Background:High-strength concrete (M45) is widely used in structural applications but remains susceptible to microcracking, affecting durability and service life. Bacterial self-healing using Bacillus subtilis offers a potential solution through microbiologically induced calcium carbonate precipitation. Methods:An experimental laboratory study was conducted using M45 concrete with and without bacterial incorporation. Encapsulated Bacillus subtilis with calcium lactate was added to the test group. Compressive, flexural, and split tensile strengths were evaluated at 7, 21, and 28 days. Statistical analysis using one-way ANOVA was performed. Results:Bacterial concrete demonstrated higher strength across all parameters. At 28 days, compressive strength increased from 47.6 MPa to 53.5 MPa (12.4%), flexural strength from 7.2 MPa to 8.1 MPa (12.5%), and split tensile strength from 4.1 MPa to 4.6 MPa (12.2%). All differences were statistically significant (p < 0.05). Conclusion:Incorporation of Bacillus subtilis significantly improved the mechanical properties of M45 concrete through calcite precipitation and matrix densification. Recommendation:Further studies are required to evaluate long-term durability, field performance, and cost optimization for large-scale applications.

Life-cycle-driven cleaner production of bacterial concrete using agro-waste-derived nano-silica for sustainable building applications

Concrete is a major contributor to carbon emissions worldwide. In response to this climate impact, scientists are actively working to develop more sustainable alternatives to traditional concrete. One potential alternative is bio-enzyme-based concrete, or BBE, made using Bacillus aerophilus from fermented soybeans, watermelons, and palm jaggery solution. BBE transform carbon dioxide into crystals of calcium carbonate, allowing concrete to heal itself when cracked and decreasing emissions in the process. BBE-mortar has better mechanical properties than Portland cement mortar and is also cheaper and more sustainable. Cocci-shaped bacterial spores are also evident in SEM images taken at day 28 where the bacteria initiate the healing of the cracks. These bacteria reduce levels of CO2 in the process as they precipitate calcium and barium deposits, resulting in negative carbon emissions during construction. In fact, EDS analysis shows high levels of barium, calcium, and iron in the bacterial concrete, which absorb CO2 from the atmosphere with compounds to form precipitates such as BaCO3, CaCO3, and FeCO3. Among other advancements, this technology renders concrete “self-healing”, massively cuts carbon emissions, and allows construction to have a lighter ecological footprint – potentially revolutionizing construction for sustainability.

Bacteria-based self-healing concrete is extensively shown to improve strength and durability; yet, the mechanistic relationship among microbial activity, damage progression, and transport resistance is still ambiguous. This study examines the interrelated mechanical and transport properties of concrete that incorporates Bacillus subtilis by directly substituting mixing water. Concrete mixtures with 0%, 5%, and 10% bacterial solution were assessed for compressive strength, complete stress-strain response, split tensile strength, flexural toughness, fast chloride ion penetration, and capillary sorptivity. X-ray diffraction was employed for microstructural validation. Results indicate a dose-dependent shift from brittle to quasi-ductile behavior, marked by augmented strain capacity, postponed crack localization, and improved post-cracking energy absorption. The mechanical alterations resulted in substantial decreases in chloride ion penetrability (up to 57%) and capillary sorptivity (up to 60%), signifying a drop in crack-assisted transport. X-ray diffraction verified the production of calcite resulting from microbial-induced calcium carbonate precipitation. The results indicate that the improvement in durability of bacterial concrete is attributable not only to pore filling but also to altered damage mechanisms that diminish the connectedness of transport channels, underscoring the potential of Bacillus subtilis as a bio-admixture for resilient structural concrete.

Experimental Investigation and Characterization Studies on Coconut Fibre Reinforced Bacterial Concrete Using Bacillus Subtilis

Experimental Investigation of Multi-Strain Bacterial Concrete: Self-Healing Efficiency, Strength, and Sorptivity under Varied Curing Conditions

