Microbial-Facilitated Calcium Carbonate Precipitation as a Shallow Stabilization Alternative for Expansive Soil Treatment

Abstract

Expansive soils generally recognized as swell-shrink soils have been a problem for civil infrastructure for a long time. Engineers are in search of sustainable stabilization alternatives to counter these problematic soils. Microbial-induced calcium carbonate precipitation (MICP) is a promising biocementation process that can improve the properties of expansive soil through calcium carbonate precipitation. Past research has shown promise for the use of MICP in mitigating swelling distress from expansive soils. In this research, MICP via biostimulation was attempted by mixing enrichment and cementation solutions with soils in an effort to develop a new alternative to shallow chemical stabilization. Three soils with varying clay contents (30%, 40%, and 70%) and plasticity characteristics were selected, and soils were treated by mixing with enrichment solutions followed by cementation solutions. Five different mellowing periods, three different curing periods, and two types of cementation solutions were studied to optimize the method. Treatment effectiveness was evaluated using unconfined compression tests, calcium carbonate tests, and free swell index tests. Results showed that an increase in the mellowing period beyond two days was not beneficial for any of the three soils tested in this research. It was determined that the best improvement was observed at two days of mellowing and seven days of curing.

An electrokinetic-biocementation study for clay stabilisation using carbonic anhydrase-producing bacteria

“…Indicatively however, we can mention that in Safdar et al ( 2021b ), who treated a soil with 50.8% organic content, CaCO 3 contents of an average of 1.25% corresponded to an average UCS increase of 110 kPa, whereas Duraisamy ( 2016 ) performing sand biocementation by deep mixing recorded UCS between 120 and 200 kPa for CaCO 3 contents between 0.8 and 1.33%, which are not very different to those recorded here for the biostimulation treatment. Finally, in Chittoori et al ( 2021 ) who applied biocementation treatments to an expansive clay of 70% clay content, as well as to mixtures of this clay with sand, to obtain soils of 40% and 30% contents of clay respectively, UCS results were very variable depending on treatment protocol and CaCl 2 content and did not always reflect measured CaCO 3 contents. For example, UCS increases for the soil containing 40% clay (similarly to the soil in our study) of 47 kPa, 96 kPa, and 101 kPa were noted respectively for CaCO 3 contents of 1.1%, 1.07%, and 0.97% for the lower CaCl 2 content used or, for the higher CaCl 2 content used, 25 and 32 kPa increases were noted for 0.82% and 0.68% of CaCO 3 , respectively.…”

Prospective Roles of Extremophilic Fungi in Climate Change Mitigation Strategies

“…[ 53 , 54 ]. As per the extensive hyphal networks, AM fungi can reach through the soil particles and enhance the water uptake ability of plants from below the ground [ 55 ]. These fungi can also influence the moisture-retaining characteristic of soil by enhancing the soil aggregates [ 56 , 57 ].…”

Effect of Microbial Stabilization on High, Intermediate and Low Compressible Clay

“…The MICP approach is an enhanced and more ecologically sustainable alternative to traditional technologies. Microbes are the main stabilizing component in the aforementioned strategy [5][6][7]. Through their metabolic activity, microorganisms have induced calcium carbonate precipitation into the soil structure to improve the engineering features of the soil.…”

“…A wide range of civil engineering fields will benefit from the successful application of MICP, encompassing retaining wall, embankment, and dam firmness, controlling soil erosion, maintaining cohesionless soils for facilitating the stability of underground constructions, improving the bearing capacity of shallow and piled foundations, and reducing the liquefaction potential of soil, etc. [6][7][8][9][10][11][12].…”