Enhancing fiber–matrix interfacial bond in ultra-high-performance concrete containing titanium dioxide

Abstract

This study investigated the interfacial bond behavior of straight steel fiber in ultra-high-performance concrete (UHPC) containing titanium dioxide (TiO2) as an alternative to silica flour. Experiments were conducted for five replacement ratios (i.e., 0%, 25%, 50%, 75%, and 100%) of TiO2. The results indicated a significant improvement in the bond performance of the steel fiber of UHPC containing TiO2. The best performance was exhibited by the 50% replacement ratio specimen, which showed the highest average bond strength and pullout energy of 7.22 MPa and 447.9 mJ, respectively. Although the benefits of adding TiO2 decreased beyond the replacement ratio of 50%, the 100% replacement ratio specimen demonstrated higher bond strengths and pullout energy than those without TiO2. Thus, TiO2 helps suppress the pullout of steel fiber from UHPC more effectively, which was verified by the presence of severe surface scratches on the steel fiber.