DESIGN AND CONSTRUCTION OF LARGE STONE HMA BASES IN KENTUCKY

Since Kentucky highways are subject to heavy coal-carrying truck traffic with truck factors in the range of 5 to 50 Equivalent Single Axle Loads per passage, a task force concluded that changes in the HMA base gradation could provide the needed improvement in shear resistance. These changes included a larger maximum particle size and higher percentage of coarse aggregate. Ten gradations with maximum particle sizes up to two inches were selected for laboratory testing prior to recommending gradation limits for field use. Design tests were run on several gradations, and a mixture was selected for additional tests. Specifications were produced for use in field projects. Details of The gradation specification identified as Type K base mixture are tabulated. Tests indicated improved design, and the strength properties were generally improved. The rutting resistance was approximately twice that of Kentucky's standard HMA base. The details are given of field projects constructed in 1988.