Development of a 2-phase bio-additive for self-healing cement-based materials

Microracks are one of the main reasons for a decrease in service life in concrete structures. Recent research in the field suggested that it might be possible to develop a smart cement-based material that is capable of remediate cracks by triggering calcium carbonate (CaCO3) precipitation. Throughout the literature, studies showed that there could be various alternatives to incorporate the microorganisms (bacterial cells) where the cells could remain viable for a defined period and self-heal the cracks resultign with a decrease in permeability. These methods often involve encapsulation of bacterial cells in organic or synthetic capsules before incorporation to the mix. This study aims to develop a sustainable and cost-efficient bio-based addive to trigger self-healing in cement-based composites.To achieve this goal, Sporosarcina pasteurii cells were immobilized on diatomaceous earth (DE) and pumice. At the end of the 28th day of mixing, the samples were cracked using a servo hydraulic displacement-controlled device. Two different curing regimes, water and nutrient medium, were applied after crack formation. Self-healing was achieved in samples containing bio-based additive regardless of the curing regime. In average, 80% crack sealing was attained after 2 weeks of curing. There was a significant decrease in water absorption capacity upon crack healing.