Experimental Investigation of Rest Time Effect on Permanent Deformation of Asphalt Concrete

Abstract

Asphalt concrete is a complex mixture, the behavior of which is dependent on its components while showing different nonlinear behaviors under various conditions. Application of rest time between compressive loading cycles causes hardening-relaxation (H-R) behavior in the sample and increases the deformation potential of the sample. This process might induce changes in the microstructure and the pattern of the placement and rotation of the aggregates. These changes cause a relaxation in the hardening of the material, pose a higher potential of reception of viscoplastic strain in the following cycles, and increase the rate of accumulation of the permanent deformation in contrast with creep loading. On the other hand, corresponding to the inherent properties of bitumen, it causes improvement (healing) in material properties which ultimately will increase the fatigue life. Thus, the aim of this study is to investigate the deformation of asphalt concrete material under compressive loading along with different rest times, by considering both H-R and healing (h) behaviors. In this experimental study, the behavior of hot mixed asphalt (HMA) under different loading conditions is investigated (at 25°C temperature). This study shows that application of longer rest times reduces the effect of H-R behavior and increases the potential of healing, thereby reducing the amount of deformation in the samples, while with shorter rest times the effect of H-R is more prominent and HMA samples experience more permanent deformation.