Strength and electrical resistivity characteristic of carbonating reactive MgO-mixed red clay under different water contents

Abstract

As a sustainable green and efficient foundation treatment technology, reactive magnesia (MgO) and carbon dioxide (CO₂) carbonation–stabilization methods are applied innovatively to improve the engineering properties of red clay. The effect of initial water content, carbonation time on the mechanical, electrical and microstructural properties of carbonated solidified MgO-mixed red clay is analyzed systematically through unconfined compressive strength–electrical resistivity synchronous test, X-ray diffraction and scanning electron microscopy test. The test results demonstrated that the stress–strain–resistivity curves of MgO carbonated red clay present good regulation, in which the stress–strain curves first increase sharply and then drop under the loading process, while the resistivity–strain curves display an opposite trend. The unconfined compressive strength (UCS) of carbonated samples, which is affected significantly by the increase in the water content and carbonation time is increasing apparently compared with no-binder parent soil. The process of carbonation exerts a perceptible effect on the relationship of UCS-E₅₀, and the strength gain of carbonated specimens is contacted closely with the uptake amount of CO₂ under the same initial parameters. Compared with carbonation duration, the initial water content has larger influence on the electrical resistivity of carbonated specimens, and the fitting equations combined with the strength and resistivity of carbonated samples were proposed. A series of mineralogical and microscopic tests, including XRD and SEM, demonstrated that nesquehonite and dypingite or hydromagnesite play an important role in improving the strength. The crystalline nesquehonite can make the structure of soil tighter because of the better cementation capacity and reduce effectively the influence of the swell of carbonation process.