Effects of Aggregate Gradation and Asphalt Binder on the Visco-Elastic Behavior of Asphalt Matrix

Abstract

Asphalt matrix (AM) properties have been used for many years to relate the behavior and performance of Hot Mix Asphalt (HMA) mixture. The AM is commonly defined as the combination of asphalt binder and fine aggregates. Understanding the mechanics and rheological characteristics of AM can facilitate better mixture design, and provide an insight into the visco-elastic behavior of HMA mixtures. In this study, the effects of aggregate gradation and asphalt binders on the visco-elastic response of AM were studied. Two fine aggregate gradations and two asphalt types were used to make AM samples. Dynamic mechanical analyses were conducted to investigate the creep response and effect of rate of loading at various temperatures. The dynamic shear modulus (G*) and shear creep compliance (J[t]) were obtained over a range of temperatures to construct master curves at 25°C. The master curves for G* and J[t] were modeled using Sigmoidal function, and generalized visco-elastic model, respectively. The analysis of master curves and models showed that the finer gradation exhibited a lower G*, and higher J[t], for the neat binders. In general, the modified binders and coarser gradation produced a stiffer material for a range of frequencies, but the J[t] showed some variations in the AM creep response. In addition, rutting susceptibility of AM was evaluated using the Superpave® rutting parameter.