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Bioformulation and biotreatment of construction materials
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Resumo(s)
Bioconsolidation of construction materials is a consolidation technique that has recently gained relevance due to its eco-efficiency. This technique uses bioproducts that have been produced by biologