Microbial-Induced Calcite Precipitation Treatment Research Articles

Preparation and research on cationic modified vermiculite with strong adsorption capacity for mineralizing bacteria

To address the challenge of low binding strength and inefficient adsorption between mineralized bacteria carrier and microorganisms., this study aims to develop a novel immobilized carrier (Vermiculite/AP-DE) by modifying the surface of carrier with cationic modified material 3-aminopropyltriethoxysilane (APTES), and diethylenetriamine (DETA). The negatively charged Sporosarcina pasteurii (S.p) can be tightly adsorbed onto the carrier's surface through the Coulomb force, thereby improving the efficiency of microbial induced calcite precipitation (MICP). The FT-IR results and Zeta points analysis show that —NH2 group was successfully introduced, and the carrier has a positive charge in the solution when pH < 9.74. Scanning electron microscope (SEM) images and Thermal gravimetric analyzer (TGA) results show that Vermiculite/AP-DE can tightly adsorb a large amount of microorganisms, and the calcite formation reached 30.5 % after MICP treatment, which is three times higher than traditional grouting materials. Sand reinforcement tests demonstrated that Vermiculite/AP-DE& S.p, as grouting material, exhibits a repair effectiveness on large-pore sand that surpasses traditional methods by more than threefold. This study provides a novel solution for MICP consolidation of coarse sand.

Experimental study on the influence mechanism of clay particles on the microbial treatment of granite residual soil

The content of clay particles has a key influence on the physical and mechanical properties of microbial solidified granite residual soil. Microbial-induced calcite precipitation (MICP) treatment method of “mixing + grouting” was used to prepare microbial solidified granite residual soil samples with different clay contents and to explore the influence of clay content on the reinforcement effect of microbial solidified granite residual soil. A series of direct shear tests, disintegration tests, and microscopic observation tests was conducted to quantitatively analyze the influence of clay content on the shear strength and disintegration resistance of microbial solidified granite residual soil. The conclusions are summarized as follows: the shear strength and disintegration resistance of granite residual soils solidified by MICP treatment were remarkably improved, with the shear strength increasing by 9%∼16% when the clay content varied from 10%∼40%. The internal friction angle of the granite residual soil with different clay contents increased and then decreased with the increase in clay content. The cohesion of the microbial solidified granite residual soil increased with the increase in clay content, and the internal friction angle reached a minimum of 20% clay content (17.27°), which is 31.85% lower than that of 0% clay content (25.34°). The cohesion of the microbial solidified granite residual soil reached a maximum of 40% clay content (39.54 kPa), which is 8.69 times higher than that of 0% clay content (4.55 kPa). The MICP treatment technology is capable of effectively improving the shear strength and disintegration resistance of granite residual soils. The MICP treated process produces calcium carbonate precipitates that link the sand particles and fill the pores between the soil particles, increasing the number of larger agglomerates in the granite residual soil, which is the essential reason for the improvement in the softening and disintegration of the granite residual soil when exposed to water.

Repair of Cracks in Concrete with the Microbial-Induced Calcite Precipitation (MICP) Method

Abstract In this study, the microbiologically-induced calcium carbonate precipitation (MICP) method was employed to examine its potential for repairing cracks in concrete. In addition, specific gravity and porosity values were measured to examine the effect of calcite formations on concrete surfaces and microstructures. Bacteria-supplemented concrete repaired cracks up to 0.4 mm wide by filling them with CaCO3. Furthermore, this study not only examined the healing of the width but also the length of cracks. However, as the width of the treated cracks decreased, their length increased. This indicated that the MICP treatment is more effective in a limited crack range. Specific gravity values increased, and porosity values decreased in concrete supplemented with calcifying bacteria. SEM analyses showed that calcite is a bacterial product that forms a very tight bond with a cement gel and that calcite fills visible cracks and voids and creates more of a void-free and undamaged concrete structure.

