Effects of nano-SiO2 particles on the mechanical and microstructural properties of ultra-high performance cementitious composites

In this research the effects of nano-SiO2 particles on the mechanical performance, hydration process and microstructure evolution of ultra-high performance cementitious composites were investigated by different methods. The results showed that the compressive and flexural strength increased with the increase of the nano-SiO2 content up to 3% and due to agglomeration of nano-SiO2 particles, the mechanical properties decreased slightly when the nano-SiO2 content was more than 3%. The hydration process was accelerated by the addition of nano-SiO2. The porosity and the average pore diameter decreased with the increase of the nano-SiO2 content and aging. The microstructure was more homogenous and dense for nano-SiO2 specimens as compared to the control specimen. All of these improvements could be mainly attributed to the pozzolanic and filler effects of nano-SiO2.