) in this study) are applied through the load cell, using a haversine function of 8 Hz per second applied every three seconds. This gives a load duration of one second repeated twenty times per minute. The three-second interval between loads allows substantial specimen creep recovery.

The modulus of resilience is calculated from the measured dynamic loads and elastic deformation using the following formula:

P + 0.27341 .1% - IR . 6 t where

M = modulus of resilience P, magnitude of dynamic load Poisson's ratio, which is selected by the researcher (in this study, the ratio was selected at 0.35, which subsequent data verified) specimen thickness 6 = total deformation

A-16 Fracture Toughness

The fracture test for Marshall specimens is a relatively new procedure, developed at the Ohio State University. The specimens, prepared in triplicate for each mix design, are loaded at a known stress rate by applying an increasing ramp loading function until fracture occurs. The maximum load the sample can withstand at the known stress,rate will give an indication of the sample's strength.

The sample is first notched using a concrete.saw to a depth of .75 inch (1.895 cm), with the notch width being about 1.25 inches (3.175 cm)..T'ne.initial crack is then created by sawing.a groove at the•base of the notch: The initial crack length, C, can be selected by the investigator. A crack•length of .10 inch (.254 cm) was used in this investigation. The sample is then placed under the loading cell of the NITS machine and subjected to an increasing ramp loading function at the known stress rate (1000 psi was used in this -investigation) until complete fracture occurs.

The sample's resistance to fracture is defined by K 10 , fracture toughness, a . material constant that is calculated using the following formula (which applies only to diametral specimens): P(0.92 ÷ C.2394C ± 0.5552C 2) Klc t where Klc = fracture toughness • the load at complete sample fracture • initial crack length • specimen thickness (using Marshall specimens four inches (10.16 cm) in diameter and five inches (12.7 cm) in height)

Fatigue Test

This procedure is conducted on asphaltic beam specimens 2 x 2 x 24 inches (5.03 x 5.08 x 60.96 cm) prepared in triplicate for each mix design. The beam is placed on an elastic (gum rubber block) foundation measuring 2 x 2 x 24.5 inches and placed under the loading plate of the NITS machine. The loading plate is lined with a rubber cushion. The dynamic load, selected at 40 to 50 percent of the maximum load obtained through fracture tests, is applied through a haversine loading function of 10 HZ frequency, although only two wave functions are allowed to pass through the loading cell per second (the remaining eight cycles are suppressed). The test is performed in the controlled stress mode, with the load kept constant and monitored through a two-channel Brush 280 recorder. Crack lengths on both sides of the beam are recorded, along with the corresponding number of fatigue cycles, at various intervals during the test until complete fracture occurs, providing information on the variations of crack length with fatigue cycles.

A- 17 RECOMMENDATIONS FOR IMPLEMENTATION AND FURTHER RESEARCH

In years to come, as supplies of conventional aggregates become de- pleted and stockpiles of bottom ashes continue to grow, these "waste" materials may prove a highly valuable resource to the construction industry, However, if widespread utilization of these materials with satisfactory results is to be anticipated, industry and government must work together to encourage potential consumers by furnishing concise guidelines to material use, behavior, quality and supply.

The implementation of this investigation should begin with the revision or modification of existing state highway department specifications to allow the appropriate uses of _dry and wet bottom ashes in asphaltic mixtures. The guidelines for material selection, testing and acceptance, as recommended in this report, could be modified for incorporation in such specifications,

Quality control guidelines for the production and stockpiling of these materials should be formulated to better insure adequate supplies of a depend- able aggregate. Such guidelines might include:

a. Separation of dry, wet and fly ashes prior to stockpiling;

b. Modification of stockpiling methods to insure that fine and coarse fractions of the ash are not badly segregates;

c. Limiting the amounts of pyrites, sulfate sludge and other deleterious materials that are incorporated into the ash stockpile,

However, these and other quality control guidelines can be implemented only if power-generating industries begin to view ashes as a marketable product rather than as waste and are willing- to invest the time-and money in modifying stockpiling procedures to meet such guidelines.

To identify the most promising sources of bottom ashes and to promote greater utilization of these materials, potential suppliers should provide such data as coal source, type and chemical characteristics; coal-burning techniques; ash production rate and stockpiling methods; availability of ash for construction use; and analyses of ash gradation, specific gravity, density and chemical composition. Such data, if made available through a national plant survey conducted by the power-generating industry, would certainly enhance consumer choices and encourage wider use of these materials.

A-18 This research investigation has also documented areas in which further research needs to be done. Of particular importance is the need for further evaluation of bottom ash-asphalt mixtures subjected to saturation and adverse climatic conditions. The data presented has indicated that bottom ash mixtures exhibit a substantial increase in engineering properties due to saturation. This appears to be a unique characteristic of bottom ash mixtures and contradictory to what one normally expects from conventional aggregate mixtures, which tend to lose strength upon saturation. The examination of data indicates that the increase in ash mixture properties is not random or coincidental; rather, it was observed in all experimenta: 'data including modulus of resilience, fracture strength and indirect tensile strength. If there is a validity to this peculiar observation, there could be significantly greater benefits to using bottom ash, particularly in base and subbase courses, where the potential for saturation is greater.

