Development and characterization of eco-and user-friendly binder for grouting and deep mixing via mechanochemical activation of slag/fly ash-based geopolymer

This research uses a mechanochemically activated geopolymer approach to develop and characterize eco- and user-friendly binders for grouting and deep soil mixing. The method involves dry grinding together the raw materials (fly ash and slag) and alkali activators (sodium hydroxide or sodium silicate) in a ball mill for two hours, after which water is the only additive required to initiate the geopolymerization reaction. The resulting binder was compared to conventionally activated and one-part geopolymer binder for evaluation purposes. The effects of slag/fly ash ratios and the molarity of sodium hydroxide on geopolymer grout mixtures were also investigated. A series of tests were performed, including rheological behavior, fresh properties, mechanical characteristics, and microstructure analysis. The results showed that the mechanochemical activation technique reduced the rheological characteristics and fresh properties of geopolymer grout compared to the conventional activation process. However, the mechanical properties of the mechanochemically activated geopolymer (MG) grout were higher than that of the conventionally activated geopolymer (CG) and one-part geopolymer (OPG) grout. In addition, the increase in molar concentration and slag content considerably increased the rheological and mechanical properties, whereas the fresh properties were dramatically reduced. The research also investigated the Mechanical and durability properties of deep soil mixing (DSM) specimens exposed to magnesium sulfate, sulfuric acid, and seawater solutions for 60 and 120 days. The results showed that the DSM samples stabilized with mechanochemically activated geopolymer (MAG) had a denser microstructure with a well-connected gel-like network, whereas conventionally activated geopolymer (CAG)-stabilized soil exhibited a loose microstructure with unreacted particles. MAG-stabilized soil showed better resistance to chemical attack from magnesium sulfate, sulfuric acid, and seawater, with less mass change and better residual unconfined compressive strength values. Samples with 75% slag replacement showed the highest resistance to chemical attack compared to other DSM samples. These findings suggest that MAG-activated geopolymer stabilization can be a more effective and durable method for stabilizing soil. Key Words: Grouting, Deep Soil Mixing, Mechanochemical Activation, Geopolymer, Rheological, Strength, Durability, Chemical Attack