Many factors affect the properties of asphalt concrete, and one of these is the maximum aggregate size used in the mix. A laboratory analysis of the effect of varying the maximum aggregate size on rutting potential and on other properties of asphalt aggregate mixtures was performed. The aggregate in all mixes evaluated consisted of 100% crushed limestone. The five different mix designs evaluated included aggregate having gradations that contained maximum aggregate sizes of 3/8, 1/2, 3/4, 1, and 1 1/2 in. The asphalt content for all mixes was selectedto provide an air voids content of 4% under a compactive effort in the gyratorytesting machine equivalent of 75 blows of a marshall hammer. All mixes producedwith the five gradations were subjected to a testing program that included tests to evaluate marshall stability and flow, indirect tensile strength, creep, andresilient modulus. Specimens for mix design and evaluation of mixture properties were compacted in a 4-in. Diameter mold. In addition, specimens at optimum asphalt content were prepared in a 6-in. Diameter mold and were tested by using theindirect tensile test and the creep test. These results were then compared to those from the 4-in. Diameter specimens for the same aggregate gradations. Test results indicated that mixes with larger aggregate design with an air voids content of 4% were generally stronger than mixes prepared with smaller aggregate. Themixes with larger aggregate also required significantly less asphalt. This paper appears in transportation research record no. 1259, Chip seals, friction courses, and asphalt pavement rutting 1990.
Samenvatting