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Keywords = microbially induced calcite precipitation (MICP)

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28 pages, 5160 KiB  
Article
Comparative Study of Mechanical and Microstructural Properties of Biocemented Sandy Soils Enhanced with Biopolymer: Evaluation of Mixing and Injection Treatment Methods
by Mutlu Şimşek, Semet Çelik and Harun Akoğuz
Appl. Sci. 2025, 15(14), 8090; https://doi.org/10.3390/app15148090 - 21 Jul 2025
Viewed by 276
Abstract
Soil improvement is one of the fundamental practices in civil engineering, with a long-standing history. In today’s context, the rapidly increasing demand for construction driven by urbanization has further emphasized the necessity and significance of soil stabilization techniques. This study aims to determine [...] Read more.
Soil improvement is one of the fundamental practices in civil engineering, with a long-standing history. In today’s context, the rapidly increasing demand for construction driven by urbanization has further emphasized the necessity and significance of soil stabilization techniques. This study aims to determine the optimum parameters for improving sandy soils by incorporating sodium alginate (SA) as a biopolymer additive into the microbial calcium carbonate precipitation (MICP) process. Sand types S1, S2, and S3, each with distinct particle size distributions, were selected, and the specimens were prepared at medium relative density. Three distinct approaches, MICP, SA, and MICP + SA, were tested for comparison. Additionally, two different improvement methods, injection and mixing, were applied to investigate their effects on the geotechnical properties of the soils. In this context, hydraulic conductivity, unconfined compressive strength (UCS), and calcite content tests, as well as scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) analyses, were performed to assess the changes in soil behavior. SA contributed positively to the overall efficiency of the MICP process. The study highlights SA-assisted MICP as an alternative that enhances the microstructural integrity of treated soils and responds to the environmental limitations of conventional methods through sustainable innovation. Full article
(This article belongs to the Section Civil Engineering)
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21 pages, 3584 KiB  
Article
Interpretable Ensemble Learning with Lévy Flight-Enhanced Heuristic Technique for Strength Prediction of MICP-Treated Sands
by Yingui Qiu, Shibin Yao, Hongning Qi, Jian Zhou and Manoj Khandelwal
Appl. Sci. 2025, 15(14), 7972; https://doi.org/10.3390/app15147972 - 17 Jul 2025
Viewed by 206
Abstract
Microbially-induced calcite precipitation (MICP) has emerged as a promising bio-geotechnical technique for sustainable soil improvement, yet accurate prediction of treatment effectiveness remains challenging due to complex multi-factor interactions. This study develops an ensemble learning framework (LARO-EnML) for predicting the unconfined compressive strength (UCS) [...] Read more.
Microbially-induced calcite precipitation (MICP) has emerged as a promising bio-geotechnical technique for sustainable soil improvement, yet accurate prediction of treatment effectiveness remains challenging due to complex multi-factor interactions. This study develops an ensemble learning framework (LARO-EnML) for predicting the unconfined compressive strength (UCS) of MICP-treated sand. A comprehensive database containing 402 experimental datasets was utilised in the study, consisting of unconfined compression test results from bio-cemented sands with eight key input parameters considered. The performance evaluation demonstrates that LARO-EnML achieves superior predictive accuracy, with RMSE of 0.5449, MAE of 0.2853, R2 of 0.9570, and OI of 0.9597 on the test data, significantly outperforming other models. Model interpretability analysis reveals that calcite content serves as the most influential factor, with a strong positive correlation to strength enhancement, while urease activity exhibits complex, staged influence characteristics. This research contributes to advancing the practical implementation of MICP technology in geotechnical engineering by offering both accurate predictive capability and enhanced process understanding through interpretable ML approaches. Full article
(This article belongs to the Special Issue Applications of Machine Learning in Geotechnical Engineering)
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18 pages, 1437 KiB  
Article
Exploration of Microbially Induced Carbonate Precipitation Technology for the Protection of Soil on Agricultural Drainage Ditch Slopes
by Xinran Huang, Jiang Li, Mingxiao Su, Xiyun Jiao, Qiuming Wu and Zhe Gu
Water 2025, 17(13), 2010; https://doi.org/10.3390/w17132010 - 4 Jul 2025
Viewed by 379
Abstract
Microbially induced carbonate precipitation (MICP) offers an eco-friendly approach to stabilize porous materials. This study evaluates its feasibility for protecting agricultural drainage ditch slopes through laboratory tests. Liquid experiments assessed calcium carbonate (CaCO3) precipitation rates under varying bacteria–cementation solution ratios (BCR), [...] Read more.
