Microbially Induced Calcite Precipitation Research Articles

Exploring Porosity’s Role in Stiffening Waste Concrete Conglomerates Synthesized with Microbial Calcite: A Micromechanical Analysis

Abstract Amidst environmental challenges, this study utilizes the innovative method of microbially-induced calcite precipitation (MICP) to explore its application in recycling waste concrete fines (WCF). Specifically, we scrutinize the role of porosity in the mechanical behavior of MICP-cemented WCF conglomerates. Through a series of indentation tests, the study provides force-displacement relationships from which the stiffness of the samples is calculated. The Young’s modulus of the samples is then estimated using Sneddon’s solution, which assumes a conical indenter and homogeneous elastic behavior. Subsequently, the Mori–Tanaka scheme with Eshelby’s solution is employed to predict the Young’s modulus of the samples with different porosity, allowing a comparison with the calculated stiffness. This work contributes to the understanding of the role of porosity in the mechanical behavior of MICP-cemented WCF specimens and offers a pathway for optimizing the production process of such materials. Graphical Abstract

Coupled multiphysical model for investigation of influence factors in the application of microbially induced calcite precipitation

The study presents a comprehensive coupled thermo-bio-chemo-hydraulic (T-BCH) modeling framework for stabilizing soils using microbially induced calcite precipitation (MICP). The numerical model considers relevant multiphysics involved in MICP, such as bacterial ureolytic activities, biochemical reactions, multiphase and multicomponent transport, and alteration of the porosity and permeability. The model incorporates multiphysical coupling effects through well-established constitutive relations that connect parameters and variables from different physical fields. It was implemented in the open-source finite element code OpenGeoSys (OGS), and a semi-staggered solution strategy was designed to solve the couplings, allowing for flexible model settings. Therefore, the developed model can be easily adapted to simulate MICP applications in different scenarios. The numerical model was employed to analyze the effect of various factors, including temperature, injection strategies, and application scales. Besides, a T-BCH modeling study was conducted on the laboratory-scale domain to analyze the effects of temperature on urease activity and precipitated calcium carbonate. To understand the scale dependency of MICP treatment, a large-scale heterogeneous domain was subjected to variable biochemical injection strategies. The simulations conducted at the field-scale guided the selection of an injection strategy to achieve the desired type and amount of precipitation. Additionally, the study emphasized the potential of numerical models as reliable tools for optimizing future developments in field-scale MICP treatment. The present study demonstrates the potential of this numerical framework for designing and optimizing the MICP applications in laboratory-, prototype-, and field-scale scenarios.

Feeding strategies for Sporosarcina pasteurii cultivation unlock more efficient production of ureolytic biomass for MICP.

The bacterium Sporosarcina pasteurii is the most commonly used microorganism for Microbial Induced Calcite Precipitation (MICP) due to its high urease activity. To date, no proper fed-batch cultivation protocol for S. pasteurii has been published, even though this cultivation method has a high potential for reducing costs of producing microbial ureolytic biomass. This study focusses on fed-batch cultivation of S. pasteurii DSM33. The study distinguishes between limited fed-batch cultivation and extended batch cultivation. Simply feeding glucose to a S. pasteurii culture does not seem beneficial. However, it was exploited that S. pasteurii is auxotrophic for two vitamins and amino acids. Limited fed-batch cultivation was accomplished by feeding the necessary vitamins or amino acids to a culture lacking them. Feeding nicotinic acid to a nicotinic acid deprived culture resulted in a 24% increase of the specific urease activity compared to a fed culture without nicotinic acid limitation. Also, extended batch cultivation was explored. Feeding a mixture of glucose and yeast extract results in OD600 of ≈70 at the end of cultivation, which is the highest value published in literature so far. These results have the potential to make MICP applications economically viable.

