Mo Yixin, Yue Songlin, Zhou Qizhen, Liu Xiao
College of Defence Engineering, Army Engineering University of PLA, Nanjing 210007, China.
Materials (Basel). 2021 Sep 7;14(18):5140. doi: 10.3390/ma14185140.
Recently, microbially induced carbonate precipitation (MICP) has been studied as an alternative for the improvement of sand-clay mixtures. However, the cementing uniformity of MICP-treated sand-clay mixtures cannot be guaranteed. In this present study, enzymatic-induced carbonate precipitation (EICP) was used to deal with it. The ions used in kaolin clay was predicted to affect the production rate for calcium carbonate (CaCO), which was studied using the calcification test. The solidification test was conducted using two different methods (the premixing method and the diffusion method). The permeability, unconfined compressive strength and the content of CaCO of treated samples were obtained to evaluate the solidification effect of the EICP method. Moreover, in EICP treatment, the particle aggregation decreased the liquid limit, but the addition of solution increased it. Therefore, there were contrary effects to the soil consistency. In this study, the two types of liquid limits of treated samples were measured with deionized water and 2M-NaCl brine, respectively. The results show that the AlO, NaCl and MgCl in the kaolin clay had a slight impact on the production rate for CaCO, while FeCl significantly inhibited it. The EICP method can improve sand-clay mixtures and decrease their permeability. Different from MICP, the EICP method can guarantee the uniformity of treated samples. Moreover, the liquid limit of the sample treated with the premixing method decreased, while that of the sample treated with the diffusion method increased firstly and then decreased with the increasing treatment cycles. Different from the deionized water, the pore-fluid chemistry had a larger effect on the liquid limit with 2M-NaCl brine.
最近，微生物诱导碳酸盐沉淀（MICP）已被作为改善砂-粘土混合物的一种替代方法进行研究。然而，经MICP处理的砂-粘土混合物的胶结均匀性无法得到保证。在本研究中，采用酶促诱导碳酸盐沉淀（EICP）来处理这一问题。预测高岭土中使用的离子会影响碳酸钙（CaCO₃）的生成速率，并通过钙化试验对此进行了研究。采用两种不同方法（预混合法和扩散法）进行固化试验。获取处理后样品的渗透率、无侧限抗压强度和CaCO₃含量，以评估EICP方法的固化效果。此外，在EICP处理中，颗粒聚集降低了液限，但溶液的添加使其升高。因此，对土壤稠度有相反的影响。在本研究中，分别用去离子水和2M-NaCl盐水测量了处理后样品的两种液限。结果表明，高岭土中的Al₂O₃、NaCl和MgCl₂对CaCO₃的生成速率有轻微影响，而FeCl₃则显著抑制了该速率。EICP方法可以改善砂-粘土混合物并降低其渗透率。与MICP不同，EICP方法可以保证处理后样品的均匀性。此外，采用预混合法处理的样品液限降低，而采用扩散法处理的样品液限随处理循环次数的增加先升高后降低。与去离子水不同，孔隙流体化学对2M-NaCl盐水的液限影响更大。
