Abstract: It has been shown that reactive MgO-stabilized soils carbonated by CO2 after a few hours have almost the same or even more strength of 28-day curing cemented soils. The predominant products of the carbonated reactive MgO-stabilized soils are the hydrated magnesium carbonates, which can significantly reduce the water content and porosity of stabilized soils, and increase the binding strength between soil particles. The sulfate resistance of carbonated reactive MgO-stabilized soils is further studied through laboratory tests. The sodium and magnesium sulfate solutions are selected respectively for soaking the carbonated soil samples and contrasting to cemented soil samples. After soaking different days, the unconfined compressive strength of these samples are measured, and then the microstructure characteristics are analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM) and Mercury intrusion porosimetry (MIP) tests. The results show that the unconfined compressive strength of the MgO-stabilized soils can reach about 5 MPa after the carbonation of 3 hours. It remains almost the same strength and mass after the sulfate attack of 28 days, while the strength of the cemented soil decreases greatly after sulfate attack with its mass significantly increasing, though it increases slightly at the shorter attacking time (7 days). The microstructure analysis reveals that the hydrated magnesium carbonates generated by carbonation and its pore structure do not change significantly after the sulfate attack, thus ensuring its stable strength. Therefore, it can be concluded that the carbonated reactive MgO-stabilized soil has better resistance to the sulfate attack compared to the cemented soil.

Key words: soil stabilization, reactive MgO, carbonation, cemented soil, sulfate