A Comparative Study on the Pozzolanic Activity between Nano-SiO_2 and Silica Fume

摘要

The pozzolanic activity of nano-SiO_2 and silica fume was comparatively studied by X- ray diffraction (XRD), differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and the com-pressive, bond and bending strengths of hardened paste and concrete were also measured. Results indicate that the compressive strength development of the paste made from Ca (OH)_2 and nano-SiO_2, the reaction rate of Ca (OH)_2 with nano-SiO_2 and the velocity of C-S-H gel formation from Ca(OH)_2 with nano-SiO_2 showed marked increases over those of Ca(OH)_2 with silica fume. Furthermore, the bond strength at the interface between aggregate and hardened cement paste, and the bending strength of concrete incorporated with. 3 percent NS increased more than those with SF, especially at early ages. To sum up, the pozzolanic activity of nano SiO_2 was much greater than that of silica fume. The results suggest that with a small amount of nano-SiO2, the Ca (OH)_2 crystal at the interface between hardened cement paste and, aggregate at early ages may be. effectively absorbed in high performance concrete.