Article

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

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.

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Available from: Willem De Muynck, Oct 01, 2015
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    • "Calcification potential of a bacterium emanates from its ability to breakdown urea enzymatically (DeMuynck et al., 2010;Tittelboom et al., 2010). E. coli DH5a is known to have no urease activity; therefore, it was used as a control strain for exclusive assessment of the influence of experimental.2016.01.016parameters on the activity of S. pasteurii strain harboring active urease gene (Kim and Spizizen, 1985;Stocks-Fischer et al., 1999;Tiwari et al., 2014). "
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    ABSTRACT: Sporosarcina pasteurii, a common soil bacterium has been tested for microbial treatment of cement mortar. The present study also seeks to investigate the effects of growth medium, bacterial concentration and different buffers concerning the preparation of bacterial suspensions on the compressive strength of cement mortar. Two growth media, six different suspensions and two bacterial concentrations were used in the study. The influence of growth medium on calcification efficiency of S. pasteurii was insignificant. Significant improvement in the compressive as well as the tensile strength of cement mortar was observed. Microbial mineral precipitation visualized by Scanning Electron Microscopy (SEM) shows fibrous material that increased the strength of cement mortar. Formation of thin strands of fillers observed through SEM micrographs improves the pore structure, impermeability and thus the compressive as well as the tensile strengths of the cement mortar. The type of substrate and its molarity have a significant influence on the strength of cement mortar.
    Full-text · Article · Jan 2016 · Saudi Journal of Biological Sciences
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    • "significant impact on the morphology of CaCO 3 ( De Muynck et al . , 2008a , b ; Van Tittelboom et al . , 2010 ; Achal et al . , 2011 ; Xu et al . , 2014 ) . In recent years , bacterial induced deposition in using a non - ureolytic pathway has also been found ( Jonkers et al . , 2010 ) . By mixing spores of these types of bacteria with fresh state concrete , self - healing of concrete cracks is expected since spores will germinate once cracking "
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    ABSTRACT: The biochemical properties of CaCO3 precipitation induced by Sporosarcina pasteurii, an ureolytic type microorganism, were investigated. Effects of calcium source on the precipitation process were examined, since calcium source plays a key role in microbiologically induced mineralization. Regardless of the calcium source type, three distinct stages in the precipitation process were identified by Ca2+, NH4+, pH and cell density monitoring. Compared with stage 1 and 3, stage 2 was considered as the most critical part since biotic CaCO3 precipitation occurs during this stage. Kinetics studies showed that the microbial CaCO3 precipitation rate for calcium lactate was over twice of that for calcium nitrate, indicating that calcium lactate is more beneficial for the cell activity, which in turn determines urease production and CaCO3 precipitation. X-ray diffraction analysis confirmed the CaCO3 crystal as calcite, although scanning electron microscopy revealed a difference in crystal size and morphology if calcium source was different. The findings of this paper further suggest a promising application of microbiologically induced CaCO3 precipitation in remediation of surface and cracks of porous media, e.g., cement-based composites, particularly by using organic source of calcium lactate.
    Full-text · Article · Dec 2015 · Frontiers in Microbiology
    • "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.
    No preview · Article · Sep 2015 · International Biodeterioration & Biodegradation
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