Self-healing cementitious materials based on bacteria and nutrients immobilized respectively

- Bacteria and nutrients were immobilized respectively into ceramsite to improve the self-healing effectiveness of cementitious materials.
- The depth of cracks before and after restoration was investigated by staining the section surfaces of specimens.
- The flexural strength of specimens after repairing was studied to characterize the repairing effectiveness of cracks.
- The precipitation formed in cracks was analyzed by SEM/EDS and XRD.

Small cracks in concrete may develop into large cracks to decrease service life of concrete structures. It is necessary to restrict the development of early age small cracks promptly. This study presents a bio-restoration method to improve the self-healing effectiveness of the cement-based materials cracks rapidly. Ceramsite carrier was used to immobilize bacteria, while substrate and nutrients mixed evenly were immobilized into other original carrier. The section surface of paste specimens before and after curing was investigated by staining. Water permeation coefficient and flexural strength test were applied to characterize the repairing effectiveness of specimens. Experimental results show that plenty of white precipitation generated on the section surface after curing 21 days and the apparent water permeation coefficient of specimens changed slightly after restoring 28 days. The area repair rate of section surface of the samples with bacteria and nutrients immobilized into ceramsite was run up to 87.5%. The flexural strength of specimens repaired could increase from 56% to 72% than other microbiological methods. SEM/EDS and XRD analysis results show that the precipitation formed in cracks is calcite.