Use of bacteria to repair cracks in concrete
ABSTRACT As synthetic polymers, currently used for concrete repair, may be harmful to the environment, the use of a biological repair technique is investigated in this study. Ureolytic bacteria such as Bacillus sphaericus are able to precipitate CaCO3 in their micro-environment by conversion of urea into ammonium and carbonate. The bacterial degradation of urea locally increases the pH and promotes the microbial deposition of carbonate as calcium carbonate in a calcium rich environment. These precipitated crystals can thus fill the cracks. The crack healing potential of bacteria and traditional repair techniques are compared in this research by means of water permeability tests, ultrasound transmission measurements and visual examination. Thermogravimetric analysis showed that bacteria were able to precipitate CaCO3 crystals inside the cracks. It was seen that pure bacteria cultures were not able to bridge the cracks. However, when bacteria were protected in silica gel, cracks were filled completely.
- SourceAvailable from: Huisu Chen
Dataset: C&C2013-11 3
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ABSTRACT: AIMS: Bacterially induced calcium carbonate precipitation from various isolates was investigated aiming at developing an environmentally friendly technique for ornamental stone protection and restoration. METHODS AND RESULTS: Microorganisms isolated from stone samples and identified using 16S rDNA and biochemical tests promoted calcium carbonate precipitation in solid and novel liquid growth media. Biomineral morphology was studied on marble samples with scanning electron microscopy. Most isolates demonstrated specimen weight increase, covering partially or even completely the marble surfaces mainly with vaterite. The conditions under which vaterite precipitated and its stability throughout the experimental runs are presented. CONCLUSIONS: A growth medium that facilitated bacterial growth of different species and promoted biomineralization was formulated. Most isolates induced biomineralization of CaCO3 . Microorganisms may actually be a milestone in the investigation of vaterite formation facilitating our understanding of geomicrobiological interactions. Pseudomonas, Pantoea and Cupriavidus strains could be candidates for bio-consolidation of ornamental stone protection. SIGNIFICANCE AND IMPACT OF THE STUDY: Characterization of biomineralization capacity of different bacterial species improves understanding of the bacterially induced mineralization processes and enriches the list of candidates for bio-restoration applications. Knowledge of biomineral morphology assists in differentiating mineral from biologically induced precipitates. This article is protected by copyright. All rights reserved.Journal of Applied Microbiology 04/2013; · 2.20 Impact Factor
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ABSTRACT: Crack is commonly observed failure in the case of concrete. Crack may develop due to addition of excess of water to during mixing of concrete, or may be due to shrinkage and creep. In the present study, crack healing and improvement of physical properties of cement paste, mortar and concrete are studied. It is done by the addition of bacterial strains namely Bacillus Sphaericus and Sporosarcina Pastuerii. It is found that these bacteria when added at 10 6 concentration of cells/ml of water to cement composites increased by about 39.8% and 33.07% in paste. There is an increment of 50% and 28.2% in mortar for two bacterial strains. The strength increment is found to be 18.3% and 12.2% for Bacillus Sphaericus and Sporosarcina Pastuerii respectively for concrete. Ultrasonic pulse velocity of the bacterial concrete was in line with conventional concrete. SEM and XRD images revealed presence of CaCO 3 produced microbially. There is overall improvement in the bacterial composites compared to conventional composites.