Plasticity characteristics of lateritic soil treated with Sporosarcina pasteurii in microbial-induced calcite precipitation application

Abstract

The plasticity characteristics of lateritic soil with varying Sporosarcina pasteurii (S. pasteurii) suspension density and compositional variables were evaluated in microbial-induced calcite precipitation (MICP) application. The liquid limit value of the natural lateritic soil was used to prepare samples with three mix proportions of the bacteria and cementation reagent (i.e., 25% bacteria-75% cementation reagent, 50% bacteria-50% cementation reagent and 75% bacteria-25% cementation reagent). The S. pasteurii suspension densities used to trigger the MICP process are 0, 0.5, 2.0, 4.0, 6.0 and 8.0 McFarland standards (i.e., 0, 1.50 × 10 8 , 6.0 × 10 8 , 1.20 × 10 9 , 1.80 × 10 9 and 2.40 × 10 9 cells/ml, respectively). Tests carried out on the treated specimens include Atterberg limits and linear shrinkage as well as calcite content using the acid wash method. Results obtained showed a general decrease in the Atterberg limit values with higher S. pasteurii suspension density. The best improvement of plasticity index was achieved for lateritic soil prepared with 75% S. pasteurii and 25% cementation reagent at S. pasteurii suspension density of 2.40 × 10 9 cells/ml with a corresponding peak 6.0% calcite content. Also, a maximum 4% contaminant concentration of a synthetic leachate produced the best S. pasteurii growth pattern.

Review of the use of microorganisms in geotechnical engineering applications

“…This finding was contradicted by Chittoori [138], who reported an increase in both the liquid limit and plasticity index of two clay soils and recorded a substantial reduction in the one-dimensional swell strain after bacterial treatment, with corresponding calcite content of 1.60% and 0.90%. Similarly, studies conducted by Osinubi [139] on lateritic soil after varying the ratio of bacteria to cementation reagent showed that an optimal improvement of plasticity index was achieved for specimens prepared with 75% S. pasteurii and 25% cementation reagent at S. pasteurii suspension density of 2.40 × 10 9 cells/ml, with a peak calcite content of 6.0%. This was due to the higher suspension density of S. pasteurii that were available to maximally hydrolyze the urea within the cementation reagent.…”

“…A microorganism can be used for remediation of contaminants if it possesses any of the following characteristics: the ability to utilize, transform, degrade, or grow in the presence of the contaminants, thus toxicity testing is essential, as reported in Ref. [139]. Note that some of these contaminants are essential for cell growth, although they may be toxic at high concentrations due to serious health-related issues.…”

Feasibility study for slope soil stabilization by microbial induced carbonate precipitation (MICP) using indigenous bacteria isolated from cold subarctic region

“…Also, the free passage of microorganisms through the limited pore-throat size remains a challenge in treating the very fine soils using MICP [14]. Recently, researchers have started to focus on assessing the performance of MICP in residual soils that consist fine to coarse grains distributed naturally [14][15][16]. However, only a very limited MICP studies on residual soils have been reported in the literature to the date, providing insufficient information on their mechanical responses.…”

Micro-mechanical performance evaluation of expansive soil biotreated with indigenous bacteria using MICP method

“…The swell pressure has been reduced up to 41 kPa for natural soil and 15 kPa for artificial soil. The MICP treatment procures the calcite content, which creates the bond between the soil grains and the formation of the biofilm also increased the barrier between water and clay particles 53 , 54 . And for the artificial soil BC-1 + 30%BA, BC-2 + 30%BA and BC-3 + 30%BA, the swell pressure has been reduced to 48 kPa, 43 kPa, and 39 kPa %, respectively.…”