This report presented a study of the application of self cementing fly ash stabilized cold in-place recycled material to the base course of pavement for County Trunk Highway "JK" in Waukesha County, Wisconsin. The new pavement structure consists of a 150mm HMA layer over a 305mm fly ash stabilized CIR base course. Eight percent of fly ash by weight was applied and moisture was controlled at the optimum water content of five percent for maximum strength. FWD tests were conducted four days after construction. The non-linear finite element program, MICHBACK, was used to backcalculate the properties, especially moduli, of the pavement layers. The structural number as well as the structural coefficient of each layer of pavement was obtained, based upon the FWD test data. It was found that fly ash stabilized CIR material has a modulus of 1.24MPa. The structural coefficient of fly ash stabilized CIR base course is approximately 0.16 when compared to 0.14 for traditional crushed aggregate base course (CABC). Mixtures containing fly ash continue to gain strength as it ages, especially during the first year after construction. At the time of the FWD test, the strength of fly ash stabilized CIR materials had not been completely developed. Therefore, further increases of strength and structural coefficient of base course are expected. More pavement performance monitoring will be performed in the coming years. The freeze-thaw durability of the fly ash stabilized CIR material will also be verified through long-term performance monitoring.
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