Prohibiting pure and saline water infiltration into organic-nano-coated calcium silicate hydrates surface: A nanoscale mechanisms analysis

Abstract

Extend the lifetime of coated cement paste under severe environment is a big challenge and the most crucial problems are related the degradation in the interface between coating and cement paste. This work is devoted to an in-depth investigation under aggressive environment of the deterioration process between epoxy coating and nano-granular Calcium-Silicate-Hydrate (CSH) paste. Further, a depth analyze of what properties make an organic-coating (epoxy and rubber) impermeable is established by means of Molecular Dynamics simulations (MD). Results indicate that the chlorine ions are responsible to attack the epoxy resins coating and CSH surface. Non-fully epoxy coating is detached more distorted in salty solution (4 wt% of NaCl) than in pure water solution. The Casurface-Oepoxy and Casurface-NMPD are the two bonds responsible for the bonding strength of epoxy resins coating and CSH surface. It is found that both the pore structure and the big surface roughness in organic-coating could accelerate the degradation in the interface. The water sorption in the permeable epoxy coating is increasing within time, in agreement with experimental investigations. Nevertheless, a continuous well-distributed rubber nano-coating is capable to make CSH impermeable under harsh environment. The obtained diffusion coefficient is decreased by 12.26 % in 4 wt% of NaCl solution.