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Diatomaceous earth as a protective vehicle for bacteria applied for self-healing concrete.
MedLine Citation:
PMID:  21927907     Owner:  NLM     Status:  Publisher    
Abstract/OtherAbstract:
Crack repair is crucial since cracks are the main cause for the decreased service life of concrete structures. An original and promising way to repair cracks is to pre-incorporate healing agents inside the concrete matrix to heal cracks the moment they appear. Thus, the concrete obtains self-healing properties. The goal of our research is to apply bacterially precipitated CaCO(3) to heal cracks in concrete since the microbial calcium carbonate is more compatible with the concrete matrix and more environmentally friendly relative to the normally used polymeric materials. Diatomaceous earth (DE) was used in this study to protect bacteria from the high-pH environment of concrete. The experimental results showed that DE had a very good protective effect for bacteria. DE immobilized bacteria had much higher ureolytic activity (12-17 g/l urea was decomposed within 3 days) than that of un-immobilized bacteria (less than 1 g/l urea was decomposed within the same time span) in cement slurry. The optimal concentration of DE for immobilization was 60% (w/v, weight of DE/volume of bacterial suspension). Self-healing in cracked specimens was visualized under light microscopy. The images showed that cracks with a width ranging from 0.15 to 0.17 mm in the specimens containing DE immobilized bacteria were completely filled by the precipitation. Scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS) were used to characterize the precipitation around the crack wall, which was confirmed to be calcium carbonate. The result from a capillary water absorption test showed that the specimens with DE immobilized bacteria had the lowest water absorption (30% of the reference ones), which indicated that the precipitation inside the cracks increased the water penetration resistance of the cracked specimens.
Authors:
J Y Wang; N De Belie; W Verstraete
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2011-9-17
Journal Detail:
Title:  Journal of industrial microbiology & biotechnology     Volume:  -     ISSN:  1476-5535     ISO Abbreviation:  -     Publication Date:  2011 Sep 
Date Detail:
Created Date:  2011-9-19     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  9705544     Medline TA:  J Ind Microbiol Biotechnol     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
Affiliation:
Magnel Laboratory for Concrete Research, Faculty of Engineering and Architecture, Ghent University, Technologiepark Zwijnaarde 904, 9052, Ghent, Belgium, jianyun.wang@ugent.be.
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