Effect of Nanosilica on interfacial bond strength of steel fiber embedded in ultra high performance concrete

Abstract

This study investigated the influence of nanosilica (NS) content on the interfacial bond strength of steel fiber embedded in ultra high performance concrete (UHPC). When replacing the cement content with the corresponding NS content from 0.5 to 2.0% in the mix composition of UHPC, the interfacial bond strengths of steel fiber embedded in UHPC significantly increased and achieved the highest value as using 1.0% NS content. The maximum (τ_peak) and equivalent (τ_eq) bond strengths were 13.63 MPa and 140.10 MPa, respectively. The bond strengths of UHPC were enhanced owing to the addition of NS to UHPC increasing the density at the interfacial transition zone around the surface of steel fiber and UHPC. In addition, as NS content was increased from 0.5 to 1.0%, the compressive strength of UHPC enhanced and reached the highest value (201.51 ± 3.40 MPa) at 1.0% NS content. However, the compressive strength of UHPC decreased as the NS content was between 1.0 and 2.0%. Furthermore, adding NS to the mix composition reduced the workability of UHPC. The flowability of the UHPC containing NS contents was all lower than 235 mm, while the flowability of the control specimen was 245 mm.