活性氧化镁碳化加固粉土微观机理研究

基于活性MgO-CO2碳化固化法，开展了不同活性MgO掺量、碳化时间和初始含水率条件下的碳化粉土的无侧限抗压试验、X-射线衍射(XRD)、扫描电镜(SEM)和压汞试验(MIP)等，以通过无侧限抗压强度、化学成分、结构形貌和微观孔隙等特征来揭示碳化固化粉土的微观机理，最后提出活性MgO碳化固化粉土微观机理模型。结果表明：活性MgO碳化固化粉土的无侧限抗压强度在12h内随MgO掺量和碳化时间增加而增加，随初始含水率增加而降低|碳化后含水率显著降低，且强度与含水率间呈很好的线性负相关关系。碳化生成的水化镁式碳酸盐，包括棱柱状水菱镁石、薄片状球菱镁石/水碳镁石和纤维碳镁石，这些碳化产物对应的XRD峰强随MgO掺量和碳化时间增加而增加，随初始含水率增加而降低|存在最优MgO掺量和初始含水率，使碳化土孔隙体积最小。碳化土无侧限抗压强度与水菱镁石晶体对应的XRD峰强呈正相关关系。水菱镁石的生成促进了强度增长，与其他碳化产物共同促进土体孔隙减小。

Research on micro-mechanism of carbonated reactive MgO-stabilized silt

Based on the reactive MgO-CO2 carbonation method, several tests were conducted on the carbonated reactive MgO-stabilized silts with different reactive MgO content, carbonation time and initial water content. Based on the unconfined compression test, X-ray diffraction (XRD), scanning electron microscopy (SEM) and mercury intrusion porosimetry (MIP), the micro-mechanism of carbonated silts were explored by analyzing the unconfined compressive strength, chemical compositions, structural morphology and the microscopic pores. The micro-mechanism model of carbonated MgO-stabilized silt was put forward. The research results indicate that the unconfined compressive strength of the carbonated reactive MgO-stabilized silt increases with the reactive MgO content and carbonation time (within 12 hours) whereas decreases with the initial water content. The water content reduces significantly after carbonation and there exists a very good linear negative correlation relationship between the strength and the water content. There are many hydrated magnesium carbonates in the carbonated silt, including prismatic nesquehonite, flaky dypingite/ hydromagnesite and artinite, whose corresponding XRD peaks increase with the reactive MgO content and carbonation time while they decrease with the initial water content. The optimal conditions of reactive MgO content and initial water content exist, thus the pore volume of carbonated silt can be minimum. The unconfined compressive strength of the carbonated silt is linearly related to the corresponding XRD peaks of nesquehonite crystal. The formation of nesquehonite promotes the growth of strength and reduces the pores together with other carbonation products.