Evaluation of the Use of Coal Combustion B-products in Highway and Airfield Pavement Construction

282 Pages·2008·10.13 MB·English

Technical Report Documentation Page
1. Report Number 2. Government Accession No. 3. Recipient's Catalog No.
TX-971 2969-1 F
4. Title and Subtitle 5. Report Date
EV ALUA TION OF THE USE OF COAL COMBUSTION BY-PRODUCTS November 1996
IN HIGHWAY AND AIRFIELD PAVEMENT CONSTRUCTION 6. Performing Organization Code
7, Author(s) 8. Performing Organization Report No.
Donald Saylak, Cindy K. Estakhri, Rajan Viswanathan, Dustin Tauferner, and Research Report 2969-1 F
Harsha Chimakurthy
9. Perfonning Organization Name and Address lO, Work Unit No.
Texas Transportation Institute
The Texas A&M University System 11. Contract or Grant No.
College Station, Texas 77843-3135 Study No. 7-2969
12. Sponsoring Agency Name and Address 13. Type of Report and Period Covered
Texas Department of Transportation Final:
Research and Technology Transfer Office September 1995 -August 1996
P. O. Box 5080 14. Sponsoring Agency Code
Austin, Texas 78763-5080
15. Supplementary Notes
Research performed in cooperation with the Texas Department of Transportation.
Research Study Title: Evaluate the Use of Coal Combustion By-Products in Highway and Airport Pavement
Construction
16. Abstract
The objective of this study was to exploit the beneficiation and utilization of coal combustion by-products (CCBPs) as
low-cost alternate aggregates and stabilizers in roadway and airfield construction. A literature review and laboratory
investigation were performed to investigate the use ofCCBPs in three highway construction applications: (I) fly ash
for subgrade stabilization, (2) flue gas desulfurized (FGD) gypsum and Gypsite for base and subbase construction
materials, and (3) bottom ash (with sulfur modification) in asphaltic concrete mixtures.
Results from field trials utilizing CCBPs in roadbases indicate good to excellent performance characteristics and
negligible environmental impact. Class C and lime-enhanced Class F fly ashes were shown to be effective stabilizers
for both clayey and sandy soils. The field trials showed that sulfate-resistant cements and Class C fly ashes provide a
wide range of strengths in stabilized sulfate and sulfite roadbases.
The use of sulfur improved the crushing strength and reduced the asphalt demand associated with bottom ash in
asphaltic concrete mixtures. Sulfur modification required asphalt contents equal to and often less than for mixtures
using conventional aggregates.
Based on its availability, lower cost, safe use, and demonstrated performance, CCBP materials should find increasing
use especially in those regions of Texas experiencing dwindling or non-existant aggregate sources.
17. Key Words 18. Distribution Statement
Coal Combustion By-Products, Coal Ash, Fly Ash, No restrictions. This document is available to the public
Bottom Ash, FGD Gypsum, Sulfur, Highway through NTIS; National Technical Information Service
Construction 5285 Port Royal Road
Springfield, Virginia 22161.
19. Security Classif.(of this report) 20. Security Classif.(of this page) 21. No. of Pages 22. Price
Unclassified Unclassified 284
Fonn DOT F 1700.7 (8-72) Reproduction of completed page authorized

EVALUATION OF THE USE OF COAL COMBUSTION BY-PRODUCTS
IN mGHWA Y AND AIRFIELD PAV EMENT CONSTRUCTION
by
Donald Saylak
Research Engineer
Texas Transportation Institute
Cindy K. Estak:hri
Assistant Research Engineer
Texas Transportation Institute
Rajan Viswanathan
Graduate Research Assistant
Texas Transportation Institute
Dustin Tauferner
Graduate Research Assistant
Texas Transportation Institute
and
Harsha Chimakurthy
Graduate Research Assistant
Texas Transportation Institute
Research Report 2969-1F
Research Study Number 7-2969
Research Study Title:
Evaluate the Use of Coal Combustion By-Products
in Highway and Airport Pavement Construction
Sponsored by the
Texas Depmnnent of Transportation
November 1996
TEXAS TRANSPORTATION INSTITUTE
The Texas A&M University System
College Station, Texas 77843-3135

