Influence of soil type on strength and microstructure of carbonated reactive magnesia-treated soil

Accelerated carbonation of reactive magnesia (MgO)-treated soil is an innovative and sustainable method for improving ground through absorbing CO2. The strength and microstructural properties of various types of carbonated soils at varying initial water contents (w(0)) are explored, and liquid limit (w(L)), a parameter representing soil type, is highlighted in this paper. The strength properties of carbonated soils are investigated by unconfined compression tests. To explain the carbonation mechanism, the microstructural properties are obtained from different experimental tests: X-ray diffraction, scanning electron microscopy, thermogravimetric analysis and mercury intrusion porosimetry. The results indicate that large amounts of CO2 and water are consumed in the carbonation process, which results in the reduction of water content and the formation of carbonation products such as nesquehonite and hydromagnesite/dypingite. The strength of carbonated soils decreases with the increase in w(L) or water content. A simplified equation is proposed for predicting the strength of carbonated soils when both the w(L) and w(0) are given. Silt is easier to absorb CO2 for carbonation than silty clay and clay. Moreover, the pore volume and the quantity of carbonation products decrease with increase in w(L), and the content of CO2 absorbed decreases with increase in w(L) or w(0).