On the rheology of using geopolymer for grouting: A comparative study with cement-based grout included fly ash and cold bonded fly ash

Abstract

A friendly novel material called geopolymer has recently presented some promising uses for enhancement of weak ground through grouting alternative to Portland cement especially for avoiding from large CO2 emissions during cement production. However, research using the geopolymer technology is still insufficient for grouting specifically concerning with rheology. This paper investigates the rheological properties (shear stress, apparent viscosity, shear rate, yield stress, plastic viscosity) of geopolymer grout in comparison with the cement-based grouts included fly ash and cold bonded fly ash (i.e., geopolymer aggregate) at various dosage rates (0%–100%) and water/binder ratios (0.75–1.5). Some alkaline activator solutions (sodium hydroxide, sodium silicate) and some precursor of aluminosilicate sources (fly ash, silica fume) are used for obtaining the geopolymer grout. Rheometer tests are performed for the grout rheology. It is found from the experimental work that most of the grout mixtures lead to dilatant behavior similar to the one of native cement, while some geopolymer grouts result in the pseudoplastic and Bingham behaviors. All rheological responses of grouts decrease with increased water/binder ratios. While the inclusions of fly ash and geopolymer aggregate bring about minor changes in the rheological properties, the geopolymer grouts mostly result in the magnitudes more pronounced. The grout rheology becomes more close to the ones of native cement by the proportions 30%–40% of fly ash and geopolymer aggregate, and using the geopolymer grout in the combinations with 30%–60% silica fume. The plastic viscosity versus yield stress produces moderate correlations for the grouts with fly ash, but strong correlations for the geopolymer grouts and the grouts with geopolymer aggregate. The study indicates that the geopolymer comparatively attempted with fly ash and geopolymer aggregate could offer many choices for experimenters in practice for feasible grouting compared to native cement.