Evaluation of the Effectiveness of a Soil Treatment Using Calcium Carbonate Precipitation from Cultivated and Lyophilized Bacteria in Soil’s Compaction Water

Abstract

Microbial-induced carbonate precipitation (MICP) is a bio-inspired solution where bacteria metabolize urea to precipitate. This carbonate acts as a bio-cement that bonds soil particles. The existing framework has focused mainly on applying MICP through infiltration of liquid bacterial solutions in existing soil deposits. However, this technique is inefficient in soils with high fines content and low hydraulic conductivity, and thus few studies have focused on the use of MICP in fine soils. The main objective of this study was to evaluate the effect of MICP applied to compaction water in soils containing expansive clays and sandy silts. This approach searches for a better distribution of bacteria, nutrients, and calcium sources and is easy to apply if associated with a compaction process. In soils with expansive minerals, the effect of MICP in swelling potential was explored at laboratory and field scales. In sandy silts, the evolution of the stiffness and strength were studied at the laboratory scale. The treatment at the laboratory scale reduced the swelling potential; nevertheless, no significant effect of MICP was found in the field test. In sandy silts, the strength and stiffness increased under unsaturated conditions; however, subsequent saturation dissolved the cementation and the improvement vanished.

Simultaneous Biocementation and Compaction of a Soil to Avoid the Breakage of Cementitious Structures during the Execution of Earthwork Constructions

“…It should be noted that optical microscopy was applied very scarcely in previous studies concerning MICP [25][26][27][28][29][30]. Thus, the present study shows that this technique can be complementary to SEM (Figures 6-8).…”

“…Figure 8a shows the micrograph obtained by the SEM and Figure 8b shows the image obtained by the optical microscopy. It should be noted that optical microscopy was applied very scarcely in previous studies concerning MICP [25][26][27][28][29][30]. Thus, the present study shows that this technique can be complementary to SEM (Figures 6-8).…”

“…In the context of clays, the utilization of precipitating agents serves to mitigate soil dispersibility by reducing the thickness of the double layer, thereby diminishing the soil's susceptibility to erosion. For instance, Valencia-Galindo et al [29] used calcium chloride as a precipitating agent in their study of MICP in a soil containing expansive clays and sandy silts.…”

“…In that review, the previous results of researchers were selected, presented, analyzed, and summarized in order to be used as references for future studies. An interesting study was reported by Valencia-Galindo et al [29] on the evolution of the effectiveness of soil treatment using CaCO 3 precipitation from cultivated and lyophilized bacteria in soil-compaction water. The study investigated soils containing expansive clays and sandy silts.…”

Experimental Study on Silt Soil Improved by Microbial Solidification with the Use of Lignin

“…The experimental study of using microorganisms to improve unfavorable soil makes it possible to apply this method to engineering. Scholars have used MICP technology to improve unfavorable soil to varying degrees, including sand [ 40 , 41 , 42 ], silt [ 43 , 44 , 45 ], loess [ 46 , 47 , 48 , 49 , 50 ], expansive soil [ 51 , 52 , 53 , 54 ], and mucky soil [ 55 , 56 ], using this method, and the unconfined compressive strength and cohesion of the soil are significantly improved, which can be used in engineering practice. In the field of geotechnical engineering, the research results of MICP on soil improvement can be used for foundation reinforcement [ 57 , 58 , 59 ], earth dam reinforcement [ 60 ], wind prevention, sand fixation [ 61 ], reservoir bottom anti-seepage, and anti-seepage curtains [ 42 ].…”