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Nanoscale Characterization of Fungal-Induced CaCO3 Precipitation: Implications for Self-Healing Concrete

Summary

Researchers studied how fungi can help repair concrete cracks by producing calcium carbonate (similar to limestone) using advanced microscopy techniques. They found that three types of fungi all produced stable calcite crystals, which is good for making durable self-healing concrete. The study shows exactly how fungi work at the tiny nanoscale level to create these minerals, providing important information for developing better crack-healing concrete that could reduce environmental impact.

Background

Concrete cracks compromise structural integrity by exposing steel reinforcement to corrosion, shortening service life. Fungal-induced calcium carbonate (CaCO3) precipitation through urea hydrolysis offers a sustainable self-healing mechanism. However, current bulk-scale analytical methods lack the nanoscale spatial resolution to distinguish and map CaCO3 polymorphs effectively.

Objective

To characterize fungal CaCO3 polymorphs at the nanoscale using synchrotron-based scanning transmission X-ray microscopy (STXM) combined with near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. The study aims to understand fungal biomineralization mechanisms relevant to self-healing concrete applications.

Results

Calcite was identified as the predominant mineral phase precipitated by all fungi species, while aragonite and non-CO3-Ca species occurred as minor components. Nanoscale heterogeneity was observed, particularly in fungal species 2, with localized regions showing mixed CaCO3 phases influenced by local physicochemical and metabolic conditions. C NEXAFS spectra confirmed calcite-specific spectral features in calcite-rich regions.

Conclusion

STXM/NEXAFS successfully resolved complexities in fungal CaCO3 formation at the nanoscale, revealing calcite predominance suitable for durable self-healing applications. The observed heterogeneity highlights the need to optimize fungal growth conditions for field-scale concrete implementation. The study provides critical insights for developing fungal systems in self-healing concrete technologies.
  • Published in:ACS Applied Materials & Interfaces,
  • Study Type:Experimental Research,
  • Source: 10.1021/acsami.5c07137, PMID: 40542343
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