Microbially induced carbonate precipitation (MICP) offers an eco-friendly approach to stabilize porous materials. This study evaluates its feasibility for protecting agricultural drainage ditch slopes through laboratory tests. Liquid experiments assessed calcium carbonate (CaCO3) precipitation rates under varying bacteria–cementation solution ratios (BCR), cementation solution concentrations (1–2 mol/L), and urease inhibitor (NBPT) contents (0–0.3%). Soil experiments further analyzed the effects of solidified layer thickness (4 cm vs. 8 cm) and curing cycles on soil stabilization. The results showed that CaCO3 precipitation peaked at a BCR of 4:5 and declined when NBPT exceeded 0.1%. Optimal parameters (0.1% NBPT, 1 mol/L cementation solution, BCR 4:5) were applied to soil tests, revealing that multi-cycle treatments enhanced soil water retention and CaCO3 content (up to 7.6%) and reduced disintegration rates (by 70%) and permeability (by 83%). A 4 cm solidified layer achieved higher Ca2+ utilization, while an 8 cm layer matched or exceeded 4 cm performance with shorter curing. Calcite crystals dominated CaCO3 formation. Crucially, reagent dosage should approximate four times the target layer’s requirement to ensure efficacy. These findings demonstrate that MICP, when optimized, effectively stabilizes ditch slopes using minimal reagents, providing a sustainable strategy for agricultural soil conservation. Full article
(This article belongs to the Section Water, Agriculture and Aquaculture)
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17 pages, 1667 KiB  
Article
Evaluating the Contribution of Sporosarcina to Carbonate Precipitation in Anaerobic Soils: A Microbial Community and Quantitative Analysis
by Zen-ichiro Kimura, Ko-shiro Kirihara, Saki Komoto, Wataru Sera, Ryota Kojima, Sota Ihara, Yuya Itoiri, Daisuke Tanikawa and Yuki Iwasaki
Appl. Microbiol. 2025, 5(2), 53; https://doi.org/10.3390/applmicrobiol5020053 - 30 May 2025
Viewed by 765
Abstract
Microbially induced calcite precipitation (MICP) has attracted attention as an environmentally friendly soil stabilization method, with Sporosarcina pasteurii being a key ureolytic bacterium in this process. However, its behavior in oxygen-limited environments remains poorly understood, limiting the predictability of MICP outcomes in natural [...] Read more.