Concrete is a major building material. This study looked at Bacterial Concrete (BC), which is created by mixing a bacterial solution with a cell concentration of 10⁷ CFU/ml. This amount is equivalent to 8% of the cement weight and helps to improve the performance in marine environments. Adding bacterial culture significantly enhanced the concrete’s mechanical properties, durability, and self-healing ability. As a result, it showed better compressive strength than regular concrete. The major aim of this study is to see how the bacterial concrete could reduce the harmful effects of environmental stressors on marine structures. It also evaluated the economic feasibility and sustainability of Bacterial Concrete before use. During testing, Bacterial concrete beams were soaked in seawater for 365 days and showed no rebar corrosion, which is a common problem in normal concrete. Durability tests included water absorption, sorptivity, bulk diffusion, and sulphate resistance. Rice husk ash is utilized for the purpose of strengthening the M40-grade concrete, while adding 5 to 10 percent corn starch improved flowability and the setting time without losing strength. Furthermore, 0.5 percent silica fume is included to boost strength and durability. The study wraps up by discussing sustainability challenges and offering insights to promote the use of bacterial concrete in strong and lasting marine applications.

Embedment of the combination of nutrients for evaluating the mechanical strength and microstructural properties of an aerobic non-ureolytic self-healing bacterial concrete

This study investigates the effects of agro-waste-based capsules made from grape seeds and cherry pits on the physical, mechanical, thermal and self-healing properties of concrete. Capsule-containing mixtures were compared with a reference concrete after 28 days of water curing using both standardized and non-standardized testing methods. Capsule incorporation reduced workability by up to 91% and altered air content depending on capsule type, increasing it by 47% for grape seed capsules and decreasing it by 65% for cherry pit capsules. Fresh concrete density was reduced by 5.5% and 6.8% for grape seed and cherry pit capsules, respectively, while hardened concrete density decreased by 11% and 9%, implying lighter structures with improved seismic resistance. Compressive strength decreased by 49% for grape seed capsules and 27% for cherry pit capsules. Thermal conductivity was reduced by 32% and 22%, respectively, indicating improved energy efficiency. Concrete with grape seed capsules showed freeze–thaw performance comparable to the reference concrete after 112 cycles, whereas concrete with cherry pit capsules exhibited superior dynamic modulus behavior, suggesting continuous crack healing, despite significant mass loss due to poor capsule–matrix bonding. SEM analysis showed no significant crack reduction, while EDS revealed calcium-rich areas in grape seed capsule concrete, indicating possible crack healing. Overall, agro-waste capsule concrete shows potential for improving seismic resistance and energy efficiency, although further research is required to clarify the self-healing effect.

Abstract Caracking is an inevitable phenomenon in concrete structures that significantly affects durability and service life by facilitating the ingress of aggressive agents. In recent years, self-healing concrete has emerged as a promising solution to address these challenges. This study investigates the mechanical performance, durability characteristics, and crack-healing efficiency of bacterial concrete incorporating Bacillus subtilis. Bacterial concentrations of 10⁶, 10⁷, and 10⁸ CFU/ml were introduced into M30 grade concrete. Compressive strength, split tensile strength, ultrasonic pulse velocity (UPV), water absorption, sorptivity, and rapid chloride permeability tests (RCPT) were conducted. Controlled cracks were induced, and healing was monitored over 7, 14, and 28 days. The results demonstrate that bacterial concrete exhibits superior strength, reduced permeability, and effective crack healing compared to conventional concrete. The mix containing 10⁸ CFU/ml showed optimum performance, achieving up to 90% crack-healing efficiency. The findings confirm that bacterial concrete is a sustainable and durable alternative for modern infrastructure applications. Keywords: Bacterial concrete, Bacillus subtilis, self-healing concrete, MICP, durability, crack healing.

ABSTRACT This study explores the mechanical properties and self‐healing capabilities of bacterial concrete using Bacillus species in M25 grade concrete. Various bacterial concentrations 0%, 5%, 10%, and 15% were incorporated to assess their influence on compressive, flexural, and split tensile strengths, as well as crack‐healing behavior. The selected bacteria were capable of inducing microbial calcium carbonate precipitation (MICP), promoting internal crack sealing. Strength tests and self‐healing evaluations were conducted over a 28‐day period. The results indicated that a 10% bacterial concentration yielded the most effective performance, with a 20%–30% increase in strength compared to control specimens. Crack closure efficiency reached up to 23.80% due to visible microcrack sealing. However, concentrations above 10% showed diminished returns, suggesting a saturation point beyond which bacterial effectiveness declines. Microstructural analyses using Scanning Electron Microscopy (SEM) and X‐Ray Diffraction (XRD) confirmed the formation of CaCO 3 within the concrete matrix. Overall, the findings support bacterial concrete as a promising, sustainable solution for improving structural durability and minimizing maintenance.

