Use of bacteria to repair cracks in concrete. Cem Concr Res

Magnel Laboratory for Concrete Research, Ghent University, Department of Structural Engineering, Technologiepark Zwijnaarde 904, B-9052 Ghent, Belgium
Cement and Concrete Research (Impact Factor: 2.86). 03/2013; DOI: 10.1016/j.cemconres.2009.08.025


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.

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Available from: Willem De Muynck, Oct 01, 2015
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    • "Biocalcification has been used in a wide range of applications (De Muynck et al., 2010a, and references therein). Various biocalcifying microorganisms have been used for protection of cementitious building materials (Chunxiang et al., 2009; Zamarre~ no et al., 2009) and for remediation of concrete cracks (Ramachandran et al., 2001; Van Tittelboom et al., 2010). Another use for biocalcite could be to lighten and hence improve the reflectivity of darker-coloured materials . "
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    ABSTRACT: Fiber cement panels were treated with urea and various calcium solutions with and without live or dead cells of Bacillus sphaericus LMG 222 57, to produce a surface layer of biocalcite; they were then exposed to the environment in São Paulo, Brazil, for 22 months. The calcifying treatment that produced the most colonisation-resistant surface was living bacteria + medium B4 + urea. The resistance of these biocalcified panels was related to their low water absorption, porosity and surface hydrophilicity, linked to the smaller size of the crystals compared to other treatments. Carbonation of the fiber cement before calcification visually increased biofilm formation, but the same calcifying treatment produced highest fouling resistance in this pre-carbonated group. Control samples, without calcification, allowed the development of considerable fouling, sometimes including the filamentous cyanobacterial genus, Scytonema, indicative of mature sub-aerial biofilms. There was no significant visual degradation of the calcite crystals associated with the colonising fungi and phototrophs after 22 months’ exposure. Biocalcification may safely be used to reduce the fouling-associated darkening of fiber cement and for protection and repair of cementitious building materials.
    International Biodeterioration & Biodegradation 09/2015; 103. DOI:10.1016/j.ibiod.2015.04.003 · 2.13 Impact Factor
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    • "The tomography analysis was performed at different ages (cracking day, 7, 14, 21 and 28 days). The second experimental approach consists in measuring air flow to assess selfhealing in mortars cracked at 7 days with a mechanical expansive core [3]. Only the mortars made with GU and GU+S were tested with this technique. "

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    • "It can also be used for enhanced oil recovery, prevention of acid mine drainage, for remediation of granite, mortar, limestone and concrete (Ramakrishnan et al. 2001; Zhong and Islam 1995). The calcite precipitation induced by Bacillus pasteruii and Bacillus sphaericus was found to be effective in remediating cracks of concrete and increased its compressive strength (Ramakrishnan et al. 2001; Van Tittelboom et al. 2010). The durability of concrete specimens treated with B. pasteruii exposed to alkaline, sulphate and freeze–thaw environments was also reported to increase (Ramakrishnan et al. 2005). "
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    ABSTRACT: The objective of this research work is to isolate and identify calcite precipitating bacteria and to check the suitability of these bacteria for use in concrete to improve its strength. Bacteria to be incorporated in concrete should be alkali resistant to endure the high pH of concrete and endospore forming to withstand the mechanical stresses induced in concrete during mixing. They must exhibit high urease activity to precipitate calcium carbonate in the form of calcite. Bacterial strains were isolated from alkaline soil samples of a cement factory and were tested for urease activity, potential to form endospores and precipitation of calcium carbonate. Based on these results, three isolates were selected and identified by 16S rRNA gene sequencing. They were identified as Bacillus megaterium BSKAU, Bacillus licheniformis BSKNAU and Bacillus flexus BSKNAU. The results were compared with B. megaterium MTCC 1684 obtained from Microbial Type Culture Collection and Gene Bank, Chandigarh, India. Experimental work was carried out to assess the influence of bacteria on the compressive strength and tests revealed that bacterial concrete specimens showed enhancement in compressive strength. The efficiency of bacteria toward crack healing was also tested. Substantial increase in strength and complete healing of cracks was observed in concrete specimens cast with B. megaterium BSKAU, B. licheniformis BSKNAU and B. megaterium MTCC 1684. This indicates the suitability of these bacterial strains for use in concrete. The enhancement of strength and healing of cracks can be attributed to the filling of cracks in concrete by calcite which was visualized by scanning electron microscope. Copyright © 2015 Elsevier GmbH. All rights reserved.
    Microbiological Research 05/2015; 174. DOI:10.1016/j.micres.2015.03.009 · 2.56 Impact Factor
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