Influence of urea and calcium dosage on the effectiveness of bacterially induced carbonate precipitation on limestone |
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| Authors: | Willem De Muynck Kim Verbeken Nele De Belie Willy Verstraete |
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| Institution: | 1. Magnel Laboratory for Concrete Research, Department of Structural Engineering, Ghent University, Technologiepark Zwijnaarde 904, 9052 Gent, Belgium;2. Laboratory for Microbial Ecology and Technology (LabMET), Department of Biochemical and Microbial Technology, Ghent University, Coupure Links 653, 9000 Gent, Belgium;3. Department of Materials Science and Engineering, Technologiepark Zwijnaarde 903, 9052 Gent, Belgium;1. Laboratory of Microbial Ecology and Technology (LabMET), Ghent University, Coupure Links 653, B-9000 Ghent, Belgium;2. Avecom NV, Industrieweg 122 P, 9032 Wondelgem, Belgium;3. Magnel Laboratory for Concrete Research, Ghent University, Technologiepark – Zwijnaarde 904, B-9052 Ghent, Belgium;1. Innovative Construction Materials Research Unit, Department of Civil Engineering, Faculty of Engineering, Chulalongkorn University, Bangkok, Thailand;2. Department of Civil Engineering, Faculty of Engineering, Chulalongkorn University, Bangkok, Thailand;3. Department of Environmental Engineering, Faculty of Engineering, Chulalongkorn University, Bangkok, Thailand;4. Research Network of NANOTEC-CU on Environmental, Thailand;5. Centre of Excellence in Geotechnical and Geoenvironmental Engineering, Department of Civil Engineering, Faculty of Engineering, Chulalongkorn University, Bangkok, Thailand;1. Laboratory of Microbial Ecology and Technology (LabMET), Ghent University, Coupure Links 653, Ghent B-9000, Belgium;2. Magnel Laboratory for Concrete Research, Ghent University, Technologiepark – Zwijnaarde 904, Ghent B-9052, Belgium |
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| Abstract: | Bacterially induced carbonate precipitation has been explored for the protection and consolidation of ornamental stone. Attempts to improve the efficiency of this biodeposition process were primarily focused on the microbial aspects, i.e. type of microorganism and metabolic pathway. In this study, the influence of the chemical parameters, i.e. concentration of calcium salts and urea, on the effectiveness of the biodeposition treatment has been examined. The amount of calcium carbonate that can be precipitated in the stone is conditioned both by the amount of cells retained in the stone and the concentration of urea and calcium used. From sonication experiments, a good consolidation was observed for limestone prisms treated with a calcium dosage of 17 g Ca2+ m?2 with no improvement at higher concentrations. For limestone prisms of 4 cm × 2 cm × 1 cm, the biodeposition treatment resulted in a 63% lower weight loss upon sonication compared to untreated specimens. The waterproofing effect was observed to increase with increasing calcium dosages. While for a calcium dosage of 17 g Ca2+ m?2 the water absorption was similar to that of untreated specimens, concentrations of 67 g Ca2+ m?2 resulted in a 50% decrease of the rate of water absorption. For calcium dosages higher than 34 g Ca2+ m?2 a significant change in the visual aspect (ΔE > 6) of the treated stones could be observed. Overall, the urea/calcium chloride-based biodeposition treatment attained a protective performance comparable with that of the commonly used ethylsilicates. |
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