活性MgO碳化固化土的冻融循环特性试验研究
Experimental study on freeze-thaw properties of carbonated reactive MgO-stabilized soils

采用室内三轴碳化装置研究了活性MgO碳化固化土的冻融耐久性能,对冻融循环作用下碳化固化土的无侧限抗压强度等进行了测试分析,并与水泥固化土进行了试验比较.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,粉质黏土碳化24 h试样可达4.5 MPa左右;冻融循环作用下,碳化试样和水泥土试样的密度和干密度基本不变;碳化试样与水泥土试样在冻融循环中的无侧限抗压强度和E50表现出类似的变化趋势,即先略有降低,后又逐渐提高.碳化固化土经6次冻融循环后,其强度由5 MPa左右降低到4.5 MPa左右,而水泥土试样经4次冻融循环后其强度由1.6 MPa降低到1.4 MPa左右,二者均具有较好的抗冻融性能.微观测试分析表明, 活性MgO碳化固化土生成的镁碳酸化合物经冻融循环后没有发生明显变化,但试样内部0.1~1.0 μm的孔隙减少,1~30 μm的孔隙增加,累计孔隙体积略有增加,这也是导致强度略有降低的原因.
Laboratory unconfined compressive strength(UCS)tests were performed to investigate the freeze-thaw durability of carbonated reactive magnesia(MgO)-stabilized soils carbonated by triaxial carbonation device. The test results were then compared with those of cemented soils. It is found that the maximum UCS of MgO-stabilized silts can reach 5 MPa after carbonated 3 h, and those of MgO-stabilized silty clay can reach 4.5 MPa after 24 h carbonation. The density and dry density almost remain constant during the cyclic freeze-thaw tests. The UCS and E50 of carbonated reactive MgO-stabilized soils and cemented soils exhibit similar trends that slightly decrease first, then gradually increase. The UCS of carbonated reactive MgO-stabilizes soils reduced from about 5 MPa to about 4.5 MPa after 6 freeze-thaw cycles, and that of cemented soil reduces from about 1.6 MPa to about 1.4 MPa after 4 freeze-thaw cycles, they both have good resistance behaviors to freeze-thaw cycles. Based on microscopic mechanism analysis on mineral composition and pore structure, it shows that hydrated magnesium carbonates generated by carbonation will not change significantly after cyclic freeze-thaw tests. However, pores of 0.1 to 1.0 μm reduce, pores of 1 to 30 μm increase, leading to the cumulative increase in porosity. That is why the UCS slightly reduces