Investigating the effectiveness of a bacterial self-healing mechanism for repairing cracks in sustainable cement mortar at low temperatures

Abstract

Mortar forms a fundamental constituent of concrete, resulting in similar behavior and drawbacks between them. In this study, we investigate one of these drawbacks (cracks). This study investigates bacterial self-healing efficiency at different temperatures RT (24 °C), Zero, and Sub-Zero (-16 ± 2 °C, and – RT, (- 24 °C)), bacteria type, concentration, and percent on self-healing of cracks in cement mortar. The two distinct strains of bacteria were Bacillus Megaterium (BM) and Bacillus Sphaericus (BS), with varying concentrations of 0 %, 1 %, and 2.5 %. The efficiency of the bacterial strains was evaluated using a variety of techniques, such as compressive and flexural strength tests, energy-dispersive spectroscopy (EDS), scanning electron microscopy (SEM), and X-ray diffraction (XRD). It was observed that RT and Zero temperature at 2.5 % of BS or BM had the same behavior for crack-healing efficiency by 100 % with an improvement in the mechanical strength of the mortar. However, BM survived and kept healing the cracks in Sub-Zero temperatures, with a healing efficiency of 38.37 % after 56 days at the temperature of -16 ± 2 °C. Calcium carbonate was also detected by the SEM and EDS tests, indicating that the bacteria were actively taking part in the healing process for themselves.

Keywords

• Bacterial self-healing
• Bacillus megaterium
• Sustainability
• Calcium carbonate
• Mortar
• Sub-zero temperatures