A multiscale model for mechanical and fracture behavior of calcium-silicate-hydrate: From molecular dynamics to Peridynamics

Abstract

Fully understanding the fracture behavior of concrete is a challenging work since concrete is a complex multiscale composite material with a heterogeneous structure at different length scales ranging from nanoscale to macroscale. A new multiscale model framework was proposed in the present study to explore the mechanical properties, including Young's modulus E and ultimate tensile strength UTS, and fracture behavior of calcium-silicate-hydrate (C-S-H) from the nanoscale to mesoscale. The nanoscale C-S-H globule models were built and simulated via molecular dynamics (MD) simulations and then the obtained mechanical properties were employed as the input parameters for the mesoscale Peridynamics (PD) simulations to acquire the E, UTS, and fracture behavior of C-S-H gel. The results reveal that at nanoscale, the mechanical performance of C-S-H is anisotropic: As the size of C-S-H model increases, the E and UTS of C-S-H decrease because the extension of crack in a larger C-S-H model will release more stored energy. At mesoscale as the packing fraction φ increases, the E and UTS of C-S-H gel increase. The resulted E and UTS are in line with former simulations and experimental data implying the effectiveness and accuracy of the proposed multiscale model.