Surface reaction, water diffusion and mechanical properties of hydrated nanoporous calcium aluminosilicate gel structures

A hydrated porous gel-like structure rich in silica is usually formed at the glass-water interface during the corrosion of silicate or borosilicate glasses. Understanding the chemical reactions and material transport in this amorphous interfacial layer is considered critical to design glasses with long term chemical durability for various technological applications. We have used large scale reactive molecular dynamics simulations with relaxation time up to 25 nano-seconds to generate hydrated nanoporous calcium aluminosilicate gel structures with different porosities and pore morphologies by using sequential hydration and hydrolysis reactions. The results provide insights into atomic and microstructures, surface and interfacial reactions, and mechanical properties of these gel structures that are difficult to directly access experimentally. It was found that the morphology and pore size distribution play a major role in the diffusion of water and mechanical strength in these gel structures, while the short-range structures of the gels are mainly controlled by the compositions of gel. The findings were compared and discussed with experimental observations.