Kimyasal katkı malzemelerinin biyomineralizasyon ile kendiliğinden iyileşen çimento-esaslı malzemelerin performansına olan etkisi

Yıl 2019, Cilt: 2 Sayı: 1, 38 - 49, 15.06.2019

Zeynep Başaran Bundur , Ali Amiri

Öz

Beton yapıların servis ömrünü etkileyen faktörler birbirleriyle genellikle bağlantılıdır. Beton gevrek ve kırılgan doğası yüzünden, gerilmeler altında çatlayabilir. Son yıllarda yapılan araştırmalar kendiliğinden iyileşen çimento esaslı malzemelerin üretiminin mümkün olduğunu göstermiştir. Kendiliğinden iyileşme özelliği, betonun oluşan çatlakları kendiliğinden kapatabilmesidir ve bu amaçla kullanılabilecek yenilikçi yöntemlerden biri biyomineralizasyondur. Biyomineralizasyon mikroorganizmaların metabolik aktiviteleri sonucu ürün olarak kalsiyum karbonat (CaCO₃) oluşmasıdır. Bu oluşan ürün/CaCO₃çökeltisinin çatlakları doldurması ile kendiliğinden iyileşme elde edilir.Bu çalışmanın amacı, çimento-esaslı malzemelerde kendiliğinden iyileşmenin sağlanabilmesi için çimento hamuru içine katılan bakterilerin malzemenin performansına olan etkisinin incelenmesidir. Bu amaç doğrultusunda bakteriler sulu besi yerinde büyütüldükten sonra hiçbir işlem uygulanmadan çimento harcı içine katılmış ve performans değerlendirmesi priz süresi, basınç dayanımı, karbonizasyon ve kendiliğinden iyileşme kabiliyeti incelenerek belirlenmiştir. Bakterilerin harç içine eklenmesi kimyasal yapıyı ve basınç dayanımını olumsuz yönde etkilemez iken, priz süresinde belirgin bir artış olmuştur. Bu artış, bakteri ile beraber çimento içine katılan besi yeri ile ilişkilendirilmiştir. Çimento harcı içine karıştırılan bakteriler eğilme altında oluşturulan çatlakları kapatabilmiş, ürün/CaCO₃çatlakları doldurmuştur. Son olarak, süperakışkanlaştırıcı ve hava sürükleyici katkı (HSK) gibi sıkça kullanılan katkı malzemelerinin biyomineralizasyona olan etkileri incelenmiştir. Süperakışkanlaştırıcı kullanımı bakterilerin kendiliğinden iyileşmeyi sağlamasında olumlu  bir etki sağlarken, HSK’nın çatlak içinde CaCO3 çökelmesini kısmen azalttığı gözlemlenmiştir.

Anahtar Kelimeler

Kendliğinden iyileşme, priz süresi, biyomineralizasyon, basınç dayanımı, çimento harcı

Influence of chemical admixtures on performance of biomineralized self-healing cement-based materials

Öz

Factors affecting the durability of concrete structures are generally associated with each other. Due to its brittle nature, concrete can crack when stress is applied.  Recent research in the field proposes that it might be possible to develop a smart, cement-based material that can self-heal itself. Self-healing is the ability of concrete to heal the cracks without any external application. Self-healing property of concrete can be obtained via different approaches. Use of biomineralization is a novel technique to provide self-healing in cement-based materials. Biomineralization is a biochemical process in which microorganisms stimulate the formation of minerals. In this system, calcium carbonate (CaCO₃) is induced by leveraging the metabolic activity of microorganism and self-healing is obtained by sealing of the cracks with CaCO₃.The goal of this study to investigate the influence of bacterial self-healing agent on performance of cement-based materials. In this study, the bacteria will be introduced to cement paste with its growth media without any additional manipulation such as encapsulation. Performance of cement-based mortar was evaluated by Vicat needle test, compressive strength test, thermogravimetric analysis and crack healing ability. While incorporation of bacterial cells did not affect the compressive strength and chemical composition, there was a significant delay in initial setting time. This was attributed to the nutrient medium added along with bacterial cells. With this approach, the flexural cracks on the mortar surface were sealed with the CaCO₃. At last but not the least the influence of superplasticizers and air entraining agents (AEA) on self-healing was investigated. While the superplasticizers improved the self-healing efficiency of the bacterial cells, AEA relatively educed the amount of CaCO₃precipitation within the cracks.

