Fatigue characterization of porous asphalt mixture complicated with moisture damage

Abstract

This study investigated the fatigue behavior of a porous asphalt mixture (PAM) considering the effect of moisture damage. The PAM was designed with a high-viscosity asphalt and target air void of 20%. Moisture damage was induced through freeze–thaw (F-T) conditioning with 1, 3, 5, 10, and 15 cycles, and was quantified in terms of loss in the indirect tensile (IDT) strength. The IDT fatigue test with the single- and two-stage loading patterns was employed. Results indicated that the strength decreased with the number of F-T cycles following an exponential decay function. Moisture damage rendered the PAM more susceptible to fatigue loading, and at higher stress levels the material exhibited higher fatigue dependence on moisture damage. In the S-N relationships established from the single-stage fatigue characterization, the role of moisture damage was incorporated into the intercept and slope as exponential functions. The two-stage characterization resulted in the Miner’s sum M < 1 for the high-to-low loading sequence, and M > 1 for the low-to-high sequence. The power-law nonlinear damage rule was adopted, in which the dependence of the exponent on moisture damage was found to follow an exponential decay function. In the predictive models developed for both loading patterns, the effects of moisture damage and loading level were mathematically described in uncoupled forms, as a result of no moisture damage progression during fatigue loading.