Predicting the precipitated calcium carbonate and unconfined compressive strength of bio-mediated sands through robust hybrid optimization algorithms

Biological soil stabilization through Microbial-Induced Calcite Precipitation (MICP) demonstrates the potential to be an eco-friendly and sustainable approach to enhance the strength properties of cohesionless granular soils. No systematic study has been performed so far in the literature on predicting the strength of bio-mediated sands prior to testing. In this study, to overcome this deficiency, based on a comprehensive set of experimental data compiled from literature, the amounts of Precipitated Calcium Carbonate (PCC) and Unconfined Compressive Strength (UCS) of MICP-treated sands are estimated through hybridizing Artificial Neural Network (ANN) and Adaptive Neuro-Fuzzy Inference System (ANFIS) models with metaheuristic algorithms. During the data extraction procedure, a total of 70 and 115 datasets are used to predict the PCC and UCS, respectively. To this end, five key features of urea concentration (Mu), calcium chloride (Mcc), optical density of bacterial suspension (OD600), pH and total volume of injection per volume of sample (Vt), are first selected as the inputs of the hybrid models to estimate the amount of calcium carbonate precipitation within the porous structure of MICP-treated granular medium. The experimental data on the PCC along with the basic characteristics of the host sand including mean grain size (D50), uniformity coefficient (Cu) and void ratio (e), are then adopted as the inputs of the numerical models in the second phase whilst the UCS of bio-mediated sands is set as the output. The performance and accuracy of implemented models are rigorously assessed through analyzing various statistical indices and performance criteria. According to the numerical analysis, the ANN-Particle Swarm Optimization (PSO) and ANFIS-PSO hybrid models show the best performance in predicting PCC and UCS of bio-mediated sands, respectively. Using the well-established Gene Expression Programming (GEP) algorithm, practical correlations are developed to predict the PCC and UCS values of MICP-mediated soils based on the characteristics of biological binding agents as well as the host material. The Machine Learning (ML)-based models presented in this study provide engineers with a fruitful framework for the rough and preliminary estimation of the amount of calcite precipitation as well as the UCS of bio-mediated sands in the field prior to stabilization and performing complementary tests. Nevertheless, it is important to consider the limitations of extrapolation in the models presented in this research.

Numerical analysis of MICP treated sand based on bio-chemo-hydro model.

Microbially Induced Calcite Precipitation (MICP) represents an environmentally friendly and innovative soil grouting technology. Involving intricate biochemical processes, it poses challenges for a thorough investigation of factors influencing microbial grouting effectiveness through experimentation alone. Consequently, A three-dimensional numerical model was developed to predict the permeability of bio-grouting in porous media. The numerical model is validated by comparing its results with test results available in the literature. The validated model is then used to investigate the effects of variation bacterial solution concentration, cementation solution concentration, grouting rate and grouting time on grouting effectiveness. It was founded that the remediation effect was positively correlated with the bacterial solution concentration and the number of grouting. An increased grouting rate enhanced the transport efficiency of reactants. Additionally, the concentration of cementation solution exhibited no significant effect on the reduction of calcium carbonate yield and permeability.

Investigating the potential of delignified rice husk as a carbon-rich resource for extracting glucose and its utilization in biocement production through fungal isolates.

Burning rice straw is now a significant issue faced by different regions in India, as its burning releases harmful gases, mainly carbon dioxide. Various techniques are now in trend to utilize the rice straw, e.g., producing compressed natural gas using rice straw, bioethanol, etc., as a substrate for various microorganisms. A high quantity of non-utilized rice husk generates more ideas for its proper utilization. The cellulose, hemicellulose, and lignin found in rice straws can be a fungi growth medium. In this research, the delignification of rice husk is done by acid (2% and 4% H2SO4) and alkali (2% and 4% NaOH) at 121°C at 103kPa for 1h to obtain crude carbon source which is further utilized for biomineralization. The glucose is subjected to qualitative and quantitative analysis using Molisch's and Dinitro salicylic tests. The delignification process showed a positive outcome when 2% H2SO4 is utilized maximum yield of 5.9 ug/ml free sugar concentration. Representing the highest glucose yield compared to the experiment's other acid and base substances used. Various techniques such as field emission-scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), and Fourier transformed infra-red (FTIR) spectroscopy are employed to examine surface and chemical alterations. The 2% H2SO4 pretreated rice husk is utilized for microbial-induced calcite precipitation using fungal isolates S1 (3), S1 (18), and S4 (1). The calcite and vaterite produced by biomineralization are confirmed using XRD for fungal isolates namely, S1 (3), S1 (18), and S4 (1) having percentage crystallinity of 59%, 46.428%, and 62.69% percentage crystallinity respectively.

