二氧化碳泡沫法碳化加固软弱土的初探研究

Preliminary Investigation on Reinforcement of Soft Soil Based on the Method of Carbonation by Carbon Dioxide Foams

已有研究表明,活性Mg O固化土经CO2碳化数小时可达到或超过相同掺量水泥固化土28d的强度,碳化形成的镁式碳酸化合物能有效降低天然土的含水率、孔隙率,并显著提高土体强度,但在软土中尤其是黏土中通气具有一定难度。本研究选用十二烷苯磺酸钠作为起泡剂,用CO2泡沫处理Mg O混合土,养护后进行含水率、力学特性和酸碱特性测试。结果表明,含水率随养护时间的增加而降低;无侧限抗压强度随着初始含水率增加而呈现先增大后减小;Mg O掺量越高,强度越大。CO2泡沫固化土的p H值处于10.0~10.87范围内,远低于相应水泥固化土(11.5以上),随养护时间的增加,p H值逐渐下降。但强度增长与预期强度相差甚远,需要对起泡剂和操作工艺上需进行进一步优选。

Studies have demonstrated that the carbonated reactive Mg O-admixed soils could in a few hours reach or exceed 28-d strength of cemented soils with the same cement content. Hydrated magnesium carbonates were the main products of the carbonated reactive Mg O-admixed soils,which could significantly reduce the soil water content and porosity and improve the strength of natural soils. However,its application in soft soils,especially in the clay,is very difficult due to the smaller initial porosity. This study has chosen the dodecane-1-sulfonic acid sodium as a foaming agent,treated the soils by using the CO2 foam and Mg O and carried out experiments of the water content,mechanical properties and acid-base properties after curing. The results show that: the moisture content decreases with the increase of curing time; the unconfined compressive strength of samples would increase and then decrease with the increase of moisture content; the higher the content of reactive Mg O,the greater would be the strength of samples. Moreover,the soil p H of solidified reactive Mg O-admixed soil by CO2 foaming method varies from 10. 0 to10. 87,far lower than that of the corresponding cement-solidified soil( > 11. 5); the soil p H value decreased gradually with the increase of the curing time. However,the increase of the strength is far away from the expected strength,so the foaming agent and operating process need to be further optimized.