Effect of pores and moisture on the mechanical properties of calcium silicate hydrate gels at mesoscale

Pores and moisture significantly influence the mechanical properties of cementitious materials. Investigating the effects of pores and moisture on the mechanical properties of calcium silicate hydrate (C-S-H) gels at the mesoscale is fundamental to understanding the multiscale behavior of these materials. In this study, mesoscopic models of C-S-H gels with varying porosities were developed using coarse-grained C-S-H nanoparticles. The potential function, describing the interaction between C-S-H nanoparticles under different humidity conditions, was derived based on the mechanical properties of C-S-H nanoparticles, the Lennard-Jones (LJ) potential, and capillary theory. Subsequently, simulations of uniaxial tensile, uniaxial compression, and shear experiments on C-S-H gels with different porosities and moisture levels were conducted. The influence of pores and moisture on the mechanical properties of C-S-H gels was analyzed using two-way analysis of variance (ANOVA) and then compared with mesoscopic influence patterns. The results showed that the mechanical properties of C-S-H gels decrease with increasing porosity and moisture at the mesoscale. And there is an interaction effect between gel pore porosity and moisture. The smaller the porosity, the more significant the weakening effect of increasing moisture on elastic parameters and strength. Conversely, the weakening effect of increasing porosity on elastic parameters and strength is more significant at lower moisture levels. The interaction between pores and moisture has a more pronounced effect on strength, which intensifies with increased moisture. The effect of porosity on the mechanical properties of C-S-H gels is consistent with macroscale studies. However, the effect of moisture on elastic parameters exhibits an opposite trend, attributed to the different mechanisms of water's influence at different scales.