GPU-based discrete element model of realistic non-convex aggregates: Mesoscopic insights into ITZ volume fraction and diffusivity of concrete

Aggregates with realistic non-convex morphologies and their surrounding interfacial transition zones (ITZs) significantly affect the diffusivity of concrete. Herein, we initially propose a mathematical-controllable parameterized method to devise three-dimensional (3D) non-convex aggregates. Then, we develop a GPU-based discrete element modelling (DEM) to generate random close packing of polydisperse non-convex aggregates. Next, we establish three-phase concrete mesostructures containing non-convex aggregates and ITZs and obtain the ITZ volume fraction by a Monte Carlo random point sampling method. Finally, we develop a dual-probabilityBrownian motion (DP-BM) scheme to obtain the effective diffusivity of concrete. Moreover, the effects of volume fraction, size polydispersity and shape of aggregates as well as ITZ thickness on the ITZ volume fraction and concrete diffusivity are researched to probe rigorous component-structure-property relations for concrete. This work provides a comprehensive numerical framework for mesostructure characterization and diffusivity evaluation for concrete, which can be a valuable tool for durability assessment of concrete.