Engineering Properties of Carbonated Reactive Magnesia-stabilized Silt Under Different Activity Index

Engineering properties of soft soils can gain great improvement through the addition of reactive magnesia (MgO) and further carbonation of substantial gaseous CO2 absorbed. The paper studies the influence of MgO activity index on engineering properties of the carbonated silt with different water-MgO ratio. The engineering properties are investigated mainly through unconfined compression tests, and then the strength development are explained by the scanning electron microscopy (SEM). The results demonstrate that the mechanical properties of carbonated MgO-stabilized soils were greatly influenced by MgO activity index and water-MgO ratio, and the unconfined compressive strength of reactive MgO-stabilized soil has increased obviously after CO2 carbonation. With increasing MgO activity index and reducing water-MgO ratio, the unconfined compressive strength increased, and the failure mode of carbonated specimens approximately changes from elastic-plastic to brittleness as well as their failure strain mainly ranges between 0.5% and 2.3%. The deformation modulus of carbonated silt generally increases with increasing unconfined compressive strength, and the ratio of the deformation modulus to unconfined compressive strength is about 35 to 150. A simplified equation with combining MgO activity index and water-MgO ratio is proposed for accurately predicting the unconfined compressive strength of carbonated MgO-stabilized soils. Moreover, the microstructural characteristics explain the strength gain of carbonated MgO-stabilized soils.