CONICET | Buscador de Institutos y Recursos Humanos

Concrete is one of the most used building materials due to its inherent benefits of durability, strength, safety, and affordability to create flexible construction materials.However, one of the inevitable consequences of long-term usage of cement-based materials is the formation of microcracks within the structure. Traditional approaches which have been used to repair fissured materials are, for example, the use of epoxy resin or polyurethane to seal the cracks. Over recent years, an alternative repair technology to address many environmental and engineering issues was an application of biological substances to enhance the mechanical properties of cement, namely biologically controlled mineralization and biologically induced mineralization. The specific strength improvement via bacterial mineralization is called microbial-induced calcium carbonate precipitation (MICP) and is based on the introduction of calcite-forming bacteria to increase the self-healing ability and strength of building materials.The activity of microbial cementation on granular behavior is dependent on the ability of microbes to freely move either by injection throughout the pore space or by sufficient particle-particle contacts so that the cementation will be produced. These conditions require a balanced relationship between the microbe size and the pore between the sand particles. The scope of this work was to investigate the ability of Lysinibacillus sphaericus to precipitate CaCO3 using different mixed cement mortar.In this study, the feasibility of introducing calcite-forming L. sphaericus, into cement mortar to improve its mechanical performance was investigated. Biomortar was produced by microbial-induced calcite precipitation in the space between the particles of granular material by using as a mixing water a solution containing bacteria andurea as the substrate. The biomortar sample was subjected to physic-mechanical tests to evaluate the influence of calcite precipitation on cement mortar properties. The biomortar samples were cured for in an environmental chamber (23 ± 2°C - HR%≥ 95% ± 5%) and the compressive strengths were measured. L. sphaericus was grown and was mixed with aqueous urea solution. Biomortar samples were elaborated by mixing cement:sand: L. sphaericus aqueous urea solution (ratio of 1:3:0.5). Mortar samples without bacterial inoculation were set up as a control. Each set of mortar and biomortar was carried out in duplicate. We analyzed the presence/viability of this bacterium after these different conditions.The benefits of using MICP are that it can heal the cracks from the inside, resulting in the homogeneity of the repaired materials, and is often more environmentally friendly since no toxic chemicals or high consumption of energy.

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