Surface-Modified Steel Fiber: Fabrication, Mechanical Properties, and Corrosion Resistance

Abstract In order to enhance the interfacial bonding between steel fibers and cement-based materials, a modified solution was prepared by 3-aminopropyltriethoxysilane (KH-550) and tetraethyl orthosilicate (TEOS) using the sol-gel method. The effect of relative concentration of KH-550 on pullout properties and microstructure of surface coating was studied. Moreover, corrosion resistance in three kinds of solutions (NaCl, <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"> <mml:mrow> <mml:msub> <mml:mi>Na</mml:mi> <mml:mn>2</mml:mn> </mml:msub> <mml:msub> <mml:mi>SO</mml:mi> <mml:mn>4</mml:mn> </mml:msub> </mml:mrow> </mml:math> , and HCl) of modified steel fibers was also discussed. The results showed that the effectiveness of silane coupling agents in modifying the surface of steel fibers was influenced by the relative concentration of KH-550. When the relative concentration of KH-550 was low, the adhesion of the coating to steel fiber surface was poor. Conversely, excessively high concentrations increased coating thickness but make it prone to cracking. When the KH-550/TEOS ratio was 3, the surface coating exhibited high smoothness, minimal cracks, and excellent adhesion. In addition, the ultimate pullout load, pullout energy consumption, and bond strength of modified steel fibers all reached more than 170% compared to that of untreated samples. In corrosive environments, the mass loss rate and the performance in pullout tests of modified steel fibers showed far smaller reductions compared to untreated steel fibers. Moreover, the difference in corrosion resistance became more pronounced over time due to the interfacial bonding and effective physical barrier provided by the modification.