Experimental study on drying-wetting properties of carbonated reactive MgO-stabilized soils
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摘要: 碳化固化技术是一种利用二氧化碳对搅拌有活性氧化镁的土体进行碳化,以达到快速提高强度的低碳搅拌处理软土的创新技术。通过室内试验研究干湿循环对碳化固化土物理力学特性的影响,并与相同掺量下水泥固化土进行对比。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,粉质黏土碳化24 h试样可达2.6 MPa;干湿循环后碳化固化土的干密度降低,而水泥土干密度基本不变;6次干湿循环后粉土碳化试样的无侧限抗压强度仍然能达到4 MPa以上,为水泥固化粉土强度的2倍,具有较好的抗干湿循环性能;经过6次干湿循环后,粉质黏土碳化试样的残余强度仅为35%,而水泥固化粉质黏土降到65%,表明固化粉质黏土的抗干湿循环性能均较差,且粉质黏土碳化试样的抗干湿循环能力不及水泥固化粉质黏土试样。通过X射线衍射（XRD）、电镜扫描（SEM）及压汞试验（MIP）测试表明干湿循环对粉土碳化试样的累计孔隙影响不大,因此粉土试样仍然具有比较大的密实度来保证试样强度;粉质黏土碳化试样因孔隙增加明显而变得疏松,因此强度显著降低。Abstract: The carbonated curing technology is an innovative ground improvement method, in which the reactive magnesia (MgO) is firstly mixed with the soft soils and then carbon dioxide is injected for carbonation in short time. Laboratory tests are performed to investigate the physical and mechanical properties of carbonated reactive MgO-stabilized soils under drying-wetting cycles. The test results are compared with those of cemented soils. It is shown that the maximum unconfined compressive strength of MgO-stabilized silts can reach 5 MPa after 3 hours carbonation, and that of MgO-stabilized silty clay can only reach 2.6 MPa after 24 hours carbonation. The dry density of carbonated MgO-stabilized soils decreases after drying-wetting cycles, while that of cemented soils has significant variation. Silt samples have better performance after drying-wetting cycles, and the maximum unconfined compressive strength of carbonated silt samples is still able to reach 4 MPa after 6 drying-wetting cycles which is twice that of cemented silts. However, the residual compressive strength of the carbonated silty clay is only 35% after 6 cycles, and it is consistently about 65% for the cemented silty clay, therefore the resistance to drying-wetting cyclic performance is worse than that of silt samples, and the resistance to drying-wetting cyclic performance of carbonated silty clay is worse than cemented silty clay. XRD, SEM and MIP tests reveal that the cumulative volume of pore void of carbonated silt is essentially constant. Thus the carbonated silt samples can still show relatively high strength in the unconfined compressive tests. Whereas, the void ratio of carbonated silty clay increases after cyclic drying-wetting tests and further reduces the density, which is responsible for the significant strength reduction.
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Keywords:
- soil stabilization /
- carbonation /
- drying-wetting cycle /
- cemented soil
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