Pavements

Materials Notebook

Chapter 6 - Stabilization

May 1997

1. Technical Advisory on Use of Coal Ash and Embankments May 2, 1988 Memorandum 6-1
2. Use of Coal Ash In Embankments and Bases May 16, 1988 Technical Advisory T 5080.9 6-2 Regulatory Background on the Use of Coal Ash Products in Highway Construction 6-12
3. List of Standard Stabilization Specifications and Tests 6-14

U.S. Department of Transportation Federal Highway Administration

MEMORANDUM

Attached for your use is an advance copy of the subject Technical Advisory (TA). The official distribution will occur in approximately 6 weeks.

The purpose of the TA is to give guidance on two high volume uses of coal ash. There has been interest generated in this area by the passing of the Surface Transportation and Uniform Relocation Assistance Act of 1987 which provided for an incentive for the use of coal ash (See FHWA Notice 5080.109).

In particular, please note paragraphs 3a(2) and 4a which point to the need for considering the use of this material as an experimental feature.

In addition, an attachment entitled "Regulatory Background on the Use of Coal Ash Products in Highway Construction" is included. This document should be sent to the division offices since it will not be included in the official distribution of the TA.

Any questions concerning this subject should be directed to the Materials Team at 366-1571.

SIGNED WILLIAM A WESEMAN
William A. Weseman

2 Attachments

Use of Coal Ash in Bases and Embankments - FHWA Technical Advisory T 5080.9

May 16, 1988

Regulatory Background on the Use of Coal Ash Products in Highway Construction

1. The Resource Conservation and Recovery Act (RCRA) of 1976 authorized the Environmental Protection Agency (EPA) to issue guidelines for the use of recycled materials. These guidelines were to be used by Federal agencies in procuring materials. The RCRA also contained a provision that allowed any party to file a civil suit against any other party including the U.S. Government or any individual if the party was not procuring material in-accordance with a specific guideline.
1. The first guideline issued concerned the use of fly ash in Portland cement concrete. The guideline was issued on January 28, 1983, with an implementation date of one year after publication. The guideline called for the elimination of discriminatory language from the specifications of procuring agencies for the use of fly ash in concrete
2. The Federal Highway Administration (FHWA) believed that the guideline did not apply to the Federal-aid program since the program does not directly procure material. After considerable discussion, Congress settled the issue in a conference report on the amendments to the RCRA. On January 4, 1985, the FHWA issued a memorandum indicating that the guideline did apply to the Federal-aid program and gave the States 1 year to remove discriminatory language from their specifications.
3. The RCRA was amended in 1984. The amendments indicated that a procuring agency must procure items with the highest percentages practicable of any recycled material that was the subject of a guideline. Exceptions are allowed for economic considerations and performance. This was a change from the previous guideline which only required the opportunity for the material to be used. Congress also directed the EPA to issue four new guidelines. The subject of two of the guidelines was directed by Congress and concerned recycled paper and tires while the subject of the other two guidelines was left up to the EPA.
2. In December 1984, the Utility Solid Waste Activities Group (USWAG) petitioned the EPA to issue a guideline on all uses of coal ash. Due to difficulty in resolving EPA's environmental concerns in using fly ash in embankments and the technical problems associated with determining the quality of bottom ash, these two items were eliminated from a September 1985 petition by USWAG to the EPA.
1. On March 24, 1986, the FHWA responded to the EPA indicating that the FHWA had no objections to the issuance of a guideline for the use of fly ash as a mineral filler in asphalt pavements, soil stabilization, and pavement undersealing. In the case of lime fly ash aggregate bases, the FHWA objected to the issuance of a guideline because of concerns over the lack of nationally verified pavement design criteria and mix design criteria along with concerns over cracking of the bases.
2. The FHWA's objections were centered on the issuance of a guideline and not on the material itself. The criteria for the EPA to issue guidelines indicates that the use must be technically proven and economically feasible. Since there was not then and still is no nationally verified pavement and mix design criteria for lime fly ash aggregate bases, the FHWA considered it to be inappropriate to issue a guideline on this subject. However, it is appropriate to use the material in those States which have experience with the material or by other States to gain field experience and performance with the material

List of Standard Stabilization Specifications or Tests

• AASHTO T-134 Moisture-Density Relations of Soil-Cement Mixtures
• AASHTO T-135 Wetting-and-Drying Test of Compacted Soil-Cement Mixtures
• AASHTO T-136 Freezing-and-Thawing Tests of Compacted Soil-Cement Mixtures
• AASHTO T-144 Cement Content of Soil-Cement Mixtures
• AASHTO T-211 Determination of Cement Content in Cement Treated Aggregate by the Method of Titration
• AASHTO T-220 Determination of the Strength of Soil-Lime Mixtures
• AASHTO T-232 Determination of Lime Content in Lime-Treated Soils by Titration