Analysis of strength development in cement-treated soils under different curing conditions through microstructural and chemical investigations

This study investigated the strength development of cement-treated soils by considering not only the interactions among cement hydration and pozzolanic reaction, but also the carbonation process. Indeed, the chemical and microstructural changes in cement-treated soils are due to carbonation combined with previous reactions and no studies took into account all processes at the same time. Three soil specimen types (specifically, sand, sand-loam, and sand-bentonite mixtures) were cured under sealed and drying conditions and their unconfined compressive strength, microstructural and chemical properties subsequently measured over time. Under drying conditions, behaviors varied with soil mineralogy. The compressive strength of all mixtures significantly increased with decreasing total micropore induced by carbonation and suction effects. However, in the sand-clay mixture under long-term drying, the compressive strength remained constant or slightly decreased after 28 days, correlating with the increase in large capillary pore caused by shrinkage of bentonite and C-S-H carbonation. These results revealed that carbonation could have both positive and negative impacts on strength development of cement-treated soils.