Investigation of the effect of microbial-induced calcite precipitation treatment on bio-cemented calcareous sands using discrete element method

Owing to the bio-geological origin, calcareous sands are characterized by irregular particle shapes and abundant internal pores. These weak soil structures undergo extensive particle breakage under specific stress conditions. In recent years, microbial-induced calcite precipitation (MICP), a green soil treatment technique, has been widely utilized to improve the mechanical properties of calcareous sands. The treatment effect of MICP on calcareous sands and the underlying mechanism are still relatively unclear owing to the complex microstructures of the sands. This study investigated the micromechanism of MICP treatment on calcareous sands via the discrete element method (DEM). First, a group of calcareous sand particles were individually treated via a proposed MICP process. Single-particle crushing tests were conducted on the MICP-treated calcareous particles and a control group of untreated calcareous particles. The experimental results were further used to verify and calibrate the DEM models and parameters. The DEM model of MICP-treated calcareous particles was established via a novel modeling technique using the commercial PFC3D platform, which considered the inter-particle bridging and intra-particle pore filling effects by MICP treatment. Through this method, a series of MICP-treated calcareous sand samples subjected to uniaxial compression were simulated. The effects of calcite content and its spatial non-uniformity on the compression behaviors of the bio-cemented calcareous sand samples were studied. The micromechanics in terms of crack propagation and distribution as obtained from DEM were investigated to elucidate the mechanism of the MICP treatment of calcareous sands.

The effect of microbes on the stability of an unsaturated tropical slope

Conventional geotechnical practice considers that soil is an inert construction material and its engineering properties do not change with time. However, soil is a living ecosystem, and its engineering properties naturally change as a stable ecological system is gradually established following initial construction. Over the last few decades, researchers started exploring a way to engineer some microorganisms’ activities in order to solve problems in geotechnical engineering. This paper assesses the effect of a biostimulated Microbial Induced Calcite Precipitation (MICP) on the stability of an unsaturated tropical slope. For that, data from an experimental characterisation study carried out for a tropical soil was used. For the assessment of the stability of the slope, a critical rainfall for the region was considered and the pore water pressure distribution was obtained. The stability of the slope was assessed using a ‘simplified’ shear strength criterion formulated in terms of unsaturated cohesion. Results show that the MICP treatment contributes to the stability of the slope. This positive contribution is more significant than the contribution of suction towards the stability of the slope.

Increasing the Strength Properties in weak Soil Using Microbial Techniques

In Microbial-Induced Calcite Precipitation (MICP) has been introduced in the field of ground improvement. The applications of this method shows potential in several fields like improvement of strength and durability of concrete, bricks, sand permeability, soil strength etc., and various works are being conducted on these fields in the current scenario. To promote the engineering properties of the material after MICP treatment, need to have study the relevant crystal mineralization process and analyses the influences on the soil engineering properties. The main aim of this paper is to analyses the behavior of various bio geo chemical processes between the soil mineralogy, solid soil grains, water or fluid, and gases in the voids, beneath the soil surface after employing microbes as strengthening consultant. Geotechnical applications currently being inquired which includes the process of cementation of sands, to enhance bearing capacity and liquefaction resistance, Carbon sequestration, erosion control of soil, controlling the groundwater flow, and remediation of soil and groundwater impacted by metals and radio-nuclides.

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

This study explored the effect of indigenous bacteria present in the soil to stabilized swelling behavior and improving the mechanical property of expansive soil. The objective of the research is to investigate the effectiveness of the biostimulation microbial induced calcite precipitation (MICP) for controlling the swelling-shrinkage behavior and improving shear strength of expansive soil. An attempt was made to develop an effective procedure to culture the indigenous bacteria for treating clays with varying plasticity and improve their engineering behavior. The detailed procedure has been investigated to effectively apply the MICP technique in clay soil, considering its low permeable nature. The applicability of biostimulation to clayey soils in minimizing their swelling potential and improving the strength is assessed. Both macroscale and microscale studies were conducted on untreated and biostimulated soils to observe changes in plasticity, strength, swelling, mineralogical, chemical characteristics. The present method has shown an effective alternative to improve the road pavement subgrade without affecting the eco-system of natural soil. The method investigated the effective way of providing the enrichment and cementation solution in clayey soil, which is the major concern in current literature. The study confirms that the calcite content has been increased with biostimulated MICP treatment up to 205% in the treated specimens and which future increased the unconfined compressive strength and split tensile strength. A reduction in the swelling pressure and swell strain is also observed. The results show that a cost-effect and eco-friendly method can be deployed for stabilizing the road pavement subgrades. The statistical assessment using multivariate analysis and hierarchical clustering dendrogram has been carried out to investigate the effect of the MICP treatment protocol on different soil and engineering parameters.

