Experimental Investigation of Sand-Nanosilica Mixture under Long-Term Unfavourable Environments

Colloidal nanosilica is a new kind of chemical grout material for filling the small gaps of fine-grained soil. Compared to traditional material-silicate sodium, which has been synonymous with "chemical grout" for many years, the advantages and disadvantages of colloidal nanosilica should be studied. In this paper, permanence is the focus. Hence, laboratory test was adopted to study the stability of the pure gels and long-term effect of sand-gel mixtures of the two materials. Samples of Fontainebleau sand injected by nanosilica and sodium silicate were conserved in atmosphere, water, salt solution and acid solution for 8 different time periods. The shrinkage of the pure gels was measured first. Then, the porosity test by saturation method was adopted to analyze and compare the porosity change in terms of the two different materials, different immersed environments, and different conserving times. The results show that the pure gel of nanosilica is much more stable than the pure gel of silicate sodium in all of the environments from the aspect of shrinkage rate. The same law is followed for the sand-gel mixtures. Nanosilica is more stable when immersed in water, which is a valuable characteristic for grouting. Although nanosilica is less stable when immersed in saline and acid solutions, it is much more stable than silicate sodium.