Microbially induced calcite precipitation (MICP) has attracted attention as an environmentally friendly soil stabilization method, with Sporosarcina pasteurii being a key ureolytic bacterium in this process. However, its behavior in oxygen-limited environments remains poorly understood, limiting the predictability of MICP outcomes in natural soils. This study investigated the population dynamics of Sporosarcina in compacted soil reactors operated under aerobic and anaerobic conditions, including saturated environments. Quantitative PCR and 16S rRNA gene sequencing revealed that Sporosarcina thrived and became dominant under aerobic, unsaturated conditions, but failed to maintain a high abundance under anaerobic or saturated conditions. These findings indicate that gas-phase oxygen—not merely its presence in the overlying atmosphere—is essential for effective Sporosarcina-driven MICP. The results highlight a critical environmental constraint that limits the application of biostimulation strategies relying on indigenous Sporosarcina in oxygen-poor soils. This study provides the first in situ evidence linking oxygen availability and microbial dominance in MICP systems, with implications for optimizing microbial soil stabilization in real-world conditions. Full article
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21 pages, 6227 KiB  
Article
A One-Phase Injection Method with Dual Inhibition for Improving the Strength and Uniformity of MICP
by Yanni Huang, Fengyin Liu and Xiangtong Zhang
Materials 2025, 18(11), 2514; https://doi.org/10.3390/ma18112514 - 27 May 2025
Viewed by 401
Abstract
The formation and spatial uniformity of calcium carbonate (CaCO3) are critical for evaluating the effectiveness of microbial-induced calcium carbonate precipitation (MICP) in geotechnical applications. In recent years, the single-phase injection method has emerged as a promising alternative to traditional two-phase processes [...] Read more.
The formation and spatial uniformity of calcium carbonate (CaCO3) are critical for evaluating the effectiveness of microbial-induced calcium carbonate precipitation (MICP) in geotechnical applications. In recent years, the single-phase injection method has emerged as a promising alternative to traditional two-phase processes by addressing the issue of uneven CaCO3 distribution. This study proposes a dual inhibition strategy that delays the mineralization reaction by synergistically lowering pH and temperature, thereby promoting uniform precipitation and enhanced compressive strength in cemented sand columns. A series of experiments, including bacterial growth, aqueous reaction, sand column reinforcement, and microstructural characterization, were conducted. Results show that the minimum pH required for flocculation increases from ~4.5 at 40 °C to ~6.0 at 10 °C. Under dual inhibition, the lag period effectively improved the spatial uniformity of CaCO3 and enabled complete calcium utilization within 24 h. After four treatment cycles, the CaCO3 content at 10 °C increased by 53%, and the unconfined compressive strength reached 2.5 MPa, a 50% improvement over the 40 °C condition. XRD analysis confirmed that calcite was the dominant phase (85–90%), accompanied by minor vaterite. These findings demonstrate the adaptability and efficiency of the dual inhibition method across temperature ranges, providing a cost-effective solution for broader engineering applications. Full article
(This article belongs to the Section Biomaterials)
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16 pages, 6717 KiB  
Article
Ureolysis-Driven Microbially Induced Carbonate Precipitation by a Facultatively Anaerobic Thermophilic Bacterium Under High-Temperature and Anaerobic Conditions
by Xiulun Shen, Sijia He, Yutaro Takaya, Tomoyoshi Yakata, Kotaro Yoshida and Hajime Kobayashi
Microorganisms 2025, 13(5), 1102; https://doi.org/10.3390/microorganisms13051102 - 10 May 2025
Viewed by 611
Abstract
Microbially induced carbonate precipitation (MICP) is the precipitation of CaCO3 crystals, induced by microbial metabolic activities such as ureolysis. Various applications of MICP have been proposed as innovative biocementation techniques. This study aimed to verify the feasibility of ureolysis-driven MICP applications in [...] Read more.
