Effects of nano-silica on hydration properties of tricalcium silicate

• Published in: Construction & building materials 2016-10, Vol.125, p.1169-1177
• Main Authors: Xu, Zhenhai, Zhou, Zonghui, Du, Peng, Cheng, Xin
• Format: Article
• Language: English
• Subjects: Analysis; C3S; Ca(OH)2 content; Concrete; C–S–H gel; Hydration rate; Mechanical properties; Nano-silica; Pore size distribution; Silicates
• ISSN: 0950-0618; 1879-0526
• DOI: 10.1016/j.conbuildmat.2016.09.003

•Nano-silica accelerates C3S hydration in 3d but reduces hydration rate after 3d.•Nano-silica increases C–S–H content but reduces growth rate of C–S–H after 3d.•Denser C–S–H with low Ca/Si ratio is formed in the presence of nano-silica.•Nano-silica reduces the total porosity of C3S and optimizes the pore structure. 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 3d but slows down in the later age (7d, 28d and 60d). C–S–H content increases with the increase content of nano-silica. However, an obvious reduction in C–S–H increment occurs at 7d, 28d and 60d. In addition, the hydration products morphology changes from rod-shape to dense matrix at 28d after nano-silica modification, and the Ca/Si ratio of C–S–H gel decreases. Besides, the addition of 3wt.% 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.