Molecular Dynamic Simulation of Failure of Ettringite

Abstract

Ettringite is an important component in the hydration products of cement paste. To better understand the failure modes under tensile loading of cement-based materials, mechanical properties of each individual hydration product needs to be evaluated at atomic scale. This paper presents a molecular dynamic (MD) method to characterize and understand the mechanical properties of ettringite and its failure modes. The molecular structure of ettringite is established using ReaxFF force field package in LAMMPS. To characterize the atomic failure modes of cement paste, MD simulations were conducted by applying tensile strain load and shear strain load, respectively. In each MD failure simulation, the stress-strain relationship was plotted to quantify the mechanical properties at atomic scale. Then elastic constants of the ettringite crystal structure were calculated from these stress-strain relationships. MD simulations were validated by comparing the mechanical properties calculated from LAMMPS and those acquired from experiments. Future research should be performed on bridging-relationships of mechanical properties between atomic scale and macroscale to provide insights into further understanding the influence of mechanical properties at atomic scale on the performance of cement-based materials at macroscale.