Influences of Activity Index on Mechanical and Microstructural Characteristics of Carbonated Reactive Magnesia-Admixed Silty Soil

摘要

Carbonated reactive magnesia (MgO)-admixed soil is employed for stabilizing soft soil through absorbing gaseous C0_2, which is an innovative and sustainable technique recently developed in the realm of ground improvement. With this in view, a systematic study that targets the influence of the MgO activity index (c_A) on mechanical and microstructural characteristics of carbonated silty soil with different ratios of initial water content to MgO content (represented as w_0/c) is initiated in this paper. In this context, the mechanical properties are investigated through unconftned compression tests, and the microstructural properties are obtained from X-ray diffraction, scanning electron microscopy, thermogravimetry, and mercury intrusion porosimetry analyses. The results demonstrate that c_A and w_0/c are the two crucial factors controlling the mechanical and microstructural characteristics of carbonated MgO-admixed soils. A simplified equation with combination of c_A and w_0/c is proposed for accurately predicting the unconftned compressive strength of carbonated MgO-admixed soils. The analyses of microstructural characteristics indicate that dypingite or hydromagnesite and plentiful crystalline nesquehonite play an important role in reducing the pore volume, and the latter is the primary micromechanistic reason for the strength gain of the carbonated MgO-admixed soils.