Effect of silica fume on fracture properties of high-performance concrete containing fly ash

Abstract

A parametric experimental study has been conducted to investigate the effect of silica fume on the fracture properties of high-performance concrete containing fly ash, with four silica fume contents (3%, 6%, 9% and 12%) used. By means of three-point bending method, the fracture toughness, fracture energy, effective crack length, critical crack opening displacement and maximum crack opening displacement of the specimen were measured, respectively. The results indicate that silica fume has great adverse effect on the fracture toughness, fracture energy, effective crack length, critical crack opening displacement and maximum crack opening displacement, and these fracture parameters decrease gradually when the content of silica fume increases from 3% to 12%. Besides, as the silica fume content increases from 3% to 12%, the relational curves between the vertical load and the mid-span deflection (P_V–δ), crack mouth opening displacement (P_V– $\mathrm{CMOD}$ ) and crack tip opening displacement (P_V– $\mathrm{CTOD}$ ) are becoming thinner and thinner, which indicates that the capability of high-performance concrete containing fly ash to resist crack propagation is becoming weaker and weaker. It seems that the content of silica fume of high-performance concrete containing fly ash should be controlled strictly, and the silica fume content should be as low as possible on condition that the other properties of high-performance concrete can meet practical requirements.