Three-Dimensional Mesomechanical Complex Modulus Prediction for Asphalt Mortar Considering Conjunctive Shell Mechanism of Interface Transition Zones and Properties of Coarse Mastic

Asphalt mortar is a mixture of asphalt mastic and fine aggregates (<2.36 mm) in asphalt concrete. Accurately predicting the complex modulus of asphalt mortar is essential to further estimating asphalt concrete’s viscoelastic properties. However, existing analytical and numerical mesomechanical models generally underestimate the dynamic moduli of asphalt mortar and overestimate its phase angles, especially at high temperatures and low frequencies, because the solidifying reinforcement mechanisms are not considered. Also, the commonly used mesoscale division method for asphalt mortar, which takes asphalt mastic as the matrix phase, may lead to computational inefficiencies due to the presence of numerous fine aggregates. To address these issues, this study proposed a coarse asphalt mastic-based three-dimensional (3D) mesostructure model of asphalt mortar considering a conjunctive shell mechanism of interface transition zones (ITZs). A new mesoscale division method was proposed for asphalt mortar, which defines the coarse mastic incorporating the aggregates smaller than 0.6 mm as the matrix phase. A conjunctive shell mechanism of ITZs was proposed to account for the solidifying reinforcement effect due to the overlapped ITZs of closely adjacent aggregates. The results indicate that the overlapped ITZs led to the formation of the agglomeration networks of aggregates. The introduction of conjunctive shell mechanism of ITZs enabled accurate prediction of the complex modulus of asphalt mortar even at low frequencies and high temperatures and revealed the solidifying behaviors of asphalt mortar. The computational efficiency was substantially improved by introducing the coarse mastic matrix.