Synergistic effect of surfactant and chlorine salt on dispersion of nano-SiO2 and performance of cement-based grout containing a large amount of bentonite

Nano-SiO2 (NS) is widely used to improve the performance of cement-based grouts. The workability and mechanical property of grouts are greatly affected by NS dispersion. In this paper, synergistic effect of surfactants and chloride salts on NS dispersion, as well as on performance of grouts including fluidity, mechanical and microscopic properties were systemically studied. The results showed that the synergistic effect of anionic surfactant (SDS) and chloride salt can effectively improve NS dispersion because of the massive formation of micelles that can encapsulate NS and the electrostatic repulsion between micelles. And the effect of CaCl2 was more significant than NaCl. Furthermore, fluidity of fresh slurry and mechanical property of hardened grouts were also improved by the synergistic effect. The mechanical property enhancement might be attributed to the filling effect of NS due to its improved dispersion, and to the matrix compaction associated with the formation of strätlingite and Friedel's salt.