Influence of ground quartz sand finesses on the formation of poorly ordered calcium silicate hydrate prepared by dynamically hydrothermal synthesis

This study aimed to prepare poorly ordered calcium silicate hydrate (C-S-H) via the hydrothermal synthesis method, using ground quartz sand powder and lime as starting materials. The fineness of quartz sand powder under different grinding time and varied grinding aids content was investigated. It further affected the formation of calcium silicate hydrate. Results showed that the main synthesized product was crystalline dicalcium silicate hydrate (C2SH) with a small amount of C-S-H when quartz sand was ground to 29.95 μm for D50, attributed to the coarse particle size with a low silica reaction rate. Increasing the grinding time and grinding aid content of quartz sand improved the silica reaction rate and accelerated the formation of calcium silicate hydrate. Adding 1‰ grinding aid content would greatly improve the grinding efficiency, and the particle size of quartz sand powder was greatly reduced to the smallest value recorded in this study (D50 was 21.08 μm), which was beneficial to the transformation of C-S-H from C2SH. Meanwhile, C-S-H underwent a change from having a flocculated morphology to a needle-like, short-rod-like and fibrous morphology.