The iowa department of transportation began creep and resilient modulus testing of asphalt concrete mixtures in 1989. Part 1 of thisresearch, reported in january 1990, was a laboratory study of hot-mix asphalt mixtures made with 0, 30, 60, 85, and 100% crushed gravel, crushed limestone, and crushed quartzite combined with uncrushed sand and gravel. Creep test results from marshall specimens related well to the percent of crushed particles and the perceived resistanceto rutting. The objective of this research, part 2, was to determine if there was a meaningful correlation between pavement rut depth and the resilient modulus or the creep resistance factor. Cores with 4- and 6-in. Diameters were drilled from rutted primary and interstate pavements and from interstate pavements with design changes intended to resist rutting. The top 2 1/2 in. Of each core, most of whichwas surface course, was used for creep and resilient modulus testing. There is a good correlation between the resilient modulus of 4- and 6-in.-Diameter cores. Creep resistance factors of 4- and 6-in.-Diameter cores also correlated well. There is a poor correlation between the resilient modulus and the creep resistance factor. The rut depth per million 18, 000-lb equivalent single-axle loadings for these pavements did not correlate well with either the resilient modulus or the creep resistance factor. This paper appears in transportation research record no. 1307, Pavement analysis, design, rehabilitation, and environmental factors 1991.
Abstract