A Laboratory Investigation on Utilization of Alkali-Activated By-Products in Deep Soil Mixing in Silty Sands

Cement is one of the primary construction materials in ground improvement applications that employ the binder stabilization method. Due to the high carbon dioxide emissions in its production, evaluating environmentally friendly alternative binder materials is a popular research topic. Industrial by-products such as fly ash (FA) and ground granulated blast-furnace slag (GGBS) are alternatives to traditional cement, especially in deep soil mixing (DSM) applications, and can enhance sustainability in construction projects. Since these materials are not active when used alone, alkali activation is proposed to modify them as binding agents in ground improvement projects. This study presents the outcomes of a primary laboratory test phase for on-site applications. FA and GGBS precursors supplied by local plants, mixed with soil and activator solutions in applicable ratios, and samples were prepared for laboratory tests. Unconfined compression tests were applied with strain measurements after several curing durations, between 1 and 54 weeks. Average compression strength and modulus of elasticity values were recorded at approximately 12.3 MPa and 11.7 GPa, respectively, in samples with an average dosage. An empirical correlation between the strength and stiffness modulus was found. Strength and stiffness values were comparable to traditional materials, indicating the potential of these industrial by-products when activated under alkali conditions. The carbon footprints of cement and alkali-activated by-products were compared based on calculated CO₂-eq emissions.