2D Mesoscale cracking simulation of partially saturated asphalt based on moisture diffusion and a cohesive zone model

Abstract

The primary objective of this paper was to develop a combined model that incorporates moisture diffusion and a cohesive zone model, addressing anisotropic and loading-rate dependent cracking within partially saturated asphalt. Utilising X-ray CT scan, cross-sectional slices of asphalt were acquired and converted into vector images through Matlab and AutoCAD, forming a digital asphalt sample. Moisture concentration in the asphalt, after different immersion durations, was quantified by Fick's law. A sequentially coupled model of moisture diffusion and fracture investigated the effect of immersion duration, anisotropy, and loading rate on cracking performance of the asphalt during a digital indirect tensile strength test (DITST) at 5°C. Findings revealed that moisture evolution in partially saturated asphalt proceeds through two or three stages: near-zero growth (only applicable for locations far from the initial moisture-asphalt interface), rapid growth, and a plateau. Peak load, stiffness, and fracture work in DITST exponentially reduced with immersion duration, predominantly within the first four weeks. Anisotropy led to differential DITST results when varying loading direction. Moisture damage decreased crack resistance across all directions, while increasing loading rate enhanced it. Fracture stiffness and strength exhibited comparable impacts on cracking performance at a specific loading rate.