Microbially induced carbonate precipitation (MICP) is the precipitation of CaCO3 crystals, induced by microbial metabolic activities such as ureolysis. Various applications of MICP have been proposed as innovative biocementation techniques. This study aimed to verify the feasibility of ureolysis-driven MICP applications in deep-subsurface environments (e.g., enhanced oil recovery and geological carbon sequestration). To this end, we screened sludge collected from a high-temperature anaerobic digester for facultatively anaerobic thermophilic bacteria possessing ureolytic activity. Then, we examined the ureolysis-driven MICP using a representative isolate, Bacillus haynesii strain SK1, under aerobic, anoxic, and strict anaerobic conditions at 30 °C, 40 °C, and 50 °C. All cultures showed ureolysis and the formation of insoluble precipitates. Fourier transform infrared spectroscopy analysis revealed precipitates comprising CaCO3 at 30 °C, 40 °C, and 50 °C under aerobic conditions but only at 50 °C under anoxic and strict anaerobic conditions, suggesting efficient MICP at 50 °C. Interestingly, an X-ray diffraction analysis indicated that calcium carbonate crystals that were produced under aerobic conditions were in the form of calcite, while those that were produced under anoxic and strict anaerobic conditions at 50 °C were mostly in the form of vaterite. Thus, we demonstrated ureolysis-driven MICP under high-temperature and O2-depletion conditions, suggesting the potential of MICP applications in deep-subsurface environments. Full article
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26 pages, 16209 KiB  
Article
A Bacteria Acclimation Technology Based on Nitrogen Source Regulation and Its Application in the Reinforcement of Island and Reef Slopes
by Xin Chen, Ziyu Wang, Liang Cao, Peng Cao, Shuyue Liu, Yu Xie and Yingqi Xie
J. Mar. Sci. Eng. 2025, 13(5), 848; https://doi.org/10.3390/jmse13050848 - 24 Apr 2025
Viewed by 579
Abstract
Microbially Induced Calcium Carbonate Precipitation (MICP) technology has garnered significant attention in geotechnical engineering and environmental remediation due to its environmentally friendly and cost-effective advantages. However, the current MICP technology faces challenges in practical engineering applications, particularly the prolonged cementation time, which makes [...] Read more.
Microbially Induced Calcium Carbonate Precipitation (MICP) technology has garnered significant attention in geotechnical engineering and environmental remediation due to its environmentally friendly and cost-effective advantages. However, the current MICP technology faces challenges in practical engineering applications, particularly the prolonged cementation time, which makes it difficult to meet the requirements for coastal slope reinforcement. Therefore, this study designed novel cultivation conditions for Sporosarcina pasteurii by regulating external nitrogen source concentration and evaluated its environmental adaptability by measuring OD600, urease activity, and bacterial length. By monitoring the changes in Ca2+ concentration, pH, and precipitation rate over time during the mineralization process, rapid cementation under MICP conditions was achieved. The engineering applicability of this approach in slope reinforcement was comprehensively assessed through simulated on-site scouring and penetration tests. The reinforcement mechanism and the microstructure of the cementation under novel cultivation conditions were analyzed using scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), and X-ray diffraction (XRD). The results indicated that the activity of Sporosarcina pasteurii in the modified NH4-YE medium significantly improved in freshwater environments, and the MICP mineralization reaction was rapid, completing within 4 h. The primary crystal form of the generated precipitate was rhombohedral calcite, which formed a tightly bonded microstructure with calcareous sand, achieving a maximum reinforcement strength of 13.61 MPa. The penetration strength increased by at least 20%, and the precipitation rate improved by at least 2-fold. The scouring morphology remained essentially unchanged within 6 h. The findings of this study provide foundational and theoretical data for the application of MICP reinforcement technology to coastal calcareous sand models. Full article
(This article belongs to the Special Issue Marine Geotechnical Applications in Marine Structures)
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23 pages, 7900 KiB  
Article
Microbial Culture Condition Optimization and Fiber Reinforcement on Microbial-Induced Carbonate Precipitation for Soil Stabilization
by Changjun Wang, Xiaoxiao Li, Jianjun Zhu, Wenzhu Wei, Xinran Qu, Ling Wang, Ninghui Sun and Lei Zhang
Sustainability 2025, 17(7), 3101; https://doi.org/10.3390/su17073101 - 31 Mar 2025
Viewed by 829
Abstract
Traditional soil stabilization methods, including cement and chemical grouting, are energy-intensive and environmentally harmful. Microbial-induced carbonate precipitation (MICP) technology offers a sustainable alternative by utilizing microorganisms to precipitate calcium carbonate, binding soil particles to improve mechanical properties. However, the application of MICP technology [...] Read more.