Anahtar Kelimeler

Self-healing, cement-based mortar, biomineralization, compressive strength, initial settin time

Kaynakça

• Achal, Varenyam, Xiangliang Pan, and Nilüfer Özyurt. 2011. “Improved strength and durability of fly ash-amended concrete by microbial calcite precipitation.” Ecological Engineering 37 (4). Elsevier B.V.: 554–59. doi:10.1016/j.ecoleng.2010.11.009.
• Amiri, Ali, and Zeynep Başaran Bundur. 2018. “Use of corn-steep liquor as an alternative carbon source for biomineralization in cement-based materials and its impact on performance.” Construction and Building Materials 165: 655–62. doi:10.1016/j.conbuildmat.2018.01.070.
• Basaran, Zeynep. 2013. “Biomineralization in Cement Based Materials: Inoculation of Vegetative Cells.”Ph.D. Dissertation. Faculty of Civil, Architecture and Environmental engineering, University of Texas at Austin, Austin, TX, U.S.A.
• Bolobova, A V, and V I Kondrashchenko. 2000. “Use of Yeast Fermentation Waste as a Biomodifier of Concrete ( Review ).” Applied Biochemistry and Microbiology 36 (3): 205–14.
• Bundur, Z.B., S. Bae, M.J. Kirisits, and R.D. Ferron. 2017. “Biomineralization in Self-Healing Cement-Based Materials: Investigating the Temporal Evolution of Microbial Metabolic State and Material Porosity.” Journal of Materials in Civil Engineering 29 (8). doi:10.1061/(ASCE)MT.1943-5533.0001838.
• Bundur, Z.B., M.J. Kirisits, and R.D. Ferron. 2015. “Biomineralized Cement-Based Materials: Impact of Inoculating Vegetative Bacterial Cells on Hydration and Strength.” Cement and Concrete Research 67: 237–45. doi:10.1016/j.cemconres.2014.10.002.
• Bundur, Zeynep Başaran, Ali Amiri, Yusuf Cagatay Ersan, Nico Boon, and Nele De Belie. 2017. “Impact of air entraining admixtures on biogenic calcium carbonate precipitation and bacterial viability.” Cement and Concrete Research 98 (January): 44–49. doi:10.1016/j.cemconres.2017.04.005.
• Erşan, Yusuf Çağatay, Nele de Belie, and Nico Boon. 2015. “Microbially induced CaCO3 precipitation through denitrification: An optimization study in minimal nutrient environment.” Biochemical Engineering Journal 101. Elsevier B.V.: 108–18. doi:10.1016/j.bej.2015.05.006.
• Mann, Stephan. 2001. Biomineralization: Principles and Concepts in Bioinorganic Materials Chemistry. New York: Oxford.
• Muynck, Willem De, Nele De Belie, and W Verstraete. 2010. “Microbial carbonate precipitation in construction materials : A review.” Ecological Engineering 36: 118–36. doi:10.1016/j.ecoleng.2009.02.006.
• Rodriguez-Navarro, Carlos, Fadwa Jroundi, Mara Schiro, Encarnación Ruiz-Agudo, and María Teresa González-Muñoz. 2012. “Influence of substrate mineralogy on bacterial mineralization of calcium carbonate: Implications for Stone Conservation.” Applied and Environmental Microbiology 78 (11): 4017–29. doi:10.1128/AEM.07044-11.
• Sahmaran, Mustafa, Gurkan Yildirim, and Tahir K. Erdem. 2013. “Self-healing capability of cementitious composites incorporating different supplementary cementitious materials.” Cement and Concrete Composites 35 (1). Elsevier Ltd: 89–101. doi:10.1016/j.cemconcomp.2012.08.013.
• Stocks-Fischer, Shannon, Johnna K Galinat, and Sookie S Bang. 1999. “Microbiological precipitation of CaCO3.” Soil Biology and Biochemistry 31: 1563–71.Tittelboom, Kim Van, and Nele De Belie. 2013. “Self-healing in cementitious materials—A Review.” Materials 6 (May): 2182–2217. doi:10.3390/ma6062182.
• Wang, J.Y., D. Snoeck, S. Van Vlierberghe, W. Verstraete, and N. De Belie. 2014. “Application of hydrogel encapsulated carbonate precipitating bacteria for approaching a realistic self-healing in concrete.” Construction and Building Materials 68 (October). Elsevier Ltd: 110–19. doi:10.1016/j.conbuildmat.2014.06.018.
• Wang, J.Y., H. Soens, W. Verstraete, and N. De Belie. 2014. “Self-healing concrete by use of microencapsulated bacterial spores.” Cement and Concrete Research 56 (February). Elsevier Ltd: 139–52. doi:10.1016/j.cemconres.2013.11.009.
• Wang, Jianyun. 2013. “Self-healing concrete by means of immobilized carbonate precipitating bacteria.” Ghent University, Belgium.
• Wang, Jianyun, Kim Van Tittelboom, Nele De Belie, and Willy Verstraete. 2012. “Use of silica gel or polyurethane immobilized bacteria for self-healing concrete.” Construction and Building Materials 26 (1). Elsevier Ltd: 532–40. doi:10.1016/j.conbuildmat.2011.06.054.
• Wiktor, Virginie, and Henk M. Jonkers. 2011. “Quantification of crack-healing in novel bacteria-based self-healing concrete.” Cement and Concrete Composites 33: 763–70. doi:10.1016/j.cemconcomp.2011.03.012.