Investigations on the development of powder concrete with nano-SiO₂ particles

Abstract

The nano scale of particles can result in dramatically improved or different properties from conventional grain-size materials of the same chemical composition. Therefore, it is practical to add nano-silica in particle form with 99.9% of SiO₂ in nano scale to improve the characteristics of cement mortar. The compressive strengths of cement mortar were evaluated at various water-cementitious ratio. Five different water-cementitious ratios were used including, 0.23, 0.25, 0.32, 0.35, and 0.48 and four contents of nano-SiO₂ particles, 3%, 6%, 9%, and 12% by weight of cement. The compressive strength of cement mortar with the addition of silica fume were also evaluated at w/cm ratio of 0.48 to compare with mortar containing nano-SiO₂ particles and three contents of silica fume were: 5%, 10% and 15% by weight of cement. The experimental results show that the compressive strengths of mortars with nano-SiO₂ particles were all higher than those of mortars containing silica fume at 7 and 28 days. It was demonstrated that the nano-particles were more valuable in enhancing strength than silica fume. This paper also analyzed some available examinations to monitor the hydration progress continuously, such as SEM observation, residual quantity test for Ca(OH)₂ and the rate of heat evolution. The results of the examinations indicate that the SiO₂ in nano scale behave not only as a filler to improve the microstructure, but also as an activator to promote pozzolanic reactions.