Three 750-foot test sections of a 22-foot wide roadway were constructed on newly constructed subgrade in May and June, 1988. The three experimental sections contained experimental base and subbase layers comprised of mixtures utilizing by-product materials from a coal-fired power plant One test section included a base layer containing residue from an atmospheric fluidized bed combustion (AFBC) process, size No. 57 aggregate, and Class F fly ash. The second test section included a base layer constructed ponded fly ash, hydrated lime, and dense-graded aggregate. The third test section included a subbase layer constructed of pond ash stabilized with AFBC residue. A control section was included in the study for comparison purposes. Previous reports have documented preliminary engineering, construction details, and initial performance evaluations of the three experimental sections constructed on State Route 3074 in McCracken County, Kentucky. This report summarizes performance information derived from the field trials. Performance measurements included distress surveys, Road Rater deflections, pavement rutting measurements, and field cores of the experimental base and subbase layers were obtained for laboratory evaluations.

The two test sections containing residue from the AFBC process were regarded as failures due to the excessive expansion of the materials, although efforts were made to eliminate, or minimize, the inherent expansive properties of the residue by prehydrating the AFBC residue prior to its use in the mixtures. The two layers were eventually removed and replaced with conventional materials. The remaining experimental section has given good performance and service. No significant distresses have been noted. Rutting measurements indicated less rutting occurring in the ponded fly ash-hydrated lime-dense grade aggregate section than in the control section. Analyses of deflection data indicate superior structural characteristics compared to the control section. Unconfined compression tests indicate excellent strengths of the experimental mixture. The accomplishment of this application confirms that waste fly ash may be used successfully in stabilized road base construction.

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The contents of this report reflect the views of the authors, who are responsible for the facts and accuracy of the data presented herein. The contents do not necessarily reflect the official views or policies of the University of Kentucky, the Kentucky Transportation Cabinet, or the Federal Highway Administration. This report does not constitute a standard, specification, or regulation. The inclusion of manufacturer names or trade names are for identification purposes and are not to be considered as endorsements.