Simulation study on the impermeability improvement effect of cement-based materials with different pore structures

The impermeability of cement-based materials is the first line of defence for ensuring durability. Improvements in the impermeability of cement-based materials can be achieved by optimising their pore structure. However, the mechanism by which the improvement in impermeability of cement-based materials varies with their initial porosity remains unclear and requires systematic research. In this study, a simulation method was used to investigate this mechanism. It was found that for cement-based materials with different initial porosities, when the reduction in porosity resulting from pore structure optimisation was within the range of 0.8%-7%, as the initial porosity increased from 10.1% to 38%, the improvement in impermeability increased from 1.1% to 19.6% when the connectivity of the pore structure remained unchanged, and from 1.3% to 24.3% when the connectivity of the pore structure weakened. A mathematical relationship between the impermeability improvement effect and pore structure characteristics, including initial porosity, porosity reduction, and pore structure connectivity, was established, forming a macroscopic mechanism model for the impermeability improvement effect. According to this model, the macroscopic mechanism of nano-modified cement-based materials reveals that nano silica has more significant modification effects on the pore structure of cement-based materials with lower initial porosities.