Applications of bio-cementation and bio-polymerization for aeolian erosion control

This study investigates soil stabilization through two soil strengthening techniques, specifically; Bio-cementation through Microbial induced calcite precipitation (MICP) and Bio-polymerization using Xanthan gum for aeolian erosion control applications. The performances of these techniques were evaluated in terms of improvement in Threshold friction velocity (TFV), soil mass loss (%), and soil crust thickness formed with different levels of the treatment by conducting a series of experiments in the laboratory-scale wind tunnel and the microstructural observations with the help of FESEM and X-ray diffraction techniques. The results from wind erosion studies exhibited an improvement in TFV from 20 km/h for untreated to 45 km/h for MICP and biopolymer treated sand. A reduction in the soil mass loss from 75.23% for untreated to as least as 0% with both MICP and biopolymer treatment was observed. The results also indicated that the concentration of urea-cacl2 and biopolymer both played a critical role in soil improvement in both treatment methods. In MICP treated soil, the maximum wind speed of 45 km/h was encountered as TFV with 0.5M urea-cacl2. Whereas the TFV of biopolymer treated soil encountered the maximum wind speed of 45 km/h with a minimum of 0.25% of Xanthan Gum biopolymer solution.

Dolerite Fines Used as a Calcium Source for Microbially Induced Calcite Precipitation Reduce the Environmental Carbon Cost in Sandy Soil.

Microbial-Induced Calcite Precipitation (MICP) stimulates soil microbiota to induce a cementation of the soil matrix. Urea, calcium and simple carbon nutrients are supplied to produce carbonates via urea hydrolysis and induce the precipitation of the mineral calcite. Calcium chloride (CaCl2) is typically used as a source for calcium, but basic silicate rocks and other materials have been investigated as alternatives. Weathering of calcium-rich silicate rocks (e.g., basalt and dolerite) releases calcium, magnesium and iron; this process is associated with sequestration of atmospheric CO2 and formation of pedogenic carbonates. We investigated atmospheric carbon fluxes of a MICP treated sandy soil using CaCl2 and dolerite fines applied on the soil surface as sources for calcium. Soil-atmosphere carbon fluxes were monitored over 2 months and determined with an infrared gas analyser connected to a soil chamber. Soil inorganic carbon content and isotopic composition were determined with isotope-ratio mass spectrometry. In addition, soil-atmosphere CO2 fluxes during chemical weathering of dolerite fines were investigated in incubation experiments with gas chromatography. Larger CO2 emissions resulted from the application of dolerite fines (116 g CO2-C m–2) compared to CaCl2 (79 g CO2-C m–2) but larger inorganic carbon precipitation also occurred (172.8 and 76.9 g C m–2, respectively). Normalising to the emitted carbon to precipitated carbon, the environmental carbon cost was reduced with dolerite fines (0.67) compared to the traditional MICP treatment (1.01). The carbon isotopic signature indicated pedogenic carbonates (δ13Cav = −8.2 ± 5.0‰) formed when dolerite was applied and carbon originating from urea (δ13Cav = −46.4 ± 1.0‰) precipitated when CaCl2 was used. Dolerite fines had a large but short-lived (<2 d) carbon sequestration potential, and results indicated peak CO2 emissions during MICP could be balanced optimising the application of dolerite fines.

