Abstract
The study evaluated the effect of four treatment compositions on the plasticity of tropical red soil (Lateritic soil) admixed with Bacillus coagulans (B. coagulans). Samples for Atterberg limits test were prepared using four treatment compositional variables. They include 25% B. coagulans suspension and 75% cementation reagent, (25%B /75%C); 50% B. coagulans suspension and 50% cementation reagent (50% B /50%C); 75% B. coagulans suspension and 25% cementation reagent, (75%B /25% C) with the above three being in equivalent volumes of the corresponding liquid limit(LL) and 50% of the optimum moisture content (OMC) of compaction, to be both B. coagulans suspension and cementation reagent (i.e. 50% OMC B /50%OMC C) of the natural soil. Results showed that the LL for; 25%B /75% C, 50% B /50% C and 75% B /25%C generally increased from 0 up to peak values at 1.8 x 109 cells/ml and then declined at 2.4 x 109 cells/ml. In the case of samples treated with 50% OMC B/50% OMC C, the LL initially decreased from 0 up to 6.0 x 108 cells/ml and thereafter increased significantly. Plastic limit (PL), Plasticity index (PI) and Linear shrinkage (LS), recorded improvement. Regression analysis for the best treatment composition (i.e 75%B /25%C) has regression coefficient of 91.8%. Based on the four treatment compositions considered, 75%B/25%C enhanced the soil workability significantly and is suggested for geotechnical engineering applications such as road pavements that are lightly trafficked.
Highlights
Lateritic soil is a reddish tropical soil found in abundance in Nigeria which in most case is not fit for usage as construction material in its natural form due to high fines content, high water absorption, swelling and shrinkage problems during wetting and drying and so on
The natural soil categorized as A-4(2) soil according to American Association of State Highway and Transportation Officials [23] classification system and SC soil according to Unified Soil Classification System (USCS) [24]
The Plot of calcium carbonate content (CCC) with B. coagulans suspension density is displayed in fig
Summary
Lateritic soil is a reddish tropical soil found in abundance in Nigeria which in most case is not fit for usage as construction material in its natural form due to high fines content, high water absorption, swelling and shrinkage problems during wetting and drying and so on. Many of such soils are deficient for engineering applications and need improvement prior to field application. The bio-cemented columns of sand were broadly analyzed and recorded a decline in permeability and increase in strengths This finding gave rise to microbial-induced calcite precipitation (MICP). MICP is a new sustainable and environmentally friendly soil improvement procedure that makes the use of soil micro- organisms (such as B. coagulans) to precipitate calcite through urea hydrolysis
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