Fracture resistance of ultra-high-performance fiber-reinforced concrete containing nanoparticles at high strain rates

Abstract

The fracture resistance of ultra-high-performance fiber-reinforced concrete (UHPFRC) containing various types of nanoparticles (NPs) under various strain rates (0.000333–156.55 s−1) was investigated. Four matrices were examined: UHPFRC without NPs (UM), UM containing 3% nano-CaCO3 (UC), UM containing 1% carbon nanotubes (UCNT), and UM containing 1% nano-SiO2 (US). The effects of the strain rate on the fracture resistance of the matrices, including fracture strength, fracture energy, and specific work-of-fracture (WS), were evaluated. All matrices containing NPs demonstrated a higher rate-sensitive fracture resistance than that of the UM matrix. The dynamic increase factors (DIF) for the WS of UC, US, and UCNT were 4.50, 4.30, and 3.68, respectively, whereas that of UM was the lowest at 3.44. Of the NP-containing UHPFRCs, at high strain rates between 140.6 and 156.55 s−1, the matrices arranged in order of decreasing WS magnitude are UC > US > UCNT. The fracture resistance enhancement in UC was attributed to the improvement in the C-S-H content of the fiber–matrix zone due to the added nano-CaCO3, which increased the interfacial bond strength of the smooth steel fibers embedded in the UHPFRC.