Biomineralization of heavy metals based on urea transport and hydrolysis within a new bacterial isolate, B. intermedia TSBOI

A newly isolated ureolytic bacteria, Brucella intermedia TSBOI, exhibited microbially induced calcite precipitation (MICP) which is a promising technique for the remediation of heavy metals in polluted environments. Brucella intermedia TSBOI achieved 90–100% removal of 1 mmol/L Cu2+/Pb2+/Zn2+ within 72 h. A distinctive feature lies in B. intermedia TSBOI’s capacity for the transport and hydrolysis of urea, considered to be critical for its strong urease activity. This study explored the mechanisms of this capacity at the genetic, molecular and protein levels through complete genome sequencing, molecular docking and enzymatic reaction kinetics. The results revealed that, for urea hydrolysis, B. intermedia TSBOI exhibited a comprehensive urease gene cluster, with the key gene ureC demonstrating an absolute expression level approximating to 4 × 104 copies/RNA ng under optimal conditions. Results also confirmed the strong spontaneous, energy-independent binding ability of it’s urease to urea, with the lowest Gibbs free energy binding site linking to the three amino acids, alanine, asparagine and serine. The urea transport gene yut presented and expressed, with the absolute expression enhanced in response to increasing urea concentrations. The significant positive correlation between ureC/yut expression levels and urease activity provided a theoretical basis for B. intermedia TSBOI's heavy metal bioremediation potential. Environmental ImplicationHeavy metals (Cu, Pb and Zn) were studied in this study. Heavy metals are hazardous due to their toxicity, persistence, and ability to bioaccumulate in living organisms. They can cause severe health issues, harm ecosystems, and contaminate air, water, and soil. A novel ureolytic bacteria, Brucella intermedia TSBOI, exhibited microbially induced carbonate precipitation capability was isolated which removed 90–100% of 1 mmol/L Cu2+/Pb2+/Zn2+ within 72 h. Its advantages in urea hydrolysis and transport facilitate the remediation of actual heavy metal contaminated environments.

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 Wind Erosion Resistance of Aeolian Sand Solidified by Microbially Induced Calcite Precipitation (MICP).

Microbially induced calcite precipitation (MICP) is an emerging solidification method characterized by high economic efficiency, environmental friendliness, and durability. This study validated the reliability of the MICP sand solidification method by conducting a small-scale wind tunnel model test using aeolian sand solidified by MICP and analyzing the effects of wind velocity (7 m/s, 10 m/s, and 13 m/s), deflation angle (0°, 15°, 30°, and 45°), wind erosion cycle (1, 3, and 5), and other related factors on the mass loss rate of solidified aeolian sand. The microstructure of aeolian sand was constructed by performing mesoscopic and microscopic testing based on X-ray diffraction analysis (XRD), Fourier-transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). According to the test results, the mass loss rate of solidified aeolian sand gradually increases with the increase in wind velocity, deflation angle, and wind erosion cycle. When the wind velocity was 13 m/s, the mass loss rate of the aeolian sand was only 63.6%, indicating that aeolian sand has excellent wind erosion resistance. CaCO3 crystals generated by MICP were mostly distributed on sand particle surfaces, in sand particle pores, and between sand particles to realize the covering, filling, and cementing effects.

Optimized kernel extreme learning machine using Sine Cosine Algorithm for prediction of unconfined compression strength of MICP cemented soil.

