Nano-scale mechanics of coarse-grained C-S-H with molecular dynamics

The strength of concrete is largely controlled by colloidal calcium-silicate-hydrate (C-S-H) gel. However, the mechanical behavior of calcium-silicate-hydrates (C-S-H) is still an enigma that has deceived many decoding attempts from experimental and theoretical sides. In this paper, based on coarse-grained mesoscale simulations, we investigate the mechanical properties of polydisperse C-S-H based on statistical theory. Our simulations offer a good agreement with nanoindentation data over a large range of packing fraction. The results show that, the bulk modulus and indentation modulus of C-S-H colloidal structure are closely related to packing fraction, and show significant linear positive correlations. The results are confirming and extending the existing data. Furthermore, the grain size significantly affects the packing fraction, and the packing fraction of C-S-H colloidal structure can be improved by decreasing the minimum grain diameter or increasing the maximum grain diameter. So, increase the range of grain diameter can improve the packing fraction of C-S-H structure signifi-cantly, so as to strengthen its mechanical properties.