Based upon the criticisms of such quality tests as Los Angeles abrasion and soundness tests, there is a need to develop new testing methods that are specifically geared toward identifying the material and engineering properties of these materials and toward more accurate prediction of their behavior and performance in bituminous mixtures,

As documented by this investigation and others, wet bottom ash is not as versatile a material as dry bottom ash, due to its. uniform size and smooth glassy texture. Surface course and friction wearing courses could be designed using up to 50 percent wet bottom ash and additional research could be done toward optimizing mixtures incorporating this material, But of greater concern to researchers is the high internal stresses built up in wet bottom ashes during the quenching and solidification.process. Further research is needed to identify the mechanism of thermal _fracture and to assess how this property affects the performance of wet bottom ash in soundness testing, freeze and thaw conditions, etc. APPENDIX B

USE OF POWER PLANT BOTTOM ASH IN HIGHWAY PAVEMENT APPLICATIONS

SPECIFICATION/GUIDELINES Found in the Literature

C-1. Kinder [20]

C-2. National Ash Association [31]

C-3. Saskatchewan Highways and Transportation [14]

C-4. State of Illinois [2]

C-5. State of New Jersey [2]

C-6. State Highway Commission of Kansas [2]

C-7. North Dakota State Highway Department

C-8. State of Ohio [2]

C-9. State of West Virginia [2] GUIDELINES/SPECIFICATIONS FROM KINDER, Ref. 20

GUIDELINES FOR MIXING AND PLACING The guidelines developed for cement-treated bottom ash have been derived primarily from field and laboratory experiences. Although the bottom ash from different plants will vary physically and chemically, these guidelines can normally be applied when utilizing cement-treated bottom ash. 1. Materials

A. Water - The water quality assurance is in accordance with standard AASHTO and ASTM procedures for concrete production.

B. Bottom Ash - The bottom ash used in the mix should undergo a complete laboratory analysis to determine chemical and physical characteristics. Of particular interest is the gradation and the strength criteria when mixed with a certain percent cement and moisture. A determination must be made on the moisture content of the bottom ash in stockpile if the material is removed from a lagoon. If the bottom ash is not stockpiled and allowed to drain for 2-3 days, normally compensation for the moisture content would have to be made in the mixing operation. The bottom ash should be free of pyrites and other deleterious materials. C. Cement - The portland cement used in the construction mix is quality assured in accordance with the Department's standard system for control with inter- mediate sampling and testing at the job site.

2. Mixing Operation

Many elements arc involved in assuring a basemix of uniform quality. The predominant factor would be a sufficient amount of testing on the original plant calibration for proper proportions of cement and ash. At the John Amos Plant the calibration was checked once daily by truck weights. In addition, daily calibration checks of the cement usage versus total tons produced provided a reliable cross check. The quantity of water necessary for cement hydration and maximum compaction should be added and mixed in the pug- mil]. A uniform moisture control is largely dependent on an experienced plant operator by visual observation. Quick checks were made by using the speedy moisture test and the nuclear gauge. B-2 Several methods can be used for mixing cement-.treated bottom ash. Two different schemes were considered: a mix-in-place anti a . centrai mix opnNlion. The mix-in-place method cdn -s-i- ts of distributing bottom ash in place over the work area and then spreading cement evenly over the bottom ash. The required amount of moisture is added and then a disc or har- row is used to mix the material in place. This is the simplest method of mixing but is undesirable because of the nonuniformity of the mix. We attempted this method on a coal pile base at the John Amos Plant. Central mixing was the method we chose to make the cement-treated bottom ash used in West Virginia. A pugmill was located adjacent to the bottom ash pond where bottom ash could be readily stocked. Accurate- ly controlled amounts of cement, water and bottom ash were injected into a mixing chamber where they were mixed to the desired composition. This mixture was then hauled to the project site in trucks covered with tarps to minimize evaporation of moisture from the mix. 3. Spreading Prior to spreading the cement-treated bottom ash, the subgrade should be moistened if overly dry. This will prevent the subgrade from pulling the moisture from the base course prior to compacting. The mixture is spread with a jersey box or an asphalt paver in a uniform lift that produces the required compacted thickness. A compacted 6" lift has been used on all secondary roads constructed to date. We have placed some material under very adverse weather conditions; but, ideally, the base - course should never be placed when the temperature is less than 40° F. 4. Compaction Several different types of compaction equipment have been used on the cement-treated bottom ash with. excellent results. Both pneumatic-tire rollers and vibrating rollers have been used successfully. If desired, a piece of tracked equipment can be used to make the first pass across the lift prior to the compaction plants. We used a jersey spreader mounted on a tracked vehicle because of the type of terrain where this base was being used. Normally, six to eight passes were required to obtain desired compaction. A test strip can be utilized to determine the actual number of passes required for a particular compaction plant. 5.. Curing Because most of the paving program is carried out in the hot summer months, a moist cure is used on the cement-treated bottom ash. A water truck is used to spray the surface of the base course at regular intervals during the daylight hours for a 72- . hour period. After the curing process and prior to paving, a tack coat is applied at the rate of 0.15 gallons per square yard. Some surface cracks appeared in the base on very hot days because of the rapid cure, but using the water truck helped to eliminate most of these cracks. 6. Tests A number of tests are made on the base course during the placement of the material. These tests are as follows: 1. Depth of Lift 2. In-Place Density 3. Moisture Content 4. Unconfined Compressive Strength Even though some fluctuation in moisture content was experienced, a good uniformity in dry density was achieved.- WIDENING PROJECTS USING CEMENT-TREATED BOTTOM ASH With the completion of the Interstate System, secondary roads will have to be upgraded to reach the major thoroughfares. Cement- treated bottom ash is being used as the base course for widening projects in several Districts in West Virginia. The mix used in this application is the same as the one used in the base construction program; however, the placement and compaction procedures are different. The following sequence is used in a widening project: 1. Material is trenched along the existing pavement the width to he widened (2-3') by 1' deep. 2 A 6" compacted lift of bottom ash is placed in the cut and compacted, providing a drainage system for the base. 3. A 6" lift of cement-treated bottom ash is placed over the compacted lift. 4 This lift is rolled first with a three-point roller to squeeze the material against the old pavement and then with a smooth-drum vibratory roller to obtain desired compaction. 5 The base is then moisture-cured with a water truck. 6. The material is then sealed with a bituminous tack coat. 7. A 2" hot-laid bituminous concrete leveling course is added to the pavement area, providing a new crown for the pavement section. The entire pavement area is then covered with 1" of bituminous wear surface. SPECIFICATION GUIDELINES FOR CEMENT-FLYASH MIXTURES FROM NATIONAL ASH ASSOCIATION, Ref. 31