Effects of Microbial Biomineralization Surface Erosion Control Treatments on Vegetation and Revegetation along Highways

Microbial induced calcite precipitation (MICP) has been widely studied in laboratories to test changes to soil strength and density. Rarely studied is the biogeotechnology’s influence on real-world conditions. Consideration for the natural environment coexisting with treated soil is important, particularly vegetative responses to biochemical and physical changes from treatments. In this factorial designed study, vegetative response from one-time biochemical surficial treatments is observed in four soil growth mediums: two variants burned soil, unburned side slope construction soil, and Ottawa sand. Treatment objectives are to create a light crust that provides short-term erosion control, protects concurrently applied seeds and provides a beneficial plant environment (BPE). The crust creates a BPE through increased soil water retention and shear soil strength allowing better root and plant stability. An overly dense crust prevents root penetration and is avoided because established root systems are crucial in long-term erosion control. This study successfully created such a crust in all soil types treated. Also studied were influences of solution components on germination rates. Component influence proved highly dependent on soil type as calcium chloride inclusion was highly detrimental to seedling success in clean sand, somewhat detrimental to burned soil with ash layer, insignificant in unburned soil, and beneficial to burned soil without ash layer. These results give an indication of the complex biochemical soil reactions occurring from MICP treatment. This study gives evidence that a one-time application of a seeded biochemical solution has real-world potential as a balanced short-term and long-term erosion control technology for burned and construction soils.

Desiccation Cracking Behavior of Clayey Soils Treated with Biocement and Bottom Ash Admixture during Wetting–Drying Cycles

Desiccation cracking considerably impairs the hydraulic and mechanical properties of clayey soils that are critical to the long-term performance of infrastructure foundations and earth structures. Typical crack remediation methods are associated with high labor and maintenance costs or the use of environmentally unfriendly chemicals. Recycling waste materials and developing biomediated techniques have emerged as green, sustainable soil stabilization solutions. The objective of this study was to investigate the feasibility of soil crack remediation through use of bottom ash admixtures and microbial-induced calcite precipitation (MICP). We carried out cyclic wetting–drying tests to characterize the effects of bottom ash and MICP on the desiccation cracking behaviors of bentonite soils. Two groups of soil samples that contained different percentages of bottom ash (0%, 20%, 40% by weight) were prepared for cyclic water and MICP treatments, respectively. The desiccation cracking patterns captured by a high-resolution camera were quantified using image processing. We also employed scanning electron microscopy for microstructural characterizations. Experimental results revealed that cyclic water treatment resulted in more cracking, whereas cyclic MICP treatment improved soil strength owing to the precipitation of calcite crystals on the soil particle surface and inside the interparticle pores. Adding bottom ash to bentonite reduced the plasticity of the mixture, promoted the flocculation of clay particles by cation exchange, and also provided soluble calcium to enhance calcite precipitation. This study demonstrates the potential of bottom ash and MICP for crack remediation and brings new insights into the design and assessment of sustainable infrastructures under climate changes.

Desiccation Cracking Behavior of MICP-Treated Bentonite

This study aims to characterize the effect of microbial-induced calcite precipitation (MICP) on the desiccation cracking behaviors of compacted calcium bentonite soils. We prepare six groups of samples by mixing bentonites with deionized water, pure bacteria solution, pure cementation solution, and mixed bacteria and cementation solutions at three different percentages. We use an image processing tool to characterize the soil desiccation cracking patterns. Experimental results reveal the influences of fluid type and mixture percentage on the crack evolution and volumetric deformation of bentonite soils. MICP reactions effectively delay the crack initiation and remediate desiccation cracking, as reflected by the decreased geometrical descriptors of the crack pattern such as surface crack ratio. The mixture containing 50% bacteria and 50% cementation solutions maximizes the MICP treatment and works most effectively in lowering the soil cracking potential. This study provides new insights into the desiccation cracking of expansive clayey soils and shows the potential of MICP applications in the crack remediation.