Assessment of strength and self-healing properties of bacterial concrete using machine learning techniques and microstructural characterization

Effect of incorporation of fly ash on the performance of Bacillus-based bacterial concrete

A multiphysics finite element framework for CO2-induced self-healing in bacterial concrete

This study investigates the durability enhancement of bacterial concrete incorporating microbial strains (Bacillus Licheniformis, Bacillus Flexus, Pseudomonas stutzeri, Escherichia coli, and Bacillus subtilis) through microbial-induced calcium carbonate precipitation (MICP). Various durability tests, including water absorption, RCPT, sulphate resistance, hydrochloric acid strength loss, sorptivity, and energy-dispersive X-ray analysis (EDAX), were conducted to evaluate the effectiveness of bacterial concrete. Bacterial concrete significantly reduces water absorption and chloride ion penetration, with Bacillus subtilis (M16) and Bacillus Flexus (M7) demonstrating the highest impermeability. Sulphate resistance analysis confirmed reduced weight loss before and after healing, highlighting microbial self-healing capabilities. Hydrochloric acid strength loss and sorptivity tests further validated improved acid resistance and reduced capillary absorption. EDAX analysis confirmed the formation of calcium carbonate, contributing to matrix densification and enhanced durability. Overall, microbial concrete exhibited superior resistance to environmental degradation, with Bacillus subtilis, Bacillus Flexus, and Bacillus Licheniformis at higher concentrations (106 cells/ml) providing the most significant improvements.Bacterial concrete showed increased workability and notable compressive, flexural, and split tensile strengths with Bacillus subtilis and Bacillus licheniformis at 10⁶ cells/mL,Bacterial concrete provide the best self-healing and strength recovery capability; SEM and XRD data revealed higher density and effective crack healing.Bacterial concrete is a sustainable material since it provides long-term durability by means of inherent self-healing systems.

This study investigates the durability and acid resistance of bacterial and conventional concrete under prolonged exposure to acidic environments. Concrete specimens were subjected to immersion in 5% H₂SO₄ and 5% HCl solutions for a period of 105 days, during which weight loss, compressive strength loss, Acid Durability Factor (ADF), and Acid Attack Factor (AAF) were evaluated. Bacterial concrete demonstrated superior performance compared to conventional concrete, showing significantly reduced weight loss and compressive strength degradation in both acid solutions.For ordinary grade concrete in H₂SO₄, bacterial concrete exhibited 12.55% less weight loss and 6.22% less strength loss than conventional concrete. Similarly, in standard grade concrete, bacterial concrete showed 18.57% less weight loss and 42.12% less strength loss. When immersed in HCl, bacterial concrete displayed a 22.5% reduction in weight loss and a 14.5% decrease in compressive strength loss compared to conventional concrete. The ADF and AAF values further confirmed bacterial concrete's enhanced resistance to acid attack, maintaining higher durability and lower corner damage over the exposure period.The findings underscore bacterial concrete's potential for applications in harsh acidic environments, providing improved durability, sustainability, and reduced maintenance costs. This study establishes bacterial concrete as a promising material for infrastructure in chemically aggressive conditions.

