In the field of construction materials, concrete is widely used globally but is prone to cracking, which leads to reduced mechanical strength and durability, and high repair costs. Traditional repair methods (e.g., polymers, supplementary cementitious materials) have limitations such as high environmental impact, poor interfacial bonding, and on-site application difficulties.
Microorganism-based self-healing concrete, which uses bacteria to induce calcite precipitation for crack sealing, has emerged as a promising solution. However, existing studies lack systematic reviews of its mechanical properties (compressive, tensile, flexural strength) and durability performance (carbonation, chloride resistance, freeze-thaw resistance), especially when combined with supplementary cementitious materials (SCMs) and fibers, hindering its standardized application.
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Therefore, a research team from the Department of Civil Engineering at the Indian Institute of Technology Delhi has conducted a study entitled “Bibliographic Survey and Comprehensive Review on Mechanical and Durability Properties of Microorganism Based Self-Healing Concrete”.
Developing countries
This study first conducted a bibliographic analysis using VOSViewer and Scopus data (589 documents), revealing that developing countries contribute more to this field in recent years, with Construction and Building Materials publishing 36.6% of relevant documents. Subsequently, a comprehensive review was carried out:
- Bacteria application and biomineralization: Bacteria (e.g., Bacillus subtilis, Bacillus sphaericus) are added via direct mixing, surface spraying, or encapsulation (carriers include expanded clay, natural fibers). Biomineralization occurs through autotrophic (e.g., photosynthesis) or heterotrophic (e.g., ureolysis, denitrification) pathways, generating CaCO₃ to seal cracks (up to 0.46 mm, 4x more effective than autogenous healing).
- Mechanical properties: The optimal bacterial concentration is 10⁵–10⁸ cfu/mL. Bacillus sphaericusshows the best performance, increasing compressive strength by up to 42% and flexural strength by 50–70%. Combining with SCMs (silica fume, fly ash) or fibers (coir, steel fibers) further enhances strength—e.g., 10% silica fume + bacteria increases compressive strength by 12%, and steel fibers improve flexural strength by 50%.
- Durability performance:
Carbonation resistance: Bacteria reduce carbonation depth by 40–50% via pore filling, but acidic curing media (urea-lactate) weaken this effect.
Permeability: Calcite precipitation reduces water absorption by up to 60% and chloride ion penetration (RCPT charge passed reduced by 57%), with most bacterial concrete falling in the “very low-low” permeability range.
Freeze-thaw resistance: Bacterial mortar retains 98% of initial weight after 300 freeze-thaw cycles (vs. 69% for control), with expansion reduced by 44–73%.
Material characterization: X-ray computed tomography (XCT) reveals that bacteria-encapsulated hydrogel systems generate 2.2% volume precipitation (vs. 0.21% for control), confirming effective crack sealing.
The paper “Bibliographic survey and comprehensive review on mechanical and durability properties of microorganism based self-healing concrete” is authored by Md Marghoobul Haque, Kunal M. Shelote, Namrata Singh, and Supratic Gupta. The full text is available at: https://doi.org/10.1007/s11709-024-1098-7.
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