Abstract

The strength of sandy soil can be improved via enzyme-induced calcium carbonate (CaCO₃) precipitation (EICP). This method is a sustainable and environmentally friendly soil improvement technique that forms calcium carbonate between and around the soil particles. The formation of CaCO₃ is achieved through the hydrolysis of urea that is catalyzed by free enzyme urease. This paper is divided into two parts. The first part explains the test-tube tests that were conducted to determine the amount and efficiency of CaCO₃ precipitation at different concentrations of the cementation reagent (CCR). The second part describes the effects of multiple treatment cycles on the unconfined compressive strength (UCS) of EICP-treated soil. The soil samples were mixed with the EICP solution and compacted into PVC moulds. It was then followed by cycles of treatment with the EICP solution via surface percolation. The effectiveness of the bio-cementation was determined through a series of UCS tests. The results revealed that the UCS increased with higher CCR and more treatment cycles. The increase in UCS was also attributed to higher amounts of CaCO₃ precipitated within the soil matrix. The highest UCS value of 1712 kPa was obtained at 1 M after the 3rd cycle of treatment with 8.21% CaCO₃content. In conclusion, a higher number of treatment cycles demonstrated that increased deposition of CaCO₃ precipitates increases the bonding effects and strength of the treated soil. Successful use of EICP in soil improvement will help in reducing sustainability concerns related to the production of conventional stabilizers such as cement.

Graphic abstract

中文翻译：

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多个处理周期对生物胶结砂土强度和微观结构的影响

摘要

沙土的强度可以通过酶诱导的碳酸钙（CaCO ₃）沉淀（EICP）来提高。该方法是一种可持续且环保的土壤改良技术，可在土壤颗粒之间和周围形成碳酸钙。CaCO ₃的形成是通过尿素的水解来实现的，尿素的水解是由游离酶脲酶催化的。本文分为两部分。第一部分说明了用于确定CaCO ₃的数量和效率的试管测试在不同浓度的胶结剂（CCR）中发生沉淀。第二部分描述了多个处理周期对EICP处理的土壤的无侧限抗压强度（UCS）的影响。将土壤样品与EICP溶液混合并压制成PVC模具。然后通过表面渗滤用EICP溶液处理循环。通过一系列的UCS测试确定了生物固井的有效性。结果表明，UCS越高，CCR越高，治疗周期越长。UCS的增加还归因于土壤基质中沉淀的CaCO ₃量增加。在第三个周期用8.21％CaCO ₃处理后的1 M处，获得的UCS最高值为1712 kPa。内容。总之，更高数量的处理周期表明，增加的CaCO ₃沉淀物沉积会增加粘结效果和被处理土壤的强度。在土壤改良中成功使用EICP将有助于减少与生产水泥等常规稳定剂有关的可持续性问题。

图形摘要