Effect of Nano-SiO2 Particles on Fracture Properties of Concrete Composite Containing Fly Ash

A parametric experimental study has been conducted to investigate the effect of nano-SiO₂ particles on fracture properties of concrete composite containing fly ash. Five different nano-SiO₂ contents were used for this study. By means of three-point bending method, the fracture parameters of the effective crack length, initial fracture toughness, unstable fracture toughness, fracture energy, critical crack opening displacement, maximum crack opening displacement and maximum mid-span deflection of the beam specimen were measured. The results reveal that the addition of lower SiO₂ content (<5%) nano-particles may help improve the fracture properties of concrete composite containing fly ash. Nano-SiO₂ has a significant effect on the fracture relational curves of the three-point bending beam specimen. The fracture parameters increase gradually and the fracture relational curves become thicker as the nano-SiO₂ content increases from 0% to 5%. However, the fracture parameters begin to decrease and the curves become thinner when the nano-SiO₂ content exceeds 5%. These variation rules of fracture parameters and fracture relational curves indicate that nano-SiO₂ contributes significantly to the improvement of fracture properties of concrete composite containing fly ash only when its content does not exceed 5%.