Experimental study of compression-tension asymmetry in asphalt matrix under quasi-static and dynamic loads via an integrated DMA-based approach

This research presents an experimental approach to study the mechanics of asphalt matrix, a crucial component in asphalt concrete, consisting of asphalt binder, fine aggregates and filler. Understanding its response is essential to guide and improve the new designs in advanced asphalt concrete. The proposed approach makes use of the dynamic mechanical analysis (DMA) to execute a variety of quasi-static and dynamic tests under tension and compression. Uniaxial tests reveal a remarkable compression-tension asymmetry of the asphalt matrix in terms of stiffness and strength. The peak stress and stiffness can be 5 and 3 times, respectively, larger under compression than in tension. Both properties strongly depend on the strain rate, albeit stiffness and peak stress in compression are more sensitive than in tension. A straightforward equation for the creep rupture envelop is derived by performing creep tests at different stress levels. Amplitude and frequency sweep tests and fatigue-recovery test are performed to explore the inherent self-healing capabilities of asphalt matrix at room temperature. Doubling the regularity of resting periods significantly helps to regain the stiffness and it leads to a 4-times extension of the fatigue life.