Effects of nano-silica on hydration properties of tricalcium silicate

In order to evaluate the influence of nano-silica on tricalcium silicate (C 3 S) hydration, hydration rate, Ca(OH) 2 content, quantification of C–S–H, pore size distribution and micrographs of hydration products were measured. Results revealed that with the increase content of nano-silica, the hydration of C 3 S is accelerated before hydration for 3   d but slows down in the later age (7   d, 28   d and 60   d). C–S–H content increases with the increase content of nano-silica. However, an obvious reduction in C–S–H increment occurs at 7   d, 28   d and 60   d. In addition, the hydration products morphology changes from rod-shape to dense matrix at 28   d after nano-silica modification, and the Ca/Si ratio of C–S–H gel decreases. Besides, the addition of 3   wt.% nano-silica can reduce the total porosity of C 3 S by 4.04% and optimize the pore structure. Furthermore, the density of paste increases by 4.22%, which finally leads to the more compact structure of hardened paste.