A. Materials

1. Fly Ash The fly ash to be used for the construction project should be subjected to the laboratory testing program out- lined in Section IV of this manual and should satisfy the strength criteria described therein when mixed with a certain amount of cement and a certain percentage of moisture necessary to achieve the maximum density of the mix in accordance with ASTM Designation: D 558-57. The moisture content of the fly ash as-received should be determined and compensated for in the mixing operations.

2. Water Water to be used in the construction mix should be clean and free from vegetable matter, acid, oil, alkali, sugar, or other substances harmful to the finished product.

3. Cement Portland cement to be used in the construction mix should be ASTM Type I and should comply with the appropriate state or local highway agency requirements for Portland cement to be used in roadway construction.

4. Construction Mix

The various proportions of the materials comprising the base course construction mix are most conveniently specified in terms of pounds (kg) of fly Ish and cement and glllons (m3 ) of water per cubic foot (m ) or square yard (m ) of compacted mix. The amount of water specified should be equivalent to the optimum moisture content of the fly ash- cement mix plus two percent as determined by ASTM Designa- tion: D 558-57.

B. Subgrade Preparation The subgrade should be shaped to the desired crown and grade and proofrolled to the degree of compaction necessary to produce the subgrade strength used in the design procedure. The subgrade should be moist in order to prevent absorption of moisture from the base course, but not wet. Any unsuitable material; ruts; and soft or wet areas caused by improper drainage, equipment, or any other cause should be removed, and the area backfilled with suitable material and compacted.

C. Mixing A number of mixing methods can be used for cement- stabilized fly ash. Generally, these methods can be classified as central mixing methods and mix-in-place methods.

The first method, central mixing, is usually done with a concrete-type batch mixer or a pugmill mixer and offers a high degree of quality control. A permanent batch plant may be available at the power station or at a concrete central batch plant. Pugmills or small concrete-type batch mixers can also be brought on-site. Accurately controlled amounts of fly ash, cement, and water are introduced into a mixing chamber where they are mixed until a uniform composition is obtained. !latching by weight is generally recommended as opposed to batching by volume. The mixture is then hauled to the construction site in covered trucks to minimize evaporation losses and protect against sudden rainfall. The second method, mix-in-place, involves the distribution of fly ash evenly over the work area, the distribution of cement over the fly ash, and the subsequent addition of moisture and mixing with travelling mixing machines, harrows, or a similar apparatus. While this may be the simplest mixing method, it is the least desirable due to the non- uniformity of the resultant paving mixture and the potential environmental problems of "dusting" by dry cement or fly ash. If this method must be used, the fly ash should be watered adequately prior to spreading to prevent dusting, and additional cement should be added to compensate for any that might be blown away during spreading. Mixing of the base course by the windrow method is not recommended.

D. Spreading If the subgrade is dry at the time of spreading, it should be moistened in order to prevent the absorption of moisture from the base course. The base course should never be spread when the temperature of either the subgrade or the base course is less than 40°F (4°C) At the time of spreading, the moisture content of the base course mix should be two percentage points over optimum to compensate for moisture loss during spreading and compaction operations.

B-7 For all mix-in-place methods, the spreading and mixing operations are combined. When central mixing methods are used for roadway construction, the mixture is spread by means of mechanical spreaders, such as a jersey box or asphaft paver. In the case of parking lot construction, the mix can be tailgated from dump trucks and spread by a dozer. In either case, spreading methods should result in a uniform, uncompacted layer the compacted thickness of which equals the required design thickness. The uncompacted thickness necessary to produce the required design thickness can be determined in a test strip (see Section 1). The compacted thickness of a single layer should not exceed eight inches (204 mm). For cases where the required compacted thickness is in excess of eight inches (204 mm), the base course should be constructed in multiple layers (see Sec- tion H). The value of maximum recommended thickness may vary with the type of spreading and compaction equipment used.

Spreading should progress so that no more th'an 30 minutes elapse between .adjacent passes. A construction joint should be formed along the edge of the previous pass if more than 30 minutes elapse between adjacent passes (see Section _ ‘G). Spreading operations should be terminated during periods of rain.

E. Compaction

No more than 60 minutes should elapse between the start of moist mixing, on-site or off-site, and the start of compaction operations. Ideally, the compaction equipment should follow immediately behind the spreading equipment.

It is recommended that the uncompacted layer receive at least one pass by a piece of "tracked" equipment prior to allowing regular compaction equipment on the base course. In the case of parking lot construction, this will have already been accomplished by the dozer-spreading operation.