Traditional soil stabilization methods, including cement and chemical grouting, are energy-intensive and environmentally harmful. Microbial-induced carbonate precipitation (MICP) technology offers a sustainable alternative by utilizing microorganisms to precipitate calcium carbonate, binding soil particles to improve mechanical properties. However, the application of MICP technology in soil stabilization still faces certain challenges. First, the mineralization efficiency of microorganisms needs to be improved to optimize the uniformity and stability of carbonate precipitation, thereby enhancing the effectiveness of soil stabilization. Second, MICP-treated soil generally exhibits high fracture brittleness, which may limit its practical engineering applications. Therefore, improving microbial mineralization efficiency and enhancing the ductility and overall integrity of stabilized soil remain key issues that need to be addressed for the broader application of MICP technology. This study addresses these challenges by optimizing microbial culture conditions and incorporating polyethylene fiber reinforcement. The experiments utilized sandy soil and polyethylene fibers, with Bacillus pasteurii as the microbial strain. The overall experimental process included microbial cultivation, specimen solidification, and performance testing. Optimization experiments for microbial culture conditions indicated that the optimal urea concentration was 0.5 mol/L and the optimal pH was 9, significantly enhancing microbial growth and urease activity, thereby improving calcium carbonate production efficiency. Specimens with different fiber contents (0% to 1%) were prepared using a stepwise intermittent grouting technique to form cylindrical samples. Performance test results indicated that at a fiber content of 0.6%, the unconfined compressive strength (UCS) increased by 80%, while at a fiber content of 0.4%, the permeability coefficient reached its minimum value (5.83 × 10−5 cm/s). Furthermore, microscopic analyses, including X-ray diffraction (XRD) and scanning electron microscopy with energy-dispersive spectroscopy (SEM–EDS), revealed the synergistic effect between calcite precipitation and fiber reinforcement. The combined use of MICP and fiber reinforcement presents an eco-friendly and efficient strategy for soil stabilization, with significant potential for geotechnical engineering applications. Full article
(This article belongs to the Section Soil Conservation and Sustainability)
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27 pages, 4124 KiB  
Article
Enhanced MICP for Soil Improvement and Heavy Metal Remediation: Insights from Landfill Leachate-Derived Ureolytic Bacterial Consortium
by Armstrong Ighodalo Omoregie, Fock-Kui Kan, Hazlami Fikri Basri, Muhammad Oliver Ensor Silini and Adharsh Rajasekar
Microorganisms 2025, 13(1), 174; https://doi.org/10.3390/microorganisms13010174 - 15 Jan 2025
Cited by 5 | Viewed by 2677
Abstract
This study investigates the potential of microbial-induced calcium carbonate precipitation (MICP) for soil stabilization and heavy metal immobilization, utilizing landfill leachate-derived ureolytic consortium. Experimental conditions identified yeast extract-based media as most effective for bacterial growth, urease activity, and calcite formation compared to nutrient [...] Read more.
This study investigates the potential of microbial-induced calcium carbonate precipitation (MICP) for soil stabilization and heavy metal immobilization, utilizing landfill leachate-derived ureolytic consortium. Experimental conditions identified yeast extract-based media as most effective for bacterial growth, urease activity, and calcite formation compared to nutrient broth and brown sugar media. Optimal MICP conditions, at pH 8–9 and 30 °C, supported the most efficient biomineralization. The process facilitated the removal of Cd2+ (99.10%) and Ni2+ (78.33%) while producing stable calcite crystals that enhanced soil strength. Thermal analyses (thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC)) confirmed the successful production of CaCO3 and its role in improving soil stability. DSC analysis revealed endothermic and exothermic peaks, including a significant exothermic peak at 444 °C, corresponding to the thermal decomposition of CaCO3 into CO2 and CaO, confirming calcite formation. TGA results showed steady weight loss, consistent with the breakdown of CaCO3, supporting the formation of stable carbonates. The MICP treatment significantly increased soil strength, with the highest surface strength observed at 440 psi, correlating with the highest CaCO3 content (18.83%). These findings underscore the effectiveness of MICP in soil stabilization, pollutant removal, and improving geotechnical properties. Full article
(This article belongs to the Topic Environmental Bioengineering and Geomicrobiology)
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19 pages, 11104 KiB  
Article
Microbially Induced Calcite Precipitation (MICP) Improved Drilling Fluid Optimization for Gravel Stratum
by Rui Pan, Zhou Shu, Yumin Chen, Xiaobing Sha, Xinquan Zhang and Yi Han
Processes 2025, 13(1), 162; https://doi.org/10.3390/pr13010162 - 9 Jan 2025
Viewed by 1021
Abstract
During the exploration of the gravel stratum, incidents such as wellbore leakage, stuck drilling, and unstable wellbore walls frequently occur. These issues lead to diminished drilling efficiency and prolonged construction timelines, ultimately adversely affecting the core recovery rate, resulting in a significant waste [...] Read more.