Microbially induced calcite precipitation (MICP) is an eco-friendly bio-remediation technology. The unconfined compressive strength (UCS) of MICP cemented soil is an important indicator of repair effectiveness. This study proposes a machine learning technique utilizing the Sine Cosine Algorithm (SCA) to optimize the regularization coefficient C and kernel width γ of the kernel extreme learning machine (KELM) to predict the UCS of MICP cemented soil. To evaluate the performance of the proposed models, a dataset containing 180 groups of the UCS of MICP cemented soil was obtained. The results obtained by SCA-KELM were compared with those obtained by the Random Forest algorithm (RF), Support Vector Machine (SVM), and KELM. The performance of these models was evaluated by the scores of MAE, RMSE, and R2. The results indicate that the SCA-KELM algorithm exhibits optimal prediction performance (Total score: 21). After optimizing KELM with SCA, the total score improved by 110%, suggesting that SCA significantly enhances the KELM performance. After model development, the optimal population size for SCA-KELM was determined to be 50. Based on the mutual information test, an innovative method was developed for categorizing factor sensitivity by employing importance scores as the partitioning criterion. This method categorizes the influencing factors into three tiers: high (importance score: 8.03-11.14%), medium (importance score: 5.93-7.25%), and low (importance score: 3.23-5.18%). These results suggest that the proposed SCA-KELM algorithm can be regarded as a powerful tool for predicting the UCS of MICP cemented soil.

Indigenous Bacteria-Driven Eco-Friendly Soil Stabilization: A Bioinspired Approach Through Microbially Induced Calcite Precipitation for Sustainable Infrastructure Development

Indigenous Bacteria-Driven Eco-Friendly Soil Stabilization: A Bioinspired Approach Through Microbially Induced Calcite Precipitation for Sustainable Infrastructure Development

Biofilm Characterization and Establishing Microbial-Induced Calcite Precipitation Treatment Process for Ganga River Sand by Using the Sand Column Method

Biofilm Characterization and Establishing Microbial-Induced Calcite Precipitation Treatment Process for Ganga River Sand by Using the Sand Column Method

A bio-chemo-hydro-mechanical model of transport, strength and deformation for bio-cementation applications

AbstractBio-cementation through microbially induced calcite precipitation (MICP) has the potential to overcome several technical and environmental limitations of conventional cement-based soil improvement techniques. While a significant amount of research has been directed towards better understanding and controlling MICP processes, there is still a lack of multiphysical formulations that can be used for the design of real geotechnical applications in which both the treatment extent and its strength and deformability need to be evaluated. This paper presents the development and application of a comprehensive bio-chemo-hydro-mechanical model that can be used for designing MICP treatments with the finite element method. To overcome the limitations of current approaches based on elasticity, the formulation involves an elastoplastic constitutive model based on Mohr–Coulomb that can predict the strength increase of MICP-improved soils. The model can easily be calibrated with existing experimental results. The scope of model application is demonstrated through the case of a 2D shallow foundation strengthening. Results reveal that the questions of what level of cementation to target and how to distribute cementation efficiently are of equal importance to ultimately serve the needs of specific geotechnical problems, such as those of bearing capacity.

Experimental study on environmental chemical effect and purification treatment of waste slurry in horizontal directional drilling