Development of a Rigid Full-Contact Mold for Preparing Biobeams through Microbial-Induced Calcite Precipitation

Abstract As a new environmentally friendly and sustainable technique for soil improvement, microbial-induced calcite precipitation (MICP) has been studied widely. A suitable sample preparation mold is the first step to prepare MICP treatment. The purpose of this study is to develop a rigid full-contact mold to prepare larger biobeam specimens for MICP treatments with an immersing method. Four different molds were developed, including a plastic beam rigid mold without a cover, a full-contact flexible mold, a rigid full-contact mold with geotextiles, and a rigid full-contact mold with filter paper. Beam-shaped specimens with different dimensions were treated with the four molds in the MICP process. A four-point bending test and a split tensile strength test were conducted to evaluate the flexural behavior of MICP-treated specimens from the four sample preparation molds. The results indicated that an MICP-treated sample prepared by the rigid full-contact mold with geotextiles can form the best beam shape and the most uniform calcite precipitation inside the sample. Additionally, the biobeam made by the rigid full-contact mold with geotextiles achieved the best mechanical properties. The flexural strength of the biobeam made by the rigid full-contact mold was 1,125 kPa at a failure flexural strain of 1.5 %, and the split tensile strength was 368 kPa with a failure tensile strain of 1.8 %.

Experimental investigation of flexure resistance performance of bio-beams reinforced with discrete randomly distributed fiber and bamboo

Microbial induced calcite precipitation (MICP) can bond sand particles together to improve the mechanical properties of sandy soil. This environmental-friendly technique has potential applications on construction materials such as bio-bricks and bio-beams. This study is to investigate the flexure resistance performance of bio-beams by adding discrete randomly distributed fiber and bamboo materials with multiple immersing MICP treatment. Different fiber proportions (0.1%, 0.2%, 0.3% and 0.4% by weight of dry sand) were used. MICP treated bio-beams were also reinforced by five different arrangements of bamboo strips. Four-point bending tests were conducted to evaluate the flexure behavior of fiber reinforced and bamboo reinforced bio-beams. Results showed that adding fiber in the MICP treated bio-beams can increased the ductility. The optimum fiber content was around 0.3%. Addition of 0.3% fiber can significantly prevent the post peak flexure strength loss and improved the ductility of bio-beams which had 400 kPa residual strength at 15% failure strain. Bamboo reinforced bio-beam can improve the flexure strength from 890 kPa to 1750 kPa. Meanwhile, multiple immersing MICP treatment can significantly improve the flexure strength of bio-beams up to 3.0 MPa, but the ductility of fiber reinforced bio-beam reduced after multiple treatment.

Evaluation of Shear Strength Parameters of Sandy Soils upon Microbial Treatment

ABSTRACTA new method for soil stabilization known as microbial-induced calcite precipitation (MICP) has been the focus of research in this area during the last decade. In this method, the reaction of microorganisms in the presence of urea and calcium chloride is used to produce calcite. Despite the large numbers of bacteria in soil, Sporobacillus pasteurii (previously known as Bacillus pasteurii) has the most capability to create cementation between soil particles in the MICP method due to its high urease activity. In this paper, the effect of MICP treatment on the shear strength characteristics of a sandy soil was studied. The change in the shear strength of sandy soil upon MICP treatment was measured using a strain-controlled direct shear test before and after treatment of the soil samples. The results showed an increase of 44–86% in the shear strength of the sandy soil after 15 days of MICP treatment compared to the untreated soil. The enhanced shear strength was the result of an increase in both the cohesion intercept and angle of internal friction. The increase in the cohesion intercept was more significant than the increase in the angle of internal friction.

Effect of Reagents Concentration on Biocementation of Tropical Residual Soil

This study explores the feasibility of Bacillus subtilis and optimum reagents concentration used in Microbial-Induced Calcite Precipitation (MICP) treatment of tropical residual soil. Experiment was conducted to investigate the effect of cementation reagents concentration toward MICP treatment. The performance of MICP treatment was assessed by measurement of the soil shear strength and calcite content. Based on the experimental results, it is discovered that the cementation reagent concentration has significantly affected on the performance of MICP treatment. The results suggested that the most preferable MICP treatment reagents concentration is 0.25M with the presence of Bacillus subtilis; using these treatment parameters, both UCS value and calcite content of treated soil had increased about 38% and 65.6% respectively. However, the reduction in UCS value was manifested for those samples treated at higher reagents concentration (0.35M); this phenomenon is attributed to the salinity of reagents where high salinity is not favourable to the bacteria growth and microbial activity; subsequently, this resulted in a consequential decrease in shear strength of the treated soil.