The British have obtained their most satisfactory compaction results with pneumatic-tire rollers of the 10-ton (9 Mg) adjustable variety, either self-propelled or towed. Vibrating rollers have been used with only slightly less satisfactory results. The speed of the vibratory roller should not exceed two to three miles per hour, and the rate of vibration should be checked with a vibrometer to achieve optimum efficiency. Roughly four to eight passes are necessary to achieve the desired compaction. The suitability of a particular piece of compaction equipment and the actual number of passes required should be verified on a test strip. The minimum dry density requirement that should be specified for cement-fly ash base course mixes is 100 percent of maximum dry density as determined by ASTM Designation: D 558-57 or AASHO T134. Any uncompacted or partially compacted base mixture which is left undisturbed for more than two hours or is wetted by rain so that the average moisture content is more than two percentage points over optimum should be removed and replaced.

F. Finishing

If necessary, the base course should be fine-graded with a road grader. The surface should then be scarified and proofrolled to insure a finished surface free of ridges, cracks, ruts, and compaction planes.

G. Joints

Straight transverse and longitudinal joints should be formed at the end and edges of each day's construction by cutting back into the completed work to form a true vertical face free of loose or shattered material. All material resulting from the trimming operation should be removed from the area so as not to be mixed into fresh base material. When the bituminous wear surface is constructed for a roadway, it should be placed so that the wear surface joints coincide with the base course longitudinal joints. The engineer may consider the sawcutting of roadway pavement joints at regular intervals in order to control reflective cracking that may occur as a result of shrinkage cracks in the base course.

H. Multiple Layers If the specified compacted thickness of the fly ash- cement base course is greater than eight inches (204 mm), it may be necessary to construct the base course in multiple layers in order to insure proper spreading and/or adequate compaction, with no compacted layer less than four inches (102 mm) in thickness. Each layer should be scarified prior to constructing another layer on top of it. If the upper layer is not constructed the same day as the lower layer, the lower layer should be cured in accordance with Section I until the upper layer is constructed or for a period of up to seven days. Central mixing methods are recommended for multiple layer construction, as mix-in-place methods can produce a thin zone of inadequately stabilized fly ash between the upper and lower layers. . I. Curing

Once the base course has been constructed, it is desirable to construct the bituminous wear surface immediately. If it is not feasible to do this, provisions should be made to protect and cure the base course until the bituminous wear surface is constructed or for a period of up to seven days. Either of two curing materials described below should be applied within 30 minutes of the completion of finishing operations and after the surface of the base course has been . broomed free of all loose and foreign material and/or moistened and rolled to integrate loose and dry surface material:

1. A bituminous curing material, preferably a rapid- curing seal coat such as RS-1, can be applied at the rate of 0.15 to 0.30 gallons per square yard (.0068 to .0136 m 3/m). If necessary, sufficient water to, fill any surface voids in the base course should be applied immediately before the application of the bituminous curing material.

2. A moist cure can be applied in lieu of a bituminous curing material using a water truck or other approved means to spray the surface of the base course with water at regular intervals during the daylight hours to prevent drying of the surface. At no time should the moisture content of the surface of the base course be allowed to fall below the optimum moisture content.

J. Traffic

No traffic should be permitted on the pavement until the bituminous wear surface has been constructed. In addition, if the wear surface is constructed less than a week after base course construction, traffic should not be permitted on the pavement until seven satisfactory curing days have elapsed since the construction of the base course. A satisfactory curing day is any day when the temperature of the completed base does not fall below 50°F (10°C)

K. Test Strips It is recommended that a test strip be constructed prior to actual construction of parking lots or roadways in order to verify compaction criteria and evaluate the adequacy of the compaction equipment to be used on the job. The satisfactory test strip remains in place and becomes a section of the completed roadway or parking lot. Additional test strips should be constructed when there is a change in either compaction equipment or material (type or source).

B-10 The material and equipment used for the test strip should be exactly the same as that being used for the overall project. The method of construction (i.e., mixing, spreading, compacting, etc.) should also be the same. After an initial number of passes by the compaction equipment, and after each pass thereafter, density measurements should be taken to determine the effect of each additional pass of equipment. If the specified compaction requirements cannot be met within roughly eight passes, it would be advisable from an economic standpoint to either increase the pressure (weight) of the equipment being used or change the type of equipment in use rather than continuing to increase the number of pares. A minimum test strip area of 200 square yards (167 m ) is recommended.

L. Tests During construction of the cement-stabilized fly ash base course, a certain number of tests on the base course material are recommended for quality control purposes. The samples for testing should be taken in accordance with good sampling techniques. The tests are as follows:

1. Moisture-Density Relationship (ASTM Designation: D 558-57)

2. Moisture Content

3. Cement Content of Freshly Mixed Base Course Material (ASTM Designation: D 2901-70) 4. In-place Density (ASTM Designation: D 2922-71, Method B)

5. Unconfined Compressive Strength: 7- and 28-day (ASTM Designation: D 1633-63) 6. Depth of Mixing for Mix-in-place Methods (visual). For convenience, Proctor specimens molded in the field at maximum dry density and optimum moisture content can be used for the unconfined compressive strength tests, with the strength results factored for the appropriate 4/d ratio.

M. Construction Cut-Off Dates The general guideline for determining the construction cut-off date for cement-stabilized fly ash base course is that the ambient air temperature should not fall below 50°F (10°C) for a period of seven days following completion of the base course. The pozzolanic reaction in the base material ceases at temperatures below 40°F (4°C), although it will continue once the temperature is increased. If construction takes place early or late in the season, or if unseasonably cold weather occurs during the curing period, the pavement should be protected from freezing by a covering of suitable material, such as hay or straw, and consideration should be given to delaying the opening of the finished pavement to traffic (see Section . J for satisfactory curing day criteria).

