Effects of nano-silica on hydration properties of tricalcium silicate

In order to evaluate the influence of nano-silica on tricalcium silicate (C3S) 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 C3S 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 C3S 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. (C) 2016 Elsevier Ltd. All rights reserved.