Research on Optimizing the Steel Fiber/CSH Interface Performance Based on Ca/Si Ratio

Steel fiber reinforced concrete in marine environments often suffers from stress corrosion coupling. Under mechanical loading, the formation of penetrating cracks in the matrix increases susceptibility to seawater penetration and interfacial degradation. Using molecular dynamics simulations, this study investigated the effects of calcium-to-silicon (Ca/Si) ratios on the interfacial bonding and transport properties of a γ-FeOOH/CSH system. The results show that higher Ca/Si ratios strengthen ionic bonding between CSH and γ-FeOOH, thereby improving interfacial adhesion. Additionally, increased Ca/Si ratios significantly slow the transport of water molecules and ions (Na⁺, Cl^-, SO₄^2-) within γ-FeOOH/CSH nanopores. It was observed that Cl^- and SO₄^2- exhibited pronounced filtration effects at Ca/Si = 2.0. These findings suggest that optimizing the Ca/Si ratio in concrete can simultaneously enhance interfacial strength and reduce permeability. This provides an effective strategy for improving the marine erosion resistance of steel fiber reinforced concrete structures.