In the mid-Atlantic states, the recommended construction period is April 15 through October 15. It is suggested that the engineer refer to the construction specifications of his respective state highway department for construction cut-off dates for lime-pozzolan-aggregate or soil-cement. These dates can be safely applied to cement-stabilized fly ash base courses. SASKATCHEWAN HIGHWAYS AND TRANSPORTATION

SPECIFICATION FOR SUBBASE COURSE (Modification for Lagoon Ash Subbase Material Denoted by (*))

3300-1 DESCRIPTION

The work shall consist of a layer of screened or crushed sand or gravel, with or without binder added, placed on a prepared surface at the locations and in conformity with the lines, grades, and dimensions shown on the plans or designated by the Engineer.

In sections 1, 2, and 3 of this specification, the following definitions will apply:

Subbase aggregate - the aggregate before mixing, when binder is to be added.

- the aggregate before spreading and compacting, when no binder is to be added.

Subbase mix - the subbase aggregate aftermixingwith binder and water but before spreading and compacting.

Subbase course - the subbase aggregate or subbase mix in place on the road during and after spreading and compacting.

3300-2 MATERIALS

Subbase aggregate shall be composed of fragments of durable rock free from undesirable quantities of soft or flaky particles, shale, loam, and organic or other deleterious material.

* Subbase course shall comply with the following requirements:

Type 36 Percent by Weight Passing Sieve Designation U.S. Standard Sieves

3/4 (18 mm) 100 1/2 (12.5 mm) 91 - 100 No. 4 (5 mm ) 70 - 85 No. 10 (2 mm) 45 - 70 No. 20 (900 Wm) 28 - 51 No. 40 (400 um) 20 - 35 No. 100 (160 um) 11 - 21 No. 200 (71 Wm) 8 - 13 Subbase aggregate to be used for lifts of subbase course three (3) inches or greater in thickness, shall be screened over a two (2) inch screen.

Subbase aggregate to be used for lifts of subbase course less than three (3) inches in thickness, shall be screened such that the maximum particle size is not greater than two-thirds (2/3) the depth of the lift.

3300-3 CONSTRUCTION

Overburden shall be removed from material deposits in accordance with the requirements for Removal of Overburden (Specification 2260).

On sections of subgrade where a clay cap is to be removed, the thickness of subbase course will depend upon test results obtained after the clay cap has been removed.

Materials shall: be handled in a manner such that segregation of the coarser and finer factions will not occur.

* Subbase aggregate shall be stockpiled before the screening operation. During this stockpiling operation, the Contractor shall mix the aggregate in order to get a uniform gradation.

* After screening operation begins, the Contractor shall alWays have sufficient subbase aggregate in stockpile for at least twenty-four (24) hours of screening, until the subbase operation is complete.

Subbase aggregate or mix shall be hauled in accordance with the requirements for Haul (Specification 2405).

Failures in the subgrade or subbase course, which develop on a section of road upon which subbase aggregate or mix has been deposited, shall be repaired at no direct expense to the Depart- ment.

* Subbase aggregate or mix shall be spread by motor graders or by other equipment approved by the Engineer. If in the opinion of the Engineer, additional blading is required to ensure a uniform mixture on the road, the additional blading involved will not be paid for directly but will be considered a subsidiary obligation of the Contractor under the contract unit price for subbase course (Item 306). 3300-3 CONSTRUCTION (Continued)

* If excess moisture exists in the subbase course it shall be dried to a moisture content below 18% as determined by Test 9200, at no expense to the Department.

If pneumatic tire rollers are used for compacting, the lift of subbase course shall not exceed four-tenths (4/10) of one foot in depth. If mechanical vibratory rollers are used, the depth of lift may be increased provided that adequate compaction can be obtained.

Subbase courses shall be compacted until no further settlement is apparent and the particules are well keyed into place. If the natural moisture content of the subbase course is insuf- ficient for proper compacting, water shall be added at the road as directed by the Engineer. Water shall be added in a manner such that the underlying material is not adversely affected.

If the subbase course proves to be unstable, the Department will elect to stabilize the subbase aggregate by one of, or a combination of the following methods:

(a) By the addition of binder or filler at the screening plant.

(i) If the Department elects to stabilize any lift of subbase course by this method, Bid Item 322 (Hauling Binder, Filler and Blender Sand) shall apply.

(ii) If, in the opinion of the Engineer, additional blading is required to ensure a uniform mixture on the road, the additional blading involved will not be paid for directly but will be considered a subsidiary obligation of the Contractor under the Contract Unit Price for subbase course.

(b) (i) By addition of emulsion to the compaction water in proportions of approximately one part S.S. 1 emulsified asphalt to nine (9) parts water.

(ii) The Department will supply the S.S. 1 emulsified asphalt.

(c) If the subbase course is still deemed unstable after the addition of the emulsion, soil binder shall be added by itself or as a supplement to the emulsion treated compaction water.

3-15 3300-3 CONSTRUCTION (continued) The final lift of subbase course shall have sufficient stability such that, when compacted, it will not rut or break through during the hauling and placing of the bottom lift of base course.

If binder is used to stablize subbase aggregate, the binder shall be added in a manner such that it is uniformly distributed throughout the aggregate.

When the bottom lift of base course is placed, the subbase course shall be true to grade and cross section and shall be compacted as specified.

