Abstract: In this study, reactive magnesia (MgO) is used as a binder to carbonate and stabilise silty clay. The changes of unconfined compressive strength, soil pH, carbonation products, and microstructure of the silty clay carbonated and stabilized by reactive MgO are studied at different carbonation time and initial water contents through the experiments of unconfined compression, pH, X-ray diffraction, mercury intrusion porosimetry and scanning electron microscope, respectively. The micromodel of carbonation reaction of silty clay is proposed according to the intrinsic relationships between the strength of carbonated soil and contents of carbonation products as well as the cumulative pore volume. The results show that with the increase of the carbonation time or the decrease of the initial water content of carbonated samples, the carbonation products increase, and the strength of reactive MgO stabilized soil gradually increases with the decrease of cumulative pore volume. Moreover, the pH values of reactive MgO-stabilized soil decreased with the increase of the carbonation time, whereas the initial water contents show no obvious changes. Finally, the micromodel of carbonation reaction of silty clay is established, and the highest strength of reactive MgO-stabilized silty clay is determined after about 6 hours of carbonation.

Key words: reactive magnesia, silty clay, carbonation, soil stabilisation, microstructural mechanism