The potential for creating unique, environmentally friendly, and cost-effective concrete via biomineralization is discussed in this research. Cement, a necessary component of concrete, is expensive and emits between 8 and 10% of the world’s CO2 emissions. Researchers have significant effects to identify alternatives that can reduce the burden of high costs, excessive energy use, and environmental repercussions. Manufactured sand (M-sand) completely replaced fine aggregate, and cement was replaced with alternatives such as Alccofine (AF) and Silica Fume (SF). The percentage at which it can be substituted for cement is, however, somewhat small. The goal of this study is to create an environmentally friendly AF and SF concrete mix by incorporating bacteria with the highest possible cell concentration. To evaluate the mechanical properties, concrete samples were tested for flexural strength, split tensile strength, and compressive strength at 7, 14 and 28 days postcuring. The microstructural analysis of sustainable concrete was performed using scanning electron microscopy (SEM) techniques. It was determined that 10% alccofine and 15% silica fume by volume of cement in the binary cementitious system provided the best mechanical characteristics for bacterial concrete using Bacillus megaterium. Similarly manner in the ternary cementitious system, the highest gain in compressive strength is seen when 10% alccofine is substituted with 10% silica fume in the cement mixture. Calcium carbonate precipitation validated the enhanced properties of bacterial concrete. The microorganisms used in the concrete are non-toxic and environmentally being. Results indicate that using Bacillus megaterium alongside AF and SF helps to reduce cement usage, lessens carbon dioxide emissions, and makes concrete more environmentally friendly. Using Scanning Electron Microscopy (SEM), the calcite precipitations in bio-additive mixed ternary admixture blended concrete were confirmed. The proposed regression equations produced minimal errors when compared to the experimental results, thus providing accurate and effective predictions of the flexural, split, and compressive strengths. The strength properties of these blends were validated through SEM studies.

This study investigates the influence of Bacillus subtilis bacteria on the strength and durability properties of M30 concrete with and without silica fume. The experimental study was conducted on four concrete mix series: conventional concrete (B1), conventional concrete with silica fume (B2), bacterial concrete without any admixtures (B3), and bacterial concrete with silica fume (B4). Silica fume was incorporated at replacement levels of 5% and 10% by weight of cement for the B2 and B4 mix series to evaluate its effect on bacterial activity and concrete performance. The study measured compressive strength, split tensile strength, and water absorption to assess mechanical and durability properties. Results reveal that bacterial concrete (B3 and B4) exhibits improved strength and durability compared to conventional concrete (B1 and B2). Furthermore, silica fume enhances the performance of bacterial concrete due to its pozzolanic action, which refines the microstructure and provides additional nucleation sites for calcium carbonate precipitation by Bacillus subtilis. Among all mixes, B4 with 10% silica fume achieved the highest strength and durability, demonstrating the synergistic effect of bacteria and silica fume. This research highlights the potential of bacterial concrete with silica fume as an innovative material for sustainable construction, offering improved mechanical performance and reduced permeability. Doi: 10.28991/CEJ-2025-011-05-013 Full Text: PDF

The effects of two different bacteria species on the strength, durability, and microstructure of self-healing concrete were compared. A new wild-type calcifying strain, extracted from agricultural soil of Gilan province, Iran, was used to prepare bacterial concrete. This strain was identified as Bacillus licheniformis. The self-healing capacity of this bacteria was evaluated at three different cell concentrations (1.5 × 108, 3.0 × 108, and 6.0 × 108 cells/ml), and its performance was compared with a standard strain of Sporosarcina pasteurii, which was prepared from the Iranian culture collection. Expanded perlite aggregate was used as a carrier. The mechanical properties and durability of mixtures at 7, 28, and 90 days were tested. The microstructure of some mixtures was also analyzed using field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray diffraction. The results indicated that the strength and permeability of the concrete were improved with the addition of bacteria. The mixture with 6 × 108 cells/ml B. licheniformis showed, respectively, 22% and 38% increases in compressive and tensile strength at 28 days. The FESEM and EDS results showed that the precipitation of calcite in concrete containing wild-type B. licheniformis was higher than that of the concrete containing S. pasteurii.

Abstract This study explores the impact of bacterial solutions on the performance and microstructural properties of concrete mixes. Incorporating up to 10% bacterial solution demonstrated significant improvements in the dynamic modulus of elasticity for both M40 and M20 grade concrete mixes, particularly when crushed stone sand was used in place of river sand. Microstructural analyses conducted after 28 days of curing confirmed the formation of calcite (calcium carbonate) in all bacterial concrete samples. Advanced investigations using X-ray diffraction and scanning electron microscopy revealed enhanced production of calcium silicate hydrate gel and non-expansive ettringite in bacterial concrete mixes containing 10% bacterial solution, leading to superior compressive strength. Energy-dispersive X-ray analysis further highlighted an increased calcium content, correlating with the presence of calcite. The findings underscore the potential of bacterial solutions to enhance the strength, durability, and longevity of concrete structures through improved microstructural composition. From the microstructural analysis, it has been derived that calcite contributed more to the improved strength and longevity of the bacterial concrete specimens.