The length of windrowed subbase or subbase laid but not covered by base course shall not exceed two (2) miles.

If work must be carried over from one construction season to the next, the following shall apply at the time seasonal operations cease:

(1) There stfall be no subbase aggregate or mix remaining on the road.

(2) There shall be no subbase course not covered by a lift of base course.

(3) If the Contractor fails to comply with (1) and (2) of this paragraph, he shall be responsible for the repair of any failures, which occur on the section, is the subgrade or subbase course.

3300-4 MEASUREMENT

Subbase course will be measured in tons.

If the Contractor elects to stabilize any lift of subbase course using the road-mix method, the subbase course quantity will be the weight of the subbase aggregate only. The hauling of binder or filler from its source to the road will not be measured or paid for.

If the Contractor stabilizes any lift of subbase course by the addition of binder or filler at the screening plant or pit, the subbase course quantity will be the subbase mix weight.

B-16 3300-5 PAYMENT

Payment for SUBBASE COURSE will be at the contract unit price per ton. The unit price will be full compensation for removing overburden; excavating, blending, stockpiling, screening, crushing, loading, dumping, and stabilizing the aggregate; and spreading, shaping, and compacting the subbase course.

Payment for HAULING SUBBASE COURSE will be at the contract unit price per ton mile in accordance with the requirements for Haul (Specification 2405).

Payment for SUBBASE COURSE IN PLACE will be at the contract unit price per ton. The unit price will be full compensation for removing overburden and excavating, blending, stockpiling, screening, crushing, loading, hauling, dumping, spreading, stabilizing, shaping, and compacting the subbase course.

Payment for watering on the road will be in accordance with the requirements for Watering (Specification 2500). The unit price will be full compensation for all work associated with the addition of emulsified asphalt to the compaction water as

specified in Specification 3300 - 3(b)(1).

No direct payment will be made for hauling binder, filler or blender sand if added to the subbase course on the road.

Payment for hauling binder and filler sand to the pit or screening plant will be in accordance with the requirements for Haul (Specification 2405). STATE OF ILLINOIS DIVISION OF HIGHWAYS

STANDARD SPECIFICATIONS FOR ROAD AND BRIDGE CONSTRUCTION Adopted January 2, 1971

Section 703. Fine Aggregates

703.01 Materials: The aggregate materials shall conform to the following' requirements:

(a) Description: The natural and manufactured materials used as fine aggregate shall be defined as follows:

Wet Bottom Boiler Slag. Wet bottom boiler slag shall be the hard angular by-product of the combustion of coal in wet bottom boilers.

Slag Sand: Slag sand shall be the graded product resulting from the screening of air cooled blast furnace slag. Air cooled blast furnace slag shall be the nonmetallic product, consisting essentially of silicates and alumino-silicates of lime and other bases, which is developed in a molten condition simultaneously with iron in a blast furnace. It shall be air cooled.

(c) Gradation: The fine aggregate shall be uniformly graded from course to fine, and when tested by means of laboratory sieves (square openings), shall conform to the designated gradation.

703.03 Fine Aggregate for Bituminous Mixtures: The aggregate shall conform to the requirements of Article 703.01 and the following specific requirements:

(a) Description: The fine aggregate for bituminous mixtures and top dressing of bituminous surfaces shall consist of sand, stone sand, stone screenings, chats, wet bottom boiler slag, or air cooled blast furnace slag.

(b) Quality: The fine aggregate for bituminous mixtures Class I shall be Class B quality or better. . Section 7 04. Coarse Aggregate

704. 01 Materials: The aggregate materials shall conform to the following requirements: •

(a) Description: The natural and manufactured materials used as coarse aggregate shall be defined as follows:

Wet Bottom Boiler Slag: Wet bottom boiler slag shall be the hard angular by-product of the combustion of coal in wet bottom boilers.

Crushed Slag: Crushed slag shall be the graded product resulting from the processing of air cooled blast furnace slag. Air cooled blast furnace slag shall be the nonmetallic product, consisting essentially of silicates and alumino-silicates of lime and other bases, which is developed in a molten condition simultaneously with iron in a blast furnace. It shall be air cooled and shall have a compact weight (ASTM C 29) of not less than 7 0 pounds per cubic foot

704.03 Coarse Aggregate for Bituminous Courses: The aggregate shall conform to the requirements of Article 704.01 and the following specific requirements:

(a) Description: The coarse aggregate shall be crushed gravel, crushed stone, crushed slag or chats. Gravel may be used in lieu of the above for Class A and B bituminous courses.

(b) Quality: For Class A and B bituminous courses, the coarse aggregate shall be Class C quality or better. For Class 1 bituminous courses, the coarse aggregate shall be Class B quality or better. STATE OF NEW JERSEY

8.5.4 Aggregate, Coarse

Coarse aggregate shall be broken stone, washed gravel, blast furnace slag, and boiler slag (for cover material), conforming to the requirements therefore as hereinafter specified and shall be graded as shown in Table A-1. The particular types of coarse aggregate, and the kinds of each type, for various uses shall be specified for each type of construction.

Only one type of coarse aggregate from a specific source, and only one kind of that type, shall be used in any one project unless otherwise approved by the Engineer.

8. 5. 8 Slagt_ Boiler

Boiler slag shall conform to the requirements of Article 8.5.3 and 8.5.4, and to the following requirements:

Boiler slag shall be the fused water-cooled residue from the combustion of pulverized or powdered coal used in electric generating plants, the color of which shall be nearly black.

