Utilization of an organic-inorganic composite type inhibitor to enhance interface between steel fibers and shotcrete

The steel fibers, due to remarkable crack resistance, are widely regarded was an effective technique of extending the service life of shotcrete structures applied in the submarine tunnels. However, few studies have focused on the effect of the interface between steel fibers and matrix on the durability of steel fiber-reinforced shotcrete (SFRS). This study aims to evaluate the adverse effects of steel fiber and improvement mechanism of an organic-inorganic composite type inhibitor incorporated SFRS. The results indicated that the presence of steel fiber can encourage calcium leaching from hydrated phases and moisture penetration, thereby leading to an increase in the surface spalling degree and the strength loss rate. Besides, the incorporation of 0.5 % steel fiber by volume respectively resulted in an increase of 100 % and 78.9 % in the count and volume of pores with diameter below 100 μm, indicating the formation of porous interface. Moreover, the addition of inhibitor into SFRS reduced the loss rate of compressive strength, delayed the calcium leaching process, and improved resistance to aggressive ion ingress. More importantly, a synergistic mechanism of carboxylate’s excellent hydrophobic effect and nano silica induced pore refinement remarkably reduces the calcium leaching induced decomposition of hydrated phases and the formation of corrosion products. • The adverse effect of interface surrounding steel fiber on the durability of shotcrete was evaluated. • The addition of 0.5 % steel fiber by volume led to an increase of 78.9 % in the volume of pores below 100 μm. • Synergistic effect of carboxylate’s hydrophobicity and nano silica induced pore refinement remarkably enhanced interface.