Insights at the neutron irradiation-induced structural homogenization effect of calcium silicate hydrates and degradation mechanism of mechanical properties: a molecular dynamics study

Concrete has been widely applied in nuclear facilities, however, knowledge about the degradation mechanisms of cementitious materials due to irradiation is still limited. Therefore, in this work, molecular dynamics was employed to investigate the influence of irradiation energy on the structure and mechanical performance of calcium silicate hydrates (C-S-H, primary hydration products of Portland cement). Simulation results indicate irradiation leads to an isotropic structure transformation of C-S-H. The strength and stiffness of C-S-H along the in-plane direction was substantially reduced by irradiation, regardless of compression or tension loading. It is caused by the shortening of mean chain length of silicate tetrahedra, as well as the increase in the number of cracks and pores. Furthermore, an increase in the ductility of C-S-H is also observed, which is related to reorganizations and re-polymerizations of silicate tetrahedra on high-stress conditions. The mechanisms interpreted here pave the way to designing more irradiation-resistant cement-based materials.