This research aims to study the bacterial healing process of cement mortar samples exposed to durability effects using bacteria characterized by their ability to precipitate calcium carbonate. Sporosarcina pasteurii is widely used for bacterial healing. This research investigates the performance of S. pasteurii with five types of bacteria isolated from caves (Viridibacillus arenosi, Streptomyces spororaveus, Bacillus zhangzhouensis, Stenotrophomonas rhizophila, and Serratia quinivorans). Cement mortar samples were exposed to high temperatures and freeze–thaw effects to create microcracks. Microcracks were also induced by applying flexural strength loads. Then, the formed microcracks were healed using spraying and injection of the bacterial solution for the first group for 90 days. The control and healed samples were assessed using flexural and compressive strength, water absorption, capillary water absorption, and ultrasonic pulse velocity (UPV) tests. Microstructural analysis was also conducted to evaluate the bacterial healing products. Subsequently, statistical analysis was performed using the results of these tests to compare the various bacterial efficiencies. As a result of the statistical analysis, the total efficiency scores obtained in the statistical analysis were 119 for Stenotrophomonas rhizophila, 112 for Viridibacillus arenosi, and 105 for S. pasteurii. Thus, Stenotrophomonas rhizophila and Viridibacillus arenosi showed the best healing performance compared to the other types of bacteria.

This study aimed to examine the calcite precipitation potential of non-ureolytic bacterial strains of two species, Viridibacillus arenosi (A₆) and Bacillus zhangzhouensis (D₂₅), as compared to the known ureolytic bacterial strain, Sporosarcina pasteurii (SP), within geopolymer mortar. Tests were carried out after 56 days of injection treatment to confirm the precipitation process, incorporating healing efficiency measured by ImageJ software, recovery of UPV, water permeability, capillary water absorption, and microstructural and mineralogical analysis SEM/EDS and XRD. The non-ureolytic isolates D₂₅ and A₆ showed the highest healing efficiencies, at 96.9% and 91.9%, respectively, followed by the ureolytic bacteria SP at 77.8%. A₆ exhibited the most substantial reduction in permeability at 97.3%, indicating extensive crack healing, followed by D₂₅ at 92.9% and SP at 82.1%. Furthermore, SEM and EDS analyses confirmed the formation of calcite crystals and calcium depositions in the bacteria-treated samples. Complementary evidence was provided by XRD, which revealed distinct calcium carbonate peaks in the treated specimens, peaks that were entirely absent in the control samples, thus strongly confirming the role of bacterial activity in the precipitation process. The results confirm that non-ureolytic bacteria can efficiently boost calcite precipitation in geopolymer mortars, offering superior healing performance and a more sustainable alternative to ureolytic strains.