The waste slurry generated during Horizontal Directional Drilling (HDD) has detrimental effects on water sources, soil, and organisms. Existing studies lack quantitative analysis and assessment of the environmental hazards of waste slurry. The treatment of waste slurry is usually done by physical curing or chemical curing agents. The treatment effect of these treatments is unsatisfactory or not environmentally friendly enough. Research on the application of Microbially Induced Calcite Precipitation (MICP) in waste slurry purification can help provide innovative solutions. This study began by acquiring the basic properties, mineral composition, and particle size distribution of the waste slurry through experiments. The effects of different concentrations of waste slurry on soil chemical properties were compared, including the measurement of total dissolved solids (TDS), turbidity, and heavy metal ion concentrations of waste slurry supernatant. Additionally, the environmental impact of the waste slurry was assessed from an electrochemical, turbidity, and ionic composition perspectively. A combination formulation containing 2.8 wt% urease, 5 wt% urea, and 3.5 wt% calcium chloride was used to purify the waste slurry. The supernatant of the MICP treated waste slurry undergoes electrochemical testing to evaluate the effectiveness of MICP technology for slurry treatment. The findings indicate that both chemical additives and stratum contaminants significantly contribute to slurry pollution. When the waste slurry constitutes more than 40 wt% of the soil mass fraction, the electrical conductivity (EC) of the soil surpasses the threshold of 1000 μs/cm, and the pH level rises to approximately 9.5, rendering it unsuitable for plant growth. Moreover, the TDS, turbidity, and heavy metal ion concentrations in the waste slurry supernatant exceed the permissible environmental discharge limits. Notably, the concentration of arsenic (As) exceeds the national standard by 18 times, cadmium (Cd) by 20 times, and selenium (Se) by 208 times, posing a high risk of environmental pollution. However, the comparison of ion concentrations in the supernatant before and after MICP treatment reveals that MICP demonstrates effective cementation and co-precipitation of heavy metal ions. MICP purified 66.6 % of arsenic (As), all cadmium (Cd), 75 % of phosphorus (P), and 76 % of selenium (Se) from the waste slurry supernatant. The results of this research contribute to the quantitative evaluation of the environmental hazards of waste slurry. It also helps to promote the application of MICP in waste slurry purification.

Mitigation of aeolian erosion of loess soil by Bio-Stimulated microbial induced calcite precipitation

Microbial-induced calcite precipitation (MICP) is a soil amelioration technique that addresses various environmental and engineering concerns. Here, we present a study focusing on aeolian erosion control of loess soil from the Negev Desert (Israel). Changes in the treated soil's chemical, physical, and microbial community (abundance and diversity) were characterized following bio-stimulation of native, urea-hydrolyzing soil bacteria to achieve MICP. Bio-stimulation of the loess soil was induced in liquid media (batch experiments) and by spraying soil trays with stimulation media (urea and yeast extract). These experiments showed that the Negev loess could be readily stimulated to induce bacterial urea hydrolysis. Three to four daily sprayings were sufficient to achieve effective bio-stimulation, evidenced by a high hydrolysis rate and an alkaline pH. Erodibility experiments on a decimeter scale (50 cm x 50 cm trays) were performed on loess sprayed with treatment media with varying concentrations of urea and CaCl2, with a constant 1:1 M ratio. The effectiveness of the treatments was studied in a wind tunnel and by image analysis of desiccation cracks. Upscaling of the experiments to the large trays revealed a more complicated reality with urease activity, community composition, and calcium carbonate precipitation depending on the concentration of the treatment medium. Specifically, we show that a twofold reduction in the area and length of the desiccation cracks can be achieved by spraying the soil with a 0.5 M solution, resulting in effective MICP or a high concentration treatment (>1M solution) without achieving MICP. Our results show that erosion mitigation in loess soil depends on an interplay between biotic and abiotic processes based on the treatment media concentration and provides a necessary step for upscaling the bio-stimulated MICP strategy for future field implementations.

Paper waste grown as a biocalcified foam: perspectives from a bacterial and design viewpoint

Abstract Biocalcification is a naturally occurring mineralisation phenomenon resulting from the urease produced by microorganisms inhabiting soil environments. This process, often referred to as microbially induced calcite precipitation (MICP), is primarily exploited in an engineering context for soil stabilisation and the repair of concrete structures. MICP represents an emerging area of research in architecture and design. In this paper, we discuss the appropriation of MICP on Papier Plume, a foam made of paper waste used in the context of ImpressioVivo: a design-led research project exploring the conception and fabrication of 3D-printed and bacterially induced bio-sourced materials for a circular design framework. In the light of a previous study based on two strategies of calcification: (1) direct inoculation (2) spraying, we – a team of two designers and a microbiologist – discuss the relevance of an immersion strategy applied to the dry paper foam substrate. By doing so, we reflect on the relevance of MICP as a material design process underpinned by sustainable and circularity concerns, from a design perspective, but also into an attempt to embrace the perspective of the bacteria supporting these experiments; namely Sporosarcina pasteurii.

