Computational modeling of shear deformation and failure of nanoscale hydrated calcium silicate hydrate in cement paste: Calcium silicate hydrate Jennite

Calcium silicate hydrate Jennite is a molecular structure commonly accepted as a representation of the complex calcium silicate hydrate gel formed during the hydration of typical Portland cement. In this paper, the behavior of nanoscale calcium silicate hydrate Jennite under shear deformation was investigated using molecular dynamics simulations. Computational samples representing the nanoscale structure of calcium silicate hydrate Jennite were subjected to shear deformation in order to investigate not only their mechanical properties but also their deformation behavior. The simulation results indicated that the nanoscale calcium silicate hydrate Jennite under shear deformation displays a linear elastic behavior up to shear stress of approximately 1.0 GPa, and shear deformation of about 0.08 radians, after which point yielding and plastic deformation occurs. The shear modulus determined from the simulations was 11.2 ± 0.7 GPa. The deformation-induced displacements in molecular structures were analyzed dividing the system in regions representing calcium oxide layers. The displacement/deformation of the layers of calcium oxide forming the structure of nanoscale calcium silicate hydrate Jennite was analyzed. The non-linear stress-strain behavior in the molecular structure was attributed to a non-linear increase in the displacement due to sliding of the calcium oxide layers on top of each other with higher shearing. These results support the idea that by controlling the chemical reactions, the tailored morphologies can be used to increase the interlinking between the calcium oxide layers, thus minimizing the shearing of the layers and leading to molecular structures that can withstand larger deformation and have improved failure behavior.