What if the concrete in buildings and bridges could heal itself like a wound healing on skin? That’s the idea behind new research from Dr. Congrui Grace Jin, whose recent study explores a microbe-powered, self-healing concrete system. Concrete is everywhere in our daily lives—from buildings to roads—but it tends to crack with time and stress. These cracks, even the tiny ones, can let water and air inside, eventually causing rust and weakening the steel hidden within. That’s risky and expensive to fix, especially on bridges and highways.
For many years, scientists have tried using bacteria to repair these cracks automatically. But most of these methods need an external supply of nutrients to keep the bacteria working. Jin points out this major hurdle, saying, “Microbe-mediated self-healing concrete has been extensively investigated for more than three decades, but it still suffers from one important limitation—none of the current self-healing approaches are fully autonomous since they require an external supply of nutrients for the healing agents to continuously produce repair materials.”
Her solution takes cues from nature by recreating lichens, which are simple organisms made of fungi and cyanobacteria that survive on nothing more than air, sunlight, and water. Jin’s team designed a synthetic version using diazotrophic cyanobacteria, which absorb carbon dioxide and nitrogen from the air, and filamentous fungi, which help collect calcium ions and make calcium carbonate (CaCO₃), a mineral that can fill in concrete cracks.
They tested three microbe pairings: Trichoderma reesei with Anabaena inaequalis, T. reesei with Nostoc punctiforme, and T. reesei with both A. inaequalis and N. punctiforme. All three combinations grew well in a lab setup that had only air and light—no added nutrients. To see how well the microbes performed, the team used five methods: optical density to check light absorption, dry weight of biomass, resazurin assay for metabolic activity, fungal plating on selective media, and a phycocyanin test to check cyanobacteria health.
Results showed that the paired microbes were healthier and more productive than when grown alone. They were able to form CaCO₃ even in concrete samples, pointing to real-world potential. What makes this approach stand out is its ability to repair cracks without human assistance, which could one day reduce the need for expensive manual inspection and maintenance.
Jin is also working with social scientists at Texas A&M University to understand how the public feels about using "living" organisms in buildings, and to explore ethical and legal questions involved. The research, funded by DARPA’s Young Faculty Award program, brings biology and engineering together to solve a practical problem that affects millions of people.
Source: Texas A&M University, ScienceDirect
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