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

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-H-gel). 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 (epsilon(r)) of the gel-pore solution and the Debye length (kappa(-1)). Mesoscale simulations were employed to investigate the mechanical properties of C-S-H-gel with gel-pore ionic solutions of different epsilon(r) and kappa(-1). The results showed that epsilon(r) and kappa(-1) influenced the packing density and cohesion of C-S-Hgel, and, in turn, its compressive stiffness, hardness, and strength. The lowest values of epsilon(r) and kappa(-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-H-gel and demonstrated that epsilon(r) and kappa(-1) are useful parameters to consider when engineering design strategies for cementitious materials.