During the exploration of the gravel stratum, incidents such as wellbore leakage, stuck drilling, and unstable wellbore walls frequently occur. These issues lead to diminished drilling efficiency and prolonged construction timelines, ultimately adversely affecting the core recovery rate, resulting in a significant waste of manpower and material resources. To address the issue of hole collapse during drilling, the microbially induced calcite carbonate precipitation (MICP) technique was employed to enhance the properties of bentonite mud drilling fluids. This study analyzed the effects of three factors, i.e., bentonite, biological solution, and barite powder, on the bentonite mud bio-cementation effectiveness through an orthogonal experiment and response surface methodology (RSM). The biological mechanism was examined using scanning electron microscopy (SEM). The experimental results indicated that optimal formulation was achieved when the mass fraction of bentonite was 13.96%, the biological solution comprised 0.6% xanthan gum and 0.4% carboxymethyl cellulose, and the mass fraction of barite was 25%. This research explores the application potential of MICP in enhancing the rheological properties of bentonite mud drilling fluids, which provides new insights and technical references for optimizing their performance. Full article
(This article belongs to the Section Chemical Processes and Systems)
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17 pages, 4090 KiB  
Article
Crack Sealing in Concrete with Biogrout: Sustainable Approach to Enhancing Mechanical Strength and Water Resistance
by Jian Wang, Shengjie Ji, Shuguang Huang, Zihang Jiang, Siqi Wang, Huaiqi Zhang, Zijian Wang and Junfei Zhang
Materials 2024, 17(24), 6283; https://doi.org/10.3390/ma17246283 - 23 Dec 2024
Cited by 3 | Viewed by 1225
Abstract
Concrete, as the most widely used construction material globally, is prone to cracking under the influence of external factors such as mechanical loads, temperature fluctuations, chemical corrosion, and freeze–thaw cycles. Traditional concrete crack repair methods, such as epoxy resins and polymer mortars, often [...] Read more.