It shall weigh not less than 85 pounds per cubic foot (1362 kgui per cubic m. ), loose measure as determined by the "Method of Test for Unit Weight of Coarse Aggregate (Dry Loose Measure)" specified in Article 9.1.2.

It shall have a specific gravity of not less than 2.80, a maximum absorption of 1.2 percent in cold water, and shall conform to the grading requirements specified for standard size number 10 in Table A-1. TABLE A-1 STANDARD SIZES OF COARSE AGGREGATES

Nominal size Amounts finer than each laboratory sieve (square openings), percentage by wei•ht Size square 4" 3.5" 3" 2.5" 2" 1.5" 1" 3/4" 1/2" 3/8" #4 #8 #16 #50 #100 Nbr. oienin:s* 1 3.5-1.5 100 90-100 --- 25-60 --- 0-15 ---- 0-5 ------2 2.5-1.5 --- 100 90-100 35-70 0-15 ---- 0-5 ------24 2.5-.75 --- 100 90-100 --- 25-60 ---- 0-10 0-5 ------3 2 - 1 --- 100 90-100 35-70 0-15 --- 0-5 ------357 2 - #4 ___ 100 95-100 --- 35-70 ---- 10-30 --- 0-5 ------4 1.5-.75 ------100 90-100 20-55 0-15 ---- 0-5 ------467 1.5-#4 ------100 95-100 --- 35-70 ---- 10-30 0-5 ------5 1- .5 ______100 90-100 20-55 0-10 0-5 ------56 1-3/8 ------100 90-100 40-75 15-35 0-15 0-5 ------57 1-#4 --- ___' --- 100 95-100 --- 25-60 ---- 0-10 0-5 ------6 .75-.50 ------100 90-100 20-55 0-15 0-5 ------67 .75-#4 ------100 90-100 --- 20-55 0-10 0-5 ---- 68 .75-#8 ___ ------100 90-100 --- 30-65 5-25 0-10 0-5 ---- 7 .50-#4 ______------100 90-100 40-70 0-15 0-5 ---- 78 .50-#8 ------100 90-100 40-75 5-25 0-10 0-5 ---- 8 3/8-#8 ------100 85-100 10-30 0-10 0-5 --- 89 3/8-#16 ------100 90-100 20-55 5-30 0-10 0-5 ---- 9 #4-#16 ------100 85-100 10-40 0-10 0-5 ---- 10 #4-#0** ------100 85-100 ------10-30

* In inches, except where indicated. Numbered sieves are those of U.S. standard sieve series. ** Screenings Note: in. x 25.4 = mm

B-21 STATE HIGHWAY COMMISSION OF KANSAS

SPECIAL PROVISIONS TO THE STANDARD SPECIFICATIONS EDITION OF 1966 Adopted 10-2-70

1.0 Description

This special provision covers the requirements of aggregates for asphaltic concrete ( Type HM-Special).

2.0 Individual Materials

(a) Coarse Aggregate: The coarse aggregate shall be a boiler slag (ceramic aggregate) produced by burning coal in wet bottom boilers. The slag shall be a hard, glass-like material meeting the approval of the Engineer. Prior to its incorporation into the final mix, the boiler slag shall meet the following requirements:

Sieve Size Percent Retained Number 4 0-3 Number 8 9-18 Number 16 50-60 Number 30 78-88 Number 50 89-96 Number 100 93-100 Number 200 94-100

(b) Fine Aggregate: Fine aggregate shall be a natural sand meeting the following requirements:

Sieve Size Percent Retained Number 16 0 Number 30 0-3 Number 50 28-36 Number 100 76-82 Number 200 93-100

Plasticity Index, not more than 5

(c) Mineral Filler: Mineral filler shall be a finely ground limestone meeting the following requirements: Sieve Size Percent Retained Number 50 0-2 Number 100 0-4 Number 200 0-15

(d) Point of Acceptance: Acceptance tests for each individual aggregate will normally be conducted on samples obtained from a single location to be determined by the Engineer. Other tests will be conducted for information only. The Commission reserves the right to re-sample, re-test and, if necessary, reject any material subsequent to acceptance testing if there is any evidence that the characteristics of the material have been adversely changed by improper handling.

3. 0 Asphalt

Asphalt used for this work shall be AC-3 grade.

4. 0 Combined Materials

The proportions set forth below shall be established at the cold feeds for the various aggregates. The proportions shall be based on the dry weight of the final mix. The mineral filler shall not be fed through the drier.

Coarse Aggregate (Boiler Slag), percent 64 (± 2) Fine Aggregate (Fine Sand), percent 32 (.4- 2) Mineral Filler (Ground Limestone), percent 4 (± 1)

The exact proportions shall be as directed by the Engineer.

The moisture in the final mixture shall not exceed 0.35 percent.

5. 0 Methods of Test

Tests to determine compliance with this special provision shall be conducted in accordance with applicable provisions of Part Y of the Standard Specifications. NORTH DAKOTA STATE HIGHWAY. DEPARTMENT 810-5 MINERAL FILLER

810-5.1 General Requirements

Mineral filler shall be approved by the Engineer, shall be non- plastic, and shall consist of limestone dust, portland cement, hydrated lime, crushed rock screenings, or fly ash.

810-5.2 Gradation

Not less than 98 percent of the mineral filler shall pass a Num- ber 30 sieve, not less than 85 percent shall pass a Number 100 sieve, and not less than 65 percent shall pass a Number 200 sieve.

