活性MgO碱性激发粒化高炉矿渣固化黏土的抗硫酸盐侵蚀试验研究

Study of durability of reactive magnesia-activated ground granulated blast-furnace slag stabilized soil attacked by sulfate sodium solution

通过系列室内试验,研究了硫酸盐长期浸泡环境下GGBS-Mg O固化黏土的物理和力学性质及微观特征变化规律,并与水泥固化黏土进行对比,揭示了GGBS-Mg O固化黏土抵抗硫酸盐侵蚀的机制。与水泥固化黏土相比,硫酸盐浸泡条件下GGBS-Mg O固化黏土表面完整度较好;质量变化率在浸泡120 d时仅为水泥固化黏土的0.25倍;固化黏土体p H略小于同期水泥固化黏土;浸泡初期GGBS-Mg O固化黏土强度增长达20%,同周期时无侧限抗压强度较水泥固化黏土高15%~80%。X射线衍射试验(XRD)表明,硫酸盐侵蚀下GGBS-Mg O固化黏土中水化硅酸钙(C-S-H凝胶)的峰值高于水泥固化黏土,而钙矾石(AFt)的XRD图谱峰值明显低于水泥固化黏土。电镜扫描试验结果表明,两种固化黏土中钙矾石形态明显不同:钙矾石在水泥固化黏土中以团聚型晶体存在,可具较强膨胀性,而在GGBS-Mg O固化黏土中则以细短形态分布于颗粒间,可有效填充试样孔隙,使其具备良好的抗硫酸盐侵蚀能力。

This study investigates the physico-mechanical properties, as well as the microstructural characteristics of the reactive magnesia(Mg O)-activated ground granulated blast-furnace slag(GGBS) stabilized kaolin clay via a series of Na2SO4 solution soaking durability tests. For the purpose of comparison, the cement stabilized kaolin clay is selected as a control sample. The results show that the mass loss of GGBS-Mg O stabilized soil is 0.25 times lower than that of PC stabilized soil soaked for 120 days. The unconfined compression strength(qu) of GGBS-Mg O stabilized soil has a significant increase of as much as 20% at the early stage. Furthermore, qu of GGBS-Mg O stabilized soil is 15% to 80% higher than that of PC stabilized soil. The results of X-ray diffraction analysis show that the GGBS-Mg O stabilized soil has higher peak of calcium silicate hydrate(C-S-H) and lower peak of AFt relative to the PC stabilized soil. The scanning electron microscopy test shows the morphological characteristics of ettringite(AFt) in these two types of stabilized soils are different. For the PC stabilized soil, the AFt exists in the form of swelling aggregates. Unlike PC stabilized soil, the AFt of GGBS-Mg O stabilized soil is in the fine small form and exists between the soil particles, which can promote the filling of large pores, leading to a higher resistance to the sulfate attack.