Concrete, as the most widely used construction material globally, is prone to cracking under the influence of external factors such as mechanical loads, temperature fluctuations, chemical corrosion, and freeze–thaw cycles. Traditional concrete crack repair methods, such as epoxy resins and polymer mortars, often suffer from a limited permeability, poor compatibility with substrates, and insufficient long-term durability. Microbial biogrouting technology, leveraging microbial-induced calcium carbonate precipitation (MICP), has emerged as a promising alternative for crack sealing. This study aimed to explore the potential of Bacillus pasteurii for repairing concrete cracks to enhance compressive strength and permeability performance post-repair. Experiments were conducted to evaluate the bacterial growth cycle and urease activity under varying concentrations of Ca2+. The results indicated that the optimal time for crack repair occurred 24–36 h after bacterial cultivation. Additionally, the study revealed an inhibitory effect of high calcium ion concentrations on urease activity, with the optimal concentration identified as 1 mol/L. Compressive strength and water absorption tests were performed on repaired concrete specimens. The compressive strength of specimens with cracks of varying dimensions improved by 4.01–11.4% post-repair, with the highest improvement observed for specimens with 1 mm wide and 10 mm deep cracks, reaching an increase of 11.4%. In the water absorption tests conducted over 24 h, the average mass water absorption rate decreased by 31.36% for specimens with 0.5 mm cracks, 29.06% for 1 mm cracks, 27.9% for 2 mm cracks, and 28.2% for 3 mm cracks. X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses confirmed the formation of dense calcium carbonate precipitates, with the SEM–EDS results identifying calcite and vaterite as the predominant self-healing products. This study underscores the potential of MICP-based microbial biogrouting as a sustainable and effective solution for enhancing the mechanical and durability properties of repaired concrete. Full article
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22 pages, 9844 KiB  
Article
Numerical Investigation of Heterogeneous Calcite Distributions in MICP Processes
by Lingxiang Wang, Yajie Chu, Xuerui Wang, Pengzhi Pan and Dianlei Feng
Minerals 2024, 14(10), 999; https://doi.org/10.3390/min14100999 - 30 Sep 2024
Cited by 2 | Viewed by 1116
Abstract
Microbially induced calcite precipitation (MICP) is a sustainable and environmentally friendly technology with applications in soil stabilization, concrete crack repair, and wastewater treatment. This study presents an improved Darcy-scale numerical model to simulate the MICP processes in heterogeneous porous media. It focuses on [...] Read more.
Microbially induced calcite precipitation (MICP) is a sustainable and environmentally friendly technology with applications in soil stabilization, concrete crack repair, and wastewater treatment. This study presents an improved Darcy-scale numerical model to simulate the MICP processes in heterogeneous porous media. It focuses on the effects of porosity heterogeneity, characterized by average porosity and correlation length, as well as injection strategies. Both average porosity and correlation length are critical factors influencing mass transport and calcite distribution during MICP treatment. An increase in average porosity leads to significant reductions in transport distance and total calcite mass. Notably, in the case of low averaged porosity, a larger correlation length results in more heterogeneous calcite distributions. However, there exists an upper threshold value of the initial averaged porosity (ϕ0=0.45) above which the heterogeneity of the calcite does not present clear dependence on the correlation length. Additionally, injection strategies significantly impact the consolidation effects. Compared to continuous injection, using the phased injection strategy can greatly improve the precipitated calcite area and mass due to its high utility and the efficiency of reactants. Full article
(This article belongs to the Special Issue Mineral Dissolution and Precipitation in Geologic Porous Media)
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20 pages, 15520 KiB  
Article
Single-Particle Crushing Test of Coated Calcareous Sand Based on MICP
by Shuyue Zhu, Linxian Gong, Zhazha Hu, Yan Xu, Yuanyuan He and Yunyi Long
Materials 2024, 17(19), 4690; https://doi.org/10.3390/ma17194690 - 24 Sep 2024
Cited by 3 | Viewed by 1188
Abstract
Calcareous sand is a crucial construction material for island and reef development and reinforcing it using Microbially Induced Calcite Precipitation (MICP) technology is a promising new method. This study employed 3D scanning technology to assess changes in the particle size and morphology of [...] Read more.
