Effects of drying-wetting cycles on engineering properties of kaolin clay stabilized by MgO-bicarbonate-GGBS ternary binder

Abstract Carbonating reactive magnesia (MgO) by using sodium bicarbonate (as a carrier of CO 2 ) (i.e. MgO + NaHCO 3 ) is a promising method in stabilizing soils and reducing carbon emissions. However, the effect of drying-wetting (D-W) cycles on the engineering performance of such stabilized soils remains poorly investigated, which poses a key barrier to their engineering application. To enhance the durability against D-W cycles, ground granulated blast-furnace slag (GGBS) was introduced into the MgO-bicarbonate stabilization system. This study systematically compared the D-W cycle resistance of soils before and after GGBS addition through apparent performance, mass and volume change, unconfined compressive strength (UCS), pH, and microscopic characteristics. The results demonstrated that after D-W cycling, soil treated with MgO and a bicarbonate (NH 4 HCO 3 or NaHCO 3 ) exhibited a stabilized strength in the range of 0.62–0.77 MPa. In contrast, incorporating GGBS effectively improved the strength, with values increasing to 1.01–1.15 MPa and 0.83–1.02 MPa for the NH 4 HCO 3 and NaHCO 3 mixtures, respectively. This enhancement underscores the important role of GGBS in substantially boosting the D-W cycle resistance of the MgO-bicarbonate stabilized soil. Microscopic analysis revealed that the cementation by hydrated magnesium carbonates contributed to strength retention. Moreover, the precipitation of calcium silicate hydrate (CSH) and ettringite from activated GGBS provided essential pore-filling and reinforcement. Thus, by incorporating GGBS, this study develops a novel ternary binder system that significantly enhances durability, offering a practical and sustainable strategy for soil stabilization in seasonal wet-dry regions.