Multi-scale analysis on fracture behaviors of asphalt mixture considering moisture damage

Moisture damage is a main factor degrading the bonding performance between asphalt binder and aggregate, playing adverse effects on the integrity of pavements, and thus reducing their serviceability substantially. The asphalt pavement is susceptible to moisture damage, exhibiting weakened durability and accelerated distress in many other formations with lower service life. In this study, moisture damage was reflected in the immersion method of Marshall test, and the deterioration potential of moisture damage on the fracture behaviors of asphalt mixture was investigated through multi-scale analysis. Pull -off tests were carried out to characterize the bonding performance between asphalt binder and aggregate considering the influence of moisture erosion, and the adhesion and cohesion results were adopted as the key mechanical parameters for the subsequent numerical analysis. Semi-circular bending (SCB) tests were conducted for the specimens with or without water immersion conditioning, and the fracture parameters, including the critical strain energy release rate (J -integral), Flexibility Index (FI), Crack Resistance Index (CRI), and Balanced Cracking Index (BCI), were obtained to provide insights into the fracture performance of the asphalt mixture. Furthermore, the mechanism of moisture affecting the fracture behavior of asphalt mixtures in meso-scale was explored through numerical analysis based on finite element modeling (FEM). A virtual SCB specimen integrated with two cohesive zone models (CZM) describing the failure of asphalt mortar and the loss of adhesion between asphalt binder and aggregate was established. The results from pull -off tests indicated that water immersion could enlarge the adhesive failure area and subsequently decrease the bonding strength between binder and aggregate. However, moisture damage had a limited effect on cohesive failure performance. Results from SCB tests showed that immersion could significantly increase the moisture damage potential and the crack development speed, weaken the fracture resistance, and reduce the flexibility of the asphalt mixture. The numerical analysis method proposed in the study was effective to interpret the effect of moisture damage on the fracture behaviors of the asphalt mixture. It was found that moisture damage led to more pronounced internal damage, and more failures at the interface of binder-aggregate were observed due to the deterioration effect of moisture erosion on the adhesion. According to the fracture development under dry and wet conditioning, the asphalt mixture would crack earlier after encountering moisture damage. The research method combining laboratory tests and numerical simulations demonstrated more comprehensively the impact of moisture damage on the fracture performance of asphalt mixture from a macro to meso perspective.