From atomic-scale to mesoscale: A characterization of geopolymer composites using molecular dynamics and peridynamics simulations

A multiscale approach that couples molecular dynamics (MD) and peridynamics (PD) simulations was implemented to study the mechanical behavior of geopolymer composites (GC) consisting of geopolymer binder (GB), calcium silicate hydrate (CSH) and quartz. Using MD, intrinsic mechanical properties such as bulk modulus, shear modulus and strain energy release rates were determined for the constituent phases as well as the respective two-phase systems. The MD generated properties were then used to determine the input parameters for PD simulations. Both bond-based and state-based PD models were considered for simulating the GC. The first part of the PD study consisted of characterizing the properties of mesoscale porous GB. Interestingly, the predicted modulus of porous GB at porosities corresponding to experimental values compared well with experimental observations based on nanoindentation (NI). NI tests were also conducted using PD simulation to predict the hardness of GB, which was also consistent with experimental data. Finally, PD simulations of mesoscale GC consisting of multiple GB, CSH and quartz (010) domains showed that the presence of quartz (010) increases its strength. It was also observed that the strength of GC increased with increasing domain-sizes of the constituent phases, which can be compared to inverse Hall-Petch effects in nano-crystalline materials.