Experimental investigation on metakaolin/coal fly ash-based porous geopolymer grouting material for geotechnical applications

This research investigates the development of a porous geopolymer cement grout for soil grouting applications, aiming to reduce carbon emissions associated with Portland cement while maintaining critical performance characteristics such as strength and permeability. Class F fly ash and metakaolin were used as aluminosilicate precursors, activated by sodium silicate and sodium hydroxide solutions. The addition of hydrogen peroxide served as a foaming agent to introduce porosity. Compressive strength and porosity were evaluated, with results showing that metakaolin significantly increased compressive strength due to its smaller particle size and higher reactivity. A higher molarity of sodium silicate enhanced strength by reducing the water-to-solid ratio, creating a denser matrix. In contrast, increasing hydrogen peroxide content raised porosity but reduced compressive strength by generating gas bubbles. X-ray diffraction (XRD) analysis revealed the ongoing formation of hydration products and a growing amorphous structure in the geopolymer matrix, contributing to strength development over time. The study concludes that the geopolymer grout can be optimized for a wide range of soil stabilization applications by adjusting material composition, foaming agent concentration, and activator molarity, offering an environmentally sustainable alternative to traditional cement grouts.