Clay and Microsilica Additives’ Effect on the Properties and Structure of Injectable Cement–Clay Mortars for Soil Consolidation

The potential of clay as a replacement for Portland cement in the manufacture of injection cement–clay mortars (ICCMs) for soil stabilization is examined in this investigation. The objective of this study is to produce environmentally friendly injection-molded mortars for soil stabilization based on Portland cement (PC) and clay (C). Experimental ICCMs with C contents ranging from 0% to 50% without the addition of microsilica (MS) and ICCMs with C contents ranging from 0% to 50% and 2% MS were produced. The evaluation included the density, water segregation, and cone spread diameter of fresh ICCMs, alongside the density, flexural strength, and compressive strength of hardened ICCMs. The findings indicated that as C content rose from 0% to 50%, fresh mortars experienced a decrease in density, flowability, and water segregation. Hardened mortars exhibited reduced density, compressive strength, and flexural strength as C content increased. Modifying mortars with MS has a positive effect on their strength properties. The reduction in flexural and compressive strength for mortars with 50% C was 54.2% and 60.1%, respectively, while for similar mortars with 2% MS, the reduction in strength was 47.9% and 51.8%, respectively. ICCM soil stabilization compositions modified with MS are the most effective in comparison with similar compositions without MS and have a homogeneous structure with pores, microcracks, and hydration reaction product zones. The optimal ratios of raw components for the production of ICCMs for soil stabilization were determined: a water–solid ratio of 0.6, PC content from 90% to 50%, C content from 10% to 50%, and an MS content of 2% of the dry component weight. This research contributes to sustainable development by reducing CO2 emissions per 1 m3 of mixture production by up to 47.8% and by using raw materials rationally.