Calcareous sand is a crucial construction material for island and reef development and reinforcing it using Microbially Induced Calcite Precipitation (MICP) technology is a promising new method. This study employed 3D scanning technology to assess changes in the particle size and morphology of MICP-treated, coated calcareous sand particles. Single-particle crushing tests were conducted to analyze their crushing strength, crushing energy, crushing modes, and fragment fractal dimensions. The results indicated that MICP treatment significantly increased particle size, surface area, and volume, while reducing flatness. At a cementation solution concentration of 1 mol/L, both crushing strength and crushing energy were optimized. The coated particles exhibited three crushing modes: explosive crushing, mixed crushing, and splitting crushing. Thicker coatings led to a tendency for particles to break into larger fragments through the mixed and splitting crushing modes. Fractal analysis revealed that coating thickness directly affects the local crushing characteristics of the particles. Full article
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18 pages, 12388 KiB  
Article
Factors Affecting the Physical Properties of Microbial Induced Calcium Carbonate Precipitation (MICP) Enhanced Recycled Aggregates
by Jin Zhang, Cong Wang and Zhipeng Wang
Buildings 2024, 14(9), 2851; https://doi.org/10.3390/buildings14092851 - 10 Sep 2024
Cited by 6 | Viewed by 2287
Abstract
Microbial-induced calcium carbonate precipitation (MICP) can enhance the physical properties of recycled aggregates. Compared to traditional technologies, MICP offers environmental benefits and produces no pollution. However, its mineralization efficacy is significantly influenced by the process parameters. To investigate this, an MICP mineralization test [...] Read more.
Microbial-induced calcium carbonate precipitation (MICP) can enhance the physical properties of recycled aggregates. Compared to traditional technologies, MICP offers environmental benefits and produces no pollution. However, its mineralization efficacy is significantly influenced by the process parameters. To investigate this, an MICP mineralization test was conducted by manipulating various process parameters throughout the mineralization process. The water absorption rate, apparent density, and calcium carbonate content of the mineralized recycled aggregates were assessed to discern the impact of these parameters on the mineralization outcome. Further analysis using techniques such as thermogravimetric analysis (TG), X-ray diffraction (XRD), nuclear magnetic resonance (NMR), and scanning electron microscopy (SEM) were employed to elucidate the mineralization mechanism of the recycled aggregates at a micro-level. The findings indicated that the MICP treatment induced bacteria to precipitate CaCO3, forming calcite crystalline CaCO3 within the pores and microcracks. This led to a denser interfacial transition zone and, consequently, improved the physical properties of the recycled aggregates. Optimal mineralization was achieved when the bacterial solution concentration was 1.4, the temperature and pH were 35 °C and 9, respectively, and the urea concentration, Ca+ concentration, and mineralization time were 0.5 mol/L, 0.5 mol/L, and 7 days, respectively. Under these conditions, the mineralized recycled aggregate exhibited a 16.07% reduction in water absorption, a 1.07% increase in apparent density, and a 2.28% change in mass. Full article
(This article belongs to the Topic Sustainable Building Materials)
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11 pages, 3812 KiB  
Article
The Effect of Bacteria-to-Calcium Ratio on Microbial-Induced Carbonate Precipitation (MICP) under Different Sequences of Calcium-Source Introduction
by Teng Zhao, Hongxiu Du and Ruihua Shang
Materials 2024, 17(8), 1881; https://doi.org/10.3390/ma17081881 - 19 Apr 2024
Cited by 7 | Viewed by 1500
Abstract
To explore the effects of the introduction order of calcium sources and the bacteria-to-calcium ratio on the microbially induced calcium carbonate precipitation (MICP) product CaCO3 and to achieve the regulation of CaCO3 crystal morphology, the mineralisation products of MICP were compared [...] Read more.
To explore the effects of the introduction order of calcium sources and the bacteria-to-calcium ratio on the microbially induced calcium carbonate precipitation (MICP) product CaCO3 and to achieve the regulation of CaCO3 crystal morphology, the mineralisation products of MICP were compared after combining bacteria and calcium at ratios of 1/9, 2/9, 3/9, 4/9, 5/9, and 6/9. A bacterial solution was combined with a urea solution in two calcium addition modes: calcium-first and calcium-later modes. Finally, under the calcium-first addition method, the output of high-purity vaterite-type CaCO3 was achieved at bacteria-to-calcium ratios of 2/9 and 3/9; under the calcium-later addition method, the output of calcite-type CaCO3 could be stabilised, and the change in the bacteria-to-calcium ratio did not have much effect on its crystalline shape. Full article
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