Comparison of Aggregate Gradation and Mixture Physical Properties to Performance Tests of Coarse-Graded Superpave Mixtures in Louisiana

摘要

This paper presents the comparison of laboratory performance tests of coarse-graded Superpave HMA mixtures in Louisiana with physical properties of mixtures including volumetrics, aggregate gradation analysis, and field performance. Eight Superpave HMA mixtures were evaluated. Six of the eight mixtures were designed for high-volume traffic (greater than 30 million ESALs), while the other two mixtures were designed for low-volume traffic (less than 3 million ESALs). Theses mixtures includes two aggregate types: limestone and sandstone, and two binder types: PG 70-22M and PG 76-22M. Laboratory mechanistic tests conducted include indirect tensile (IT) strength, IT and axial creep, frequency sweep at constant height (FSCH) and repeated shear at constant height (RSCH). The aggregate gradation analysis was characterized using a Power-law to evaluate the effects of gradation on mixture mechanistic properties. Laboratory test results showed that high-volume mixtures appeared to have higher IT strengths, lower IT and axial creep slope and higher shear stiffness when compared to those of low-volume mixtures. This indicates that high volume mixtures generally possessed better rut-resistance than low volume mixtures considered. All four Power-law gradation parameters (a_(CA), n_(CA), a_(FA) and n_(FA)) were sensitive to the mixture mechanistic properties evaluated.