TY - JOUR TI - Fracture modeling of asphalt concrete with heterogeneous microstructure DO - https://doi.org/doi:10.7282/T3C24Z5J PY - 2015 AB - Understanding fracture resistance of asphalt concrete is of great importance in designing pavements with long service life. This thesis focused on studying the micro and global fracture behavior of heterogeneous asphalt concrete with a numerical analysis approach. Finite element (FE) models were built with the capacity of taking heterogeneity into consideration. The asphalt concrete was modeled as a multi-phase material with coarse aggregates and fine aggregate matrix (FAM). Viscoelastic properties were assigned to the FAM. Different damage models were incorporated to study fracture at two length scales: micro-fracture within FAM and coarse aggregate-FAM interface under small displacement and global fracture resistance in the semi-circular bending (SCB) test. For micro-fracture simulation, asphalt mixture was modeled with both adhesive and cohesive failure potential. Two different fracture models, cohesive zone model (CZM) and extended finite element model (XFEM), were adopted to simulate fracture damage within the FAM (cohesive failure) and at the FAM-aggregate interface (adhesive failure), respectively. For global fracture properties, the SCB test was simulated to predict the crack propagation pattern and the load-crack mouth opening displacement (CMOD) curve of asphalt concrete. Parametric studies with different material properties of FAM and coarse aggregates-FAM interface, morphological characteristics of coarse aggregates, and testing conditions (loading rate and temperature) were carried out to study their effects on fracture behavior of asphalt concrete. The numerical models provide an effective method to study fracture mechanism of heterogeneous asphalt concrete and generates meaningful findings. The development of cracking shows that the damage in the FAM material would initiate first at a small displacement and then interconnect with the damage developed at the FAM-aggregate interface. The higher angularity and larger aggregate size induces the greater damage level; while the orientation angle along with aspect ratio has influence on the anisotropic behavior of asphalt concrete. On the other hand, the SCB test simulations show good agreements with experimental results in the literature. Increasing fracture strength and energy of FAM significantly improves fracture resistance of asphalt concrete. The spatial distribution and angularity of coarse aggregate affect crack path; while the gradation and size of coarse aggregate affect fracture strength of asphalt concrete. KW - Civil and Environmental Engineering KW - Asphalt concrete KW - Aggregates (Building materials) KW - Fracture mechanics LA - eng ER -