On the rheological, fresh and strength effects of using nano-silica added geopolymer grout for grouting columns

In this article, the influence of nano-silica (NS) added geopolymer-based grout (GBG) mixtures for use in grouting columns was investigated experimentally. For this purpose, the rheological characteristics (shear stress, apparent viscosity, yield stress, plastic viscosity and rheological behaviour) of GBG mixtures obtained with nano-silica (NS) together with fly ash (FA) replacements were measured at a wide range of NS dosages of 0% (only FA for control), 0.5%, 1.0%, 1.5%, 2.0% and 2.5%, and extensive effects of water to binder (w/b) ratios (w/b = 0.50, 0.75, 1.00, 1.25, and 1.50), by dry weight. From a proper and common consistency of water effects (w/b = 1.00), the fresh state properties (mini-slump, Marsh funnel viscometer and bleeding) and unconfined compressive strength (UCS) performance of geopolymer grouting columns were tested. Results of the study indicated that incorporating NS into GBG mixtures had positive effects on the rheological characteristics. The mini-slump and flow time of the Marsh funnel increased slightly with NS dosages up to the rate of 1.5% while increasing the NS proportions led to a reduction of bleeding that was prominent beyond 1.5%NS. Among the treatments of geopolymer mixtures with NS, the highest UCS performance was obtained at the dosage rate of 1.5%NS.