Coupling Effect of Abrasion and Erosion on Ultrahigh-Performance Seawater–Sea Sand Concrete

Preparing ultrahigh-performance seawater–sea sand concrete (UHPSSC) to mitigate the scarcity of freshwater and river sand resources has generated considerable recent research interest. However, the deterioration mechanisms of UHPSSC under the effect of abrasion and erosion remain unstudied. In this paper, the underwater steel ball method was conducted to evaluate the impact of seawater, sea sand, steel fiber, and seawater abrasion on the abrasion resistance of UHPSSC. Then the stress erosion models of calcium–silicate–hydrate (C-S-H) were constructed to investigate the degradation mechanisms of UHPSSC under the effect of external stress and seawater erosion. The results show that the application of seawater and untreated sea sand leads to a reduction of 12.6% in the abrasion resistance strength. The steel fibers can form the fiber skeleton network in the matrix, which improves the abrasion resistance strength by 67.4%. The coupling effect of abrasion and erosion ions in seawater has caused a reduction (by 12.0%) in the abrasion resistance strength of UHPSSC and the corrosion of steel fibers. Molecular dynamics (MD) simulations show that under the NaCl solution environment, the tensile strength, critical energy release rate, and fracture toughness of C-S-H decreased by 21.5%, 19.3%, and 10.8%, respectively. NaCl solution entered into the interlayer and weakens the chemical bonding interactions and the interlayer cohesion of C-S-H. This paper has prepared UHPSSC material with excellent abrasion resistance and provided a nanoscopic degradation process of UHPSSC under seawater abrasion.