Experimental study on drying-wetting properties of carbonated reactive MgO-stabilized soils

The carbonated curing technology is an innovative ground improvement method, in which the reactive magnesia (MgO) is firstly mixed with the soft soils and then carbon dioxide is injected for carbonation in short time. Laboratory tests are performed to investigate the physical and mechanical properties of carbonated reactive MgO-stabilized soils under drying-wetting cycles. The test results are compared with those of cemented soils. It is shown that the maximum unconfined compressive strength of MgO-stabilized silts can reach 5 MPa after 3 hours carbonation, and that of MgO-stabilized silty clay can only reach 2.6 MPa after 24 hours carbonation. The dry density of carbonated MgO-stabilized soils decreases after drying-wetting cycles, while that of cemented soils has significant variation. Silt samples have better performance after drying-wetting cycles, and the maximum unconfined compressive strength of carbonated silt samples is still able to reach 4 MPa after 6 drying-wetting cycles which is twice that of cemented silts. However, the residual compressive strength of the carbonated silty clay is only 35% after 6 cycles, and it is consistently about 65% for the cemented silty clay, therefore the resistance to drying-wetting cyclic performance is worse than that of silt samples, and the resistance to drying-wetting cyclic performance of carbonated silty clay is worse than cemented silty clay. XRD, SEM and MIP tests reveal that the cumulative volume of pore void of carbonated silt is essentially constant. Thus the carbonated silt samples can still show relatively high strength in the unconfined compressive tests. Whereas, the void ratio of carbonated silty clay increases after cyclic drying-wetting tests and further reduces the density, which is responsible for the significant strength reduction.