Crack Healing Performance of Microbial Self-Healing Concrete Using Different Carriers

Concrete structures are commonly associated with crack formation. Microcrack formation when left unattended may cause deterioration of concrete structures due to ingress of moisture and therefore needs to be repaired. Self-healing of concrete cracks through bacterial-induced calcium carbonate precipitation presents an effective way of healing the cracks without manual intervention. In this study, lightweight expanded clay aggregate (LECA), air-entraining admixture (AEA), and polyvinyl alcohol (PVA) fibers were used as bacterial carriers. Bacillus subtilis with a McFarland standard of 109 cells/ml was used in different dosages such as 0.01%, 0.1%, and 1% by cement weight. A total of nine mixes were developed and were differentiated based on bacterial carriers and encapsulation techniques. Seventy-five concrete prisms (1.5 × 1.5 × 6.3 in.3) were made and pre-cracked after 7 days and the healing performance was monitored using ultrasonic pulse velocity (UPV) testing and surface crack analysis. In addition, scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis were carried out to characterize the healing product. The results of the UPV and surface crack analysis indicated that the 1% dosage group showed superior healing performance as compared to the other two dosage groups. Similarly, SEM and XRD analysis confirmed calcite formation in the cracks of concrete prisms. This innovative approach aligns with the pressing need for preventive maintenance strategies to address the challenges posed by deteriorating infrastructure and contribute to a more sustainable future.