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Mg O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Mg O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Mg O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0.1～1.0μm的孔隙减少,1～30μm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-thawdurability of carbonated reactive magnesia（ M g O）-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 M g O-stabilized silts can reach 5 M Pa after carbonated 3 h,and those of M g O-stabilized silty clay can reach 4. 5 M Pa after 24 h carbonation. The density and dry density almost remain constant during the cyclic freeze-thawtests. The UCS and E50 of carbonated reactive M g O-stabilized soils and cemented soils exhibit similar trends that slightly decrease first,then gradually increase. The UCS of carbonated reactive M g O-stabilizes soils reduced from about 5M Pa to about 4. 5 M Pa after 6 freeze-thawcycles,and that of cemented soil reduces from about 1. 6M Pa to about 1. 4 M Pa after 4 freeze-thawcycles,they both have good resistance behaviors to freeze-thawcycles. 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-thawtests. However,pores of 0. 1 to 1. 0 μm reduce,pores of 1 to 30μm increase,leading to the cumulative increase in porosity. That is why the UCS slightly reduces.