Combined effect of nano-SiO ₂ particles and steel fibers on flexural properties of concrete composite containing fly ash

Abstract This paper presents an experimental study to evaluate the combined effect of nano-SiO ₂ particles and steel fibers on flexural properties of concrete composites containing fly ash. In this study, five different nano-SiO ₂ contents (1%, 3%, 5%, 7%, and 9%) and five different steel fiber contents (0.5%, 1%, 1.5%, 2%, and 2.5%) were used. The results indicate that addition of nano-SiO ₂ and steel fibers decreases the workability of the concrete composites containing fly ash, and both the slump and slump flow decrease gradually with the increase in nano-SiO ₂ and steel fiber content. Besides, the addition of nano-SiO ₂ can greatly increase the flexural strength and flexural modulus of elasticity of concrete composites containing fly ash. There is a tendency for the increase in the flexural strength flexural modulus of elasticity with an increase in the nano-SiO ₂ content when the nano-SiO ₂ content is below 5%, while both of the two flexural parameters begin to decrease after the nano-SiO ₂ content above 5%. Furthermore, steel fibers have great improvement on the flexural properties of concrete composites containing fly ash and nano-particles. The flexural strength and flexural modulus of elasticity of concrete composites containing fly ash and nano-SiO ₂ are more than those of the concrete composite without steel fibers. Both of the two flexural parameters increase with the increase in steel fiber content when the steel fiber content is below 2%, while the flexural parameters begin to decrease after the steel fiber content is above 2%.