活性MgO碳化固化土的渗透特性研究

Permeability properties of carbonated reactive MgO-stabilized soils

碳化固化法是一种低碳搅拌处理软土的创新技术,碳化反应生成的产物能有效降低固化土的孔隙率。在已有研究的基础上,着重研究碳化土的渗透特性,以利于其工程应用。采用室内渗透试验,系统研究了活性MgO掺量、碳化时间、初始含水率和CO2通气压力对MgO碳化粉土和碳化粉质黏土渗透系数的影响规律,并与相同固化剂掺量、相同初始含水率下水泥固化土的渗透系数进行了对比。结果表明：活性MgO碳化土的渗透系数随MgO掺量的增加而降低,与相同掺量下水泥固化土的渗透系数处于同一数量级;MgO碳化粉土的渗透系数明显大于碳化粉质黏土的渗透系数;当MgO碳化粉土和粉质黏土碳化6.0 h时,相应的渗透系数达到最小（10-6）;通气压力对MgO碳化土的渗透系数影响不大,在通气压力为200 k Pa时渗透系数较小。因此,活性MgO碳化土具有与水泥固化土相近的抗渗性能,有良好的推广应用前景。

The carbonation method of reactive MgO-stabilized soils is an innovative technology for the treatment of soft soils with low carbon. The products produced by carbonation reaction can effectively reduce the porosity of solidified soils. Based on the existing researches, the permeability of reactive magnesia（MgO）-carbonated soils is highlighted for its application in engineering. Through the laboratory permeability tests, the influences of reactive MgO content, carbonation time, initial water content and CO2 ventilation pressure on the permeability coefficient of carbonated silt and carbonated silty clay are systematically studied. In addition, the permeability coefficients of Portland cement（PC）-treated soils is used for comparison under the same conditions of curing agent content and initial water content. The investigation results indicate that the permeability coefficient of reactive MgO-carbonated soils reduces with the increasing MgO content, and it is in the same order of magnitude compared with PC-treated soils with the same curing agent content. The permeability coefficient of carbonated silt is obviously larger than that of carbonated silty clay. When both the reactive MgO-stabilized silt and silty clay are carbonated for 6.0 hours, the corresponding permeability coefficient can reach the minimum（10-6）. The ventilation pressure has little effect on the permeability coefficient of reactive MgO-carbonated soils, and the permeability coefficient is slightly smaller when the ventilation pressure is 200 k Pa. Therefore, the reactive MgO-carbonated soil has a similar impermeability to the cement-treated one, and has a good prospect of popularization and application.