The effect of isolated Bacillus ureolytic bacteria in improving the bio-healing of concrete cracks

Abstract

Background Reinforcement corrosion and the concrete strength reduction are critical problems that resulted from crack creation in concrete. Very expensive and hazardous technologies based on chemical materials have been provided for repairing the cracks. Recently, crack repair using bio-catalysis precipitating bacteria has been developed as a viable and ecofriendly alternative technique. The main target of this study was to select and identify bacterial isolates with high urease activity to use in filling the cracks by the precipitation of CaCO3. Results Two endospore-forming and alkali-resistant ureolytic bacteria were combined with concrete to tolerate the mechanical stresses generated by mixing. The two isolates designated as (B1 and B2) were selected and identified as Bacillus wiedmannii strain FSL W8-0169 and Bacillus paramycoides strain MCCC 1A04098, respectively, using 16SrDNA gene sequencing. Both bacterial species completely heal cracks in fully destructed concrete and significant enhancement in compressive strength was illustrated. The calcite filling of cracks and CaCO3 crystals that were screened using a scanning electron microscope may explain the crack healing and the enhancement in concrete strength. Conclusions Bacillus wiedmannii strain FSL W8-0169 and Bacillus paramycoides strain MCCC 1A04098 can be inserted with the concrete to improve the compressive strength and the self-healing of cracks. The two ureolytic bacterial strains can be used to protect water buildings from exposure to frequent cracks.

Impact of the immobilized Bacillus cereus MG708176 on the characteristics of the bio-based self-healing concrete

“…For the bacterial spores harvesting, the bacterial isolate was cultured for 24 h in alkaline nutrient broth (D (+)-glucose, 1 g/L, peptone, 15 g/L, sodium chloride, 6 g/L, yeast extract, 3 g/L, and then adding NaOH solution droplets until pH 14). The amended spore concentration in samples was 1.3 × 10 7 spore/cm 3 of the entire concrete mixture 18 . The nutrients, including 40 g/L calcium chloride anhydrous, 65 g/L urea, and 2 g/L yeast extract were dissolved in sterilized tap water for preparing the bio-based concrete.…”

“…The procedure of the endospore staining was performed as shown by Mokhtar et al . 18 . Alkali solid medium was prepared by adding NaOH solution droplets until pH = 14 to nutrient agar (NA) (5 g peptone, 3 g beef extract, 8 g sodium chloride, and 15 g agar dissolved 1000 mL distilled water) and the bacterial isolate was cultivated on its surface 18 .…”

“… 18 . Alkali solid medium was prepared by adding NaOH solution droplets until pH = 14 to nutrient agar (NA) (5 g peptone, 3 g beef extract, 8 g sodium chloride, and 15 g agar dissolved 1000 mL distilled water) and the bacterial isolate was cultivated on its surface 18 . The urease test described by Christensen 19 was made.…”

Phylogenetic Analysis of UreABC Protein in Ureolytic Bacteria as Self-Healing Agent in Concrete

“…The increase in compressive strength caused by the entry of bacteria may occur due to calcite that precipitates on the surface of the microorganism cells and concrete pores. The insignificant increase in compressive strength of the media control specimens alone without spore inoculation indicated that media nutrition had no practical effect on increasing strength [23].…”

“…These external factors are keys of bacteria's metabolism to precipitate CaCO₃ (Figure 2) [36]. The precipitation of CaCO₃ is based on the enzymatic reaction by using urease [23]. According to the research [39], the self-healing ratio resulted 44,71% efficiency of incorporation Jsmartech.ub.ac.id of added bacteria in the concrete.…”