810-5.2.1 For the purpose of these specifications, fly ash is defined as the finely divided residue that results from the combustion of lignite and is transported from the boiler by flue gases and shall conform to the following:

Moisture content, maximum percent 3.0 Loss on ignition, maximum percent 6.0

STATE OF OHIO DEPARTMENT OF HIGHWAYS

SUPPLEMENTAL SPECIFICATION 835: Aggregate Lime-Fly Ash Base January 10, 1969

835.01 Description

This item shall consist of a mixture of aggregate, hydrated lime and fly ash mixed, placed and compacted in accordance with the requirements hereinafter set forth and in conformity with the lines, grades and cross sections shown on the plans.

This construction may involve patents and if so, the provisions of 107.03, Patented Devices, Materials and Processes of the Construction and Material Specifications of the Ohio Department of Highways shall govern.

835. 02 Materials

(a) Hydrated lime shall meet the requirements prescribed in standard specifications for Hydrated Lime for Masonry, ASTM C 207.49, Type N for chemical composition, residue, sampling, inspections and methods of test (Sections 3-b, 4 and 5 are not relevant to the intended usage).

(b) Fly ash shall meet the requirements of ASTM C 593-66T, with the exception of Section 7 for plastic mixes.

(c) Aggregate for this course shall be sound and durable limestone, slag or gravel which shall meet the following grading requirements:

Sieve Size Total Percent Passing 2 inches 100 1 inch 70-100 3/4 inch 60-100 3/8 inch 45-85 Number 4 35-75 Number 40 8-35 Number 200 0-15

The fraction of these materials passing a Number 40 sieve shall have a liquid limit of not greater than 30 and a plasticity index not greater than 6.

When tested for soundness in accordance with Method of Test for Soundness of Aggregates by use of Sodium Sulfate, AASHO Designation T-104, the weighted loss of the aggregate shall not exceed 25 percent except in case of an aggregate where the major portion of the unsound materials acquires a mudlike condition during the test, the soundness shall exceed 15 percent.

835.03 Composition

The hydrated lime, fly ash and aggregate shall be combined in such proportions that the composition of the resulting mixture will produce the de sired density and stability. Samples of the materials proposed for use shall be submitted to the Laboratory at least 90 days before the planned construction of this item, for evaluation, approval and proportioning.

STATE OF OHIO DEPARTMENT OF HIGHWAYS

SUPPLEMENTAL SPECIFICATION 918: Steam Boiler Slag Asphalt Mix August 5, 1965

918.01 Description

This mix shall consist of wet bottom steam boiler slag, sand and asphalt cement for a surface course or deslicking. It shall be capable of application by means of bituminous concrete pavers or spinner spreaders.

918.02 Materials

Asphalt Cement Specification 702.01 (70-85 or 85-100) Steam Boiler Slag Specification 901 Sand Specification 703.05

918.03 Composition

Slag, sand and asphalt cement shall be combined in such proportions that the composition by weight of the finished mixture shall be as directed by the Engineer with the aggregate and asphalt within the following limits:

Aggregate, minimum of 40 percent slag and maximum of 60 percent sand 92 - 95 percent

Asphalt Cement 5 - 8 percent

918. 04 Mixing

Plant equipment shall conform to 401. 04. The bitumen content of the mix shall be maintained within the tolerance in 401.02. The proportions , of slag and sand shall not vary from the job mix more than + five percent.

STATE OF OHIO DEPARTMENT OF HIGHWAYS

SUPPLEMENTAL SPECIFICATION 901: Steam Boiler Slag May 18, 1965

901. 01 Description

Steam boiler slag shall be the residual of combustion of coal in high pressure steam boilers, and it shall consist of sound, durable, angular, un- coated pieces free from soft friable particles, clay and organic material.

901. 02 Grading

Sieve Size Total Percent Passing 1/2 inch 100 Number 4 90-100 NuMber 8 55-95 Number 16 15-50 Number 30 1-20 Number 50 0-10

901. 03 Fineness Modulus

Aggregate from any one source having a variation in fineness modulus greater than ± 0.20 from the fineness modulus of the representative sample may be rejected.

901.04 Soundness

Sodium sulfate soundness loss shall not exceed five percent. STATE OF WEST VIRGINIA DEPARTMENT OF HIGHWAYS

STANDARD SPECIFICATIONS, ROADS AND BRIDGES Adopted 1972

Section 702. Fine Aggregate

702.3 Fine Aggregate for Asphaltic Mixtures: Fine aggregate for asphaltic mixtures shall meet the requirements of ASTM Designation D 1073, except that the gradation requirements shall be waived.

703.3 Slag: Slag shall be air cooled blast furnace slag, reasonably uniform in density and quality, and free from dirt and other objectionable matter. When tested in accordance with ASTM Designation C-29 and when standard sizes are combined in the proportions used in the job mix formula, the slag shall weigh not less than 70 pounds per cubic foot (1121 kgm/m 3 ) when used in portland cement concrete or hot-laid bituminous concrete surface courses, and not less than 60 pounds per cubic foot (961 kgm/m 3 ) when used in other applications.

Slag shall also meet the requirements of Articles 703.1.2, 703.1.3 and 703.1.4.

In addition to air cooled blast furnace slag, other slags having demonstrated a satisfactory service record, or which meet the applicable physical requirements for blast furnace slag, may be used with the approval of the Engi- neer. Electrometallurgical slag and wet bottom boiler slag may not be used as a portland cement concrete aggregate. When electrometallurgical slag is used as an aggregate in bituminous construction and payment is on a tonnage basis, proper allowance will be made for the difference in weight per cubic foot (per cubic meter).