Effect of Gradation on Asphalt Mixture Performance

Abstract

Phase I of National Pooled Fund Study No. 176, “Validation of Strategic Highway Research Program (SHRP) Asphalt Mixture Specifications Using Accelerated Testing,” has been completed. One of the topics addressed in this project was the effect of gradation on asphalt mixture performance. The purpose of Phase I was to evaluate sensitivity of tests to changes of gradations within the framework of Superpave aggregate specifications. Tests included in the study were prototype scale accelerated pavement tests, laboratory scale wheel-tracking tests, and triaxial tests. Mixtures reported on here included one asphalt (PG 64-22), one coarse aggregate (limestone), and one limestone sand (fine aggregate angularity value of 44). Mixtures in the study have gradations above, through, and below the restricted zone. Results indicate that tests used are sensitive to changes in gradation and aggregate types.