IMPLEMENTATION RECOMMENDATIONS
The following are recommendations for implementing the use of coal combustion by
products in highway and airfield pavement construction:
1. This project was proposed as Phase I of a two-phase study. It is recommended that Phase
II (a field testing research program) be implemented at this time. It is recommended that a
research project (either in-house or university-based) be established to design, monitor
construction and performance of field test sections incorporating coal combustion by
products into highway and airfield pavement construction as discussed in this report. It is
anticipated that all test sections could be constructed in one year. Performance monitoring
should be continued for a minimum of two years.
2. It is recommended that TxDOT construct the following test sections to evaluate the
constructability and performance of coal combustion by-products in highway/airfield
construction:
CCBPs as Subgrade Stabilizers
A-3 Soil:
Test Section 1. 15% Class 'c' fly ash
Test Section 2. 20% Class 'C' fly ash
Test Section 3. 3% Quicklime and 8% Class 'F' fly ash
A-7-6Soil:
Test Section l. Control-4% Quicklime.
Test Section 2. 2% Quicklime and 5% Class 'F' fly ash
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Test Section 3. 10% Class 'C' fly ash.
Test Section 4. 15% Class 'C' fly ash.
CCBPs as Road Base Materials
Test Section 1. Cement Stabilized or HVFA Cement Stabilized FGD.
Test Section 2. Fly Ash (Class 'C') Stabilized FGD.
Sulfur-Modified Bottom Ash (SMBA) Asphaltic Mixtures
Researchers believe that 5MBA asphaltic mixtures have potential for use on general aviation
runways and that this would be an excellent field test; however, it is recommended that an
even smaller scale field experiment be developed first. It is recommended that a field
experiment (100 meters in length) be placed at a location such as Texas A&M's Riverside
Campus. The aggregate fraction of this mixture could be either 100010 bottom ash or 50%
bottom ash as determined by the Project Director. Any of the mixture designs presented in
Section IV would be a good starting point for development of a field trial.
3. Preliminary specifications are presented in Section V of this report. These should be
evaluated and modified as needed during the field testing portion of a Phase II research
program.
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DISCLAIMER
The contents of this report reflect the views of the authors, who are responsible for the
facts and the accuracy of the data presented herein. The contents do not necessarily reflect the
official view or policies of the Texas Department of Transportation (TxDOT) or the Federal
Highway Administration (FHWA ). This report does not constitute a standard, specification, or
regulation, nor is it intended for construction, bidding, or permit purposes.
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TABLE OF CONTENTS
Page
UST OF FIGURES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xv
LIST OF TABLES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxii
SUMMARY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. xxv
SECTION I - INTRODUCTION. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 1-1
BACKGROUND. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 1-1
Coal Combustion By-Product (CCBP) Production ... . . . . . . . . . . . . . . . . .. 1-1
Legislative Developments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 14
CCBP MATERIALS ............................................ 1-7
Fly Ash, Bottom Ash, and Boiler Slag ............................ 1-7
Flue Gas Desulfurized Sulfates (Gypsum) and SuIfites (Gypsites) ........... 1-8
Elemental Sulfur ............................. ~ . . . . . . . . . . .. 1-9
Hydrated Fly Ash . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-10
RESEARCH PROGRAM ......................................... 1-10
Objectives .............................................. 1-11
Materials ............................................... 1-12
Report Organization .............. . . . . . . . . . . . . . ~ . . . . . . . . . . . . 1-12
REFERENCES - SECTION I ....................................... 1-15
SECTION IT - THE USE OF FLY ASH FOR SOIL STA BILIZAT ION . . . . . . . . . . .. 2-1
BACKGROUND . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 2-1
lITERATURE REVIEW ......................................... 2-2
Fly Ash .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 2-2
Soils .................................................. 2-3
Fly Ash and Lime-Fly Ash Stabilization ........................... 24
ix
TABLE OF CONTENTS (Continued)
Page
MATERIALS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 2-6
Soils .................................................. 2-6
Fly Ash . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-11
Lime . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-11
TEST DESCRIPTIONS .......................................... 2-14
MOISTURE-DENSITY RELATIONSHIP FOR A-3 SOIL .................... 2-17
UNCONFINED COMPRESSIVE STRENGTH FOR A-3 SOIL ................. 2-21
AITERBERG LIMITS FOR A-7-6 SOIL ............................... 2-24
MOISTURE-DENSITY RELATIONSHIP FOR A-7-6 SOIL ................... 2-24
UNCONFINED COMPRESSIVE STRENGTH FOR A-7-6 SOIL ............... 2-24
ONE-DIMENSIONAL EXPANSION FOR A-7-6 SOIL ...................... 2-27
SUMMARY OF FINDINGS AND RECOMMENDATIONS . . . . . . ............. 2-27
n ......................................
REFERENCES - SECTION 2-31
m -
SECTION USE OF BY-PRODUCT GYPSUM IN ROADWAY
CONSTRUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 3-1
BACKGROUND . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 3-1
By-Product Gypsum ........ . . . . . . . . . . . . . . . . . . . ~ . . . . . . . . . . .. 3-1
Coal Combustion By-products (CCBP) ............................ 3-2
Dry Bottom Ash and Boiler Slag ... . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 3-2
Flue-Gas Desulfurization Gypsum ............................... 3-2
Tn EXPERIENCE WITH BY- PRODUCT GYPSUM . . . . . . . . . . . . . . . . . . . . . .. 3-5
Fly Ash and Cement-Stabilized Gypsum ........................... 3-5
Problems Areas with By-Product Gypsum Construction ................. 3-11
Problems Areas with Gypsum Roadbase Construction .................. 3-11
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