Assessment of enhanced strength and stiffness properties of bio-engineered coal fly ash

This study investigates the use of urease-producing bacteria for microbial induced calcite precipitation (MICP) to enhance the mechanical properties of coal fly ash (CFA). Sporosarcina pasteurii was employed to treat CFA with cementation solutions over 7, 14, and 28 days. Biotreated samples exhibited improved compressive strength, shear strength, stiffness, and cohesion. Calcite precipitation increased, and permeability decreased with treatment cycles, resulting in a 78% reduction in permeability and 8% calcite precipitation in a 28-day cycle. X-ray diffraction (XRD) and scanning electron microscope (SEM) investigations support the improved engineering properties of bioengineered coal fly ash (BCFA) samples.

Effects of bacterial consortium enhanced recycled coarse aggregates on self‐healing concrete immobilized with Bacillus megaterium MTCC 1684 and Bacillus subtilis NCIM 2193

AbstractThe strength and durability properties of the recycled aggregate concrete (RAC) have been affected by the cracks and the weak interfacial transition zone (ITZ) of the recycled coarse aggregates (RCA). However, the mechanical and physical features of RCA can be improved by microbially induced calcite precipitation (MICP). Therefore, immobilization techniques were used to protect and maintain the high efficiency of Bacillus bacteria for the formation and precipitation of calcium carbonates in self‐healing concrete over a period of time. The objective of the present study was to show the viability of the immobilized bacterial consortium‐enhanced RCA to form self‐healing cracks. Further, the self‐healing capability of enhanced RCA was investigated along with two other immobilization methods, that is, RCA and hydrated lime and brick powder (HBr)‐immobilized bacteria. The experimental results show that the increase in the bio‐deposition time improved the physical and mechanical properties of the RCA. Further, subsequently 56 days of the healing incubation period, the immobilized consortium‐enhanced RCA concrete specimens completely healed the cracks of width 0.58 mm. However, the equivalent cracks of width 0.56 mm were also recovered by the HBr immobilized bacterial cultures. Furthermore, the field emission scanning electron microscope (FESEM), energy dispersive spectroscopy (EDS) and X‐ray diffraction (XRD) analysis revealed that the existence of precipitation at the crack surface was calcium carbonate with a regular cubic‐shaped and lamellar layer morphology. The outcomes of the current study show that consortium‐enhanced RCA has promising potential to develop self‐healing concrete with self‐repaired and improved durability properties in the concrete construction field.

Optimization of Injection Methods in the Microbially Induced Calcite Precipitation Process by Using a Field Scale Numerical Model

Microbially induced calcite precipitation (MICP) is a promising, more eco-friendly alternative method for landslide prevention and foundation reinforcement. In this study, we investigated the optimization of injection methods within the MICP process in porous media to enhance calcite mass and consolidation effect. The results demonstrated that staged injections with considerable advantages significantly improved precipitated calcite mass by 23.55% compared with continuous injection methods. However, extended retention times in staged injections reduced reinforcement effects. Moreover, setting the additional time in all injection methods can improve the consolidation area and effect without added injections. Apart from the injection methods, the changes in porosity and substance concentration also directly affected calcite masses and the reinforcement effect. Both the total calcite mass and the reinforcement effect should be taken into account when selecting appropriate injection methods. In terms of influencing factors on the total calcite mass, substance concentration ≫ average porosity ≫ additional time &gt; retention time in staged injection. For the consolidation effect, substance concentration ≫ retention time in staged injection &gt; average porosity ≫ additional time. The 5 h retention time in staged injections was recommended as the optimum injection method in the geotechnical conditions for average porosity from 0.25 to 0.45, with the changes in different reactant concentrations.

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.