Mechanical properties of colloidal calcium-silicate-hydrate gel with different gel-pore ionic solutions : a mesoscale study

Abstract

The mechanical properties of hydrated cement paste are largely influenced by the interaction of nano-scale calcium-silicate-hydrate (C–S–H) particles that reside in the gel-pore aqueous ionic solution of colloidal C–S–H gel (C–S-Hgel). The ionic species and ionic concentration of the gel-pore solution can fluctuate – due to the hydration process of cement, the use of various admixtures, and ion exchange with the surrounding environment – and influence the dielectric constant (εr) of the gel-pore solution and the Debye length (κ−1). Mesoscale simulations were employed to investigate the mechanical properties of C–S-Hgel with gel-pore ionic solutions of different εr and κ−1. The results showed that εr and κ−1 influenced the packing density and cohesion of C–S-Hgel, and, in turn, its compressive stiffness, hardness, and strength. The lowest values of εr and κ−1 (i.e., highest ionic concentrations) resulted in higher stiffness, hardness, and strength. The information obtained in this study provided insight into the mechanism by which the gel-pore ionic solution affects the mechanical properties of C–S-Hgel and demonstrated that εr and κ−1 are useful parameters to consider when engineering design strategies for cementitious materials.