活性MgO碳化固化土的抗硫酸盐侵蚀性研究

既有研究表明，活性MgO固化土经CO2碳化几小时后其强度能达到甚至超过28 d的水泥固化土强度，碳化反应生成镁的碳酸化合物能有效降低固化土的含水率和孔隙率，提高土颗粒胶结能力。通过室内试验进一步研究碳化固化土的抗硫酸盐侵蚀特性。采用硫酸钠溶液、硫酸镁溶液浸泡碳化固化土，对浸泡不同龄期后的碳化固化土进行无侧限抗压强度试验和微观测试（XRD，SEM和MIP），并与硫酸盐侵蚀后的水泥固化土进行试验对比。结果表明：活性MgO固化粉土碳化3 h，试样的无侧限抗压强度可达5 MPa左右，经硫酸盐溶液浸泡28 d后其强度基本保持不变，试样质量变化也不大；而水泥土试样的早期强度（7 d）则有一定增长，随龄期增长，强度大大降低，质量则明显增长。通过对硫酸盐侵蚀前后的碳化土的微观机制分析，发现活性MgO碳化固化土中的镁碳酸化合物的化学成分并未发生明显变化，孔隙结构也未明显改变，从而保证其强度稳定。因此，活性MgO固化粉土碳化后具有比水泥固化土更强的抗硫酸盐侵蚀能力。

Study of resistance to sulfate attack of carbonated reactive MgO-stabilized soils

It has been shown that reactive MgO-stabilized soils carbonated by CO2 after a few hours have almost the same or even more strength of 28-day curing cemented soils. The predominant products of the carbonated reactive MgO-stabilized soils are the hydrated magnesium carbonates, which can significantly reduce the water content and porosity of stabilized soils, and increase the binding strength between soil particles. The sulfate resistance of carbonated reactive MgO-stabilized soils is further studied through laboratory tests. The sodium and magnesium sulfate solutions are selected respectively for soaking the carbonated soil samples and contrasting to cemented soil samples. After soaking different days, the unconfined compressive strength of these samples are measured, and then the microstructure characteristics are analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM) and Mercury intrusion porosimetry (MIP) tests. The results show that the unconfined compressive strength of the MgO-stabilized soils can reach about 5 MPa after the carbonation of 3 hours. It remains almost the same strength and mass after the sulfate attack of 28 days, while the strength of the cemented soil decreases greatly after sulfate attack with its mass significantly increasing, though it increases slightly at the shorter attacking time (7 days). The microstructure analysis reveals that the hydrated magnesium carbonates generated by carbonation and its pore structure do not change significantly after the sulfate attack, thus ensuring its stable strength. Therefore, it can be concluded that the carbonated reactive MgO-stabilized soil has better resistance to the sulfate attack compared to the cemented soil.