A selected bacterial strain for the self-healing process in cementitious specimens without cell immobilization steps.

The use of microorganisms capable of mediating the bioprecipitation process can be an important application in the self-healing processes of cement specimens. Thus, the present study identified and evaluated five Bacillus strains for potential application in the protocol of self-healing via bioprecipitation. Cell growth, enzyme production, and kinetic parameters conditions were evaluated during the fermentation process. Based on the analysis of 16S rDNA in conjunction with biochemical testing, results demonstrate that the strains are either Bacillus cereus or Bacillus thuringiensis. Strategically it was found that the addition of glycerol to fermentative medium was essential to increase the bacterial concentration (≈ 4.2 × 107 cells mL-1) and production of the enzyme urease (≈ 3.623,2 U.mL-1). The addition of this medium after 40 days of fermentation promoted the self-healing of cracks and increased compressive strength in ≈ 14.2% of the cementitious specimens; therefore, increasing the sustainability and engineering properties of cement-based materials.