氯氧镁水泥固化淤泥力学特性及微观机制

将氯氧镁水泥(MOC)创新性地引入淤泥固化,通过无侧限抗压强度、固化体含水率、扫描电子显微镜(SEM)和X射线能谱测定(EDS)等试验,研究了初始含水率、MgO/MgCl2摩尔比、养护龄期和MgO活性等复杂因素对淤泥固化效能影响及其驱动机制。结果表明:初始含水率越高,试样强度越低,中等含水率时MOC固化淤泥中出现针杆状的3相或5相晶体;随MgO/MgCl2摩尔比升高,试样抗压强度随之增加,水化产物从无定形凝胶逐渐转化为3相、5相和Mg(OH)2晶体;随养护龄期延长,固化淤泥强度总体呈上升趋势,28d前强度增长相对较快,28d后强度趋于稳定;养护后期,MgO/MgCl2摩尔比较高的试样表面易出现泛霜现象;MgO活性提高使得MOC固化淤泥试样含有更多有效活性组分,无侧限抗压强度更高,但MgO活性高低对水化产物演变规律并无显著影响。研究成果可为绿色、低碳MOC基胶凝材料研发及其在淤泥固化等土体加固领域中应用提供理论支撑。

Mechanical properties and micro-mechanisms of magnesium oxychloride cement solidified sludge

Magnesium oxychloride cement(MOC) is innovatively introduced into sludge solidification. The influence of initial water content, molar ratio of MgO/MgCl2, curing age and MgO activity on sludge solidification efficiency and the corresponding driving mechanisms are systematically studied by unconfined compressive strength, water content of solidified matrix, scanning electron microscopy(SEM) and energy dispersive spectrum(EDS). The results show that the higher the initial water content, the lower the strength of solidified samples, and the needle-rod shaped crystals(phase 3 or phase 5) can be clearly observed in MOC solidified sludge with medium water content. The increase in molar ratio of MgO/MgCl2 leads to an improvement in the compressive strength of samples, accompanied by the transformation of hydration products from amorphous gel to phase 3, phase 5 and Mg(OH)2 crystals. The strength of solidified sludge shows a increase trend with the prolongation of curing age, and the strength prior to 28 d increases relatively faster, followed by a stable trend after 28 d. Especially, the surface of specimens with high molar ratio of MgO/MgCl2 is prone to have frost at a longer curing stage. An enhancement in MgO activity produces more reactive components and leads to higher compressive strength of MOC solidified sludge, whereas the activity degree of MgO has no significant effect on the evolution of hydration products. The obtained results can provide a theoretical support for the development of green and low-carbon MOC-based cementitious material and its application in soil reinforcement fields such as sludge solidification.