Bio-geochemical reactive transport modeling of microbial induced calcite precipitation to predict the treatment of sand in one-dimensional flow

Microbial induced calcite precipitation (MICP) has been well studied to date in the laboratory as a viable alternative soil improvement technique that harnesses a natural bacterial process to induce cementation. Specifically, MICP utilizes the microbial process of hydrolysis of urea to induce pH increase leading to calcite precipitation. The study presented herein demonstrates the utility of a simple bio-geochemical reactive transport model to predict MICP in one-dimensional column experiments. The mathematical model was originally developed in the framework of the TOUGHREACT code to include kinetically controlled reaction rates for urea hydrolysis and calcite precipitation. Inverse modeling, via UCODE-2005, is utilized to calibrate and verify the model to experimental data including aqueous and mineral chemistry. Results indicate good agreement between data and simulated results for capturing the trends and magnitudes of a variety of MICP treatment schemes in half meter, one-dimensional flow columns. A design procedure is presented for predicting MICP in one-dimensional flow by sequentially coupling UCODE-2005 with TOUGHREACT.

Healing of biologically induced cemented sands

Microbial-induced calcite precipitation (MICP) is a novel bio-mediated ground improvement method that can be used to increase the shear strength and stiffness of sand. One of the benefits of the MICP treatment process is the ability to heal degraded calcite bonds post-shearing. The healed bonds can then improve the sand properties (small strain stiffness and peak strength) compared with those of the pre-shearing condition. The MICP healing process was evaluated using monotonic undrained shearing and dynamic centrifuge tests, and comparing the sand behaviour before and after the healing process. Similar or improved behaviour was observed after the healing process. This healing ability implies that degraded MICP-treated sands can be healed after loading (e.g. in an earthquake) to their original level of treatment to prevent additional settlements or damage from subsequent loading (e.g. aftershocks).

Improvements in engineering properties of soils through microbial-induced calcite precipitation

Microbial-Induced Calcite Precipitation (MICP) has recently emerged as a sustainable technique for soil improvement. This paper aims to study the effectiveness of MICP in improving the shear strength and reducing the hydraulic conductivity of soils. A species of Bacillus group, B. megaterium was used to trigger the calcite precipitation. The experimental variables included soil types (tropical residual soil and sand), soil densities (85%, 90%, and 95% of their respective maximum densities), and treatment conditions (untreated, treated with cementation reagents only, treated with B. megaterium only, and treated with B. megaterium and cementation reagents). The results showed that MICP could effectively improve shear strength and reduce hydraulic conductivity for both residual soil and sand. The improvements, however, varied with soil densities, soil types, and treatment conditions. With MICP treatment, the improvement ratios in shear strength of the residual soil specimens were significantly higher (1.41–2.64) than those of the sand specimens (1.14–1.25). On the contrary, the sand specimens resulted in greater hydraulic conductivity reduction ratios (0.09–0.15) than those of the residual soil specimens (0.26–0.45). These observations can be explained by the particle-particle contacts per unit volume and pore spaces in the soil specimens. Both soil specimens when treated with cementation reagents only exhibited slight alterations in the shear strength (ranging from 1.06–1.33) and hydraulic conductivity (ranging from 0.69–0.95). The results implied that natural calcite forming microorganisms only exist for insignificant amount. The amount of calcite precipitated in the treated residual soil specimens ranged from 1.080% to 1.889%. The increments of calcite content in the treated sand specimens were comparatively higher, ranging from 2.661% to 6.102%. The results from Scanning Electron Microscope (SEM) analysis confirmed the experimental findings.