Initial investigation into the carbonation of MgO for soil stabilisation

While Portland cement (PC) is the most widely used binder for soil stabilisation, there are significant environmental impacts associated with its production in terms of high energy consumption and CO2 emission. Hence, the development of new low carbon foot-print alternative cements has been encouraged. In this paper, reactive magnesia (MgO) was used as a soil stabilisation binder and the MgO-stabilised soils were carbonated by gaseous CO2 to improve the mechanical properties of the soil and reduce the CO2 emission. The mechanical and microstructural properties of the carbonated MgO stabilised soils were investigated by using unconfined compressive testing, x-ray diffraction (XRD) and scanning electron microscopy (SEM). The results showed that the strength development rates of carbonated MgO-stabilised soils were much faster than those PC- and MgO-stabilised soils, and the unconfined compressive strength of highly carbonated MgO-stabilised soils was close to that of 28-day ambient cured PC-stabilised soils. The XRD and SEM results indicated that nesquehonite (MgCO3 3H2O) was the main product of the carbonated MgO-stabilised soils and responsible for the significant strength development.