In Bio‐Based Self‐Healing Concrete: Effect of Nutrient Components of the Media on Mechanical Properties and Environmentally Friendly Concrete Development

More durable and eco‐friendly alternatives to concrete are needed to meet the growing global demand for this material. About 7% of all human‐caused CO 2 emissions come from cement production. Integrating bacteria into concrete can prolong its lifespan, improve durability, and promote the sustainability of the concrete. Traditional crack repair methods, such as epoxy injection, grouting, drilling, plugging, and gravity filling, are time‐consuming, require additional maintenance, and have a negative environmental impact. The objective of the present study was to evaluate bacteria as self‐healing agents by investigating their capacity to seal cracks via calcium carbonate (CaCO 3 ) production, as well as the influence of organic nutrient media, particularly the content of carbon and nitrogen. The impact of bacteria and nutrient media was evaluated by fabricating three concrete variants and curing them in four distinct environments: water, nutrient broth, bacteria‐nutrient solution, and bacteria‐sprayed control specimens. The properties, including setting time, strength, acid and sulfate resistance, chemical composition, bacterial viability, and microstructure (analyzed via scanning electron microscopy [SEM]/energy dispersive X‐ray [EDX]), were evaluated at various ages over time. The results demonstrate that the organic nutrient medium hurts the setting, hydration, and mechanical properties of the concrete, whereas the bacteria‐infused mixtures remain unaffected. After 28 days of curing, bacterial specimens treated with bacteria‐nutrient solution exhibited strength enhancements of 32.5% (compressive), 29.78% (flexural), and 20.3% (tensile), while media admixture‐treated concrete demonstrated strength declines of 38.4%, 34%, and 42.4%, respectively, compared to the control concrete. Bacteria admixture‐treated (BAT) concrete and bacteria‐spray‐treated concrete exhibited superior resistance to H 2 SO 4 and MgSO 4 compared to the control concrete. Additionally, bacterially treated samples showed higher levels of carbon, nitrogen, and CaCO 3 , along with effective repair of 3 mm cracks. Bacterial spores remained inactive in small pores (<1 µm) until stimulated by cracking, indicating significant potential for self‐healing concrete. This suggests that using bacterial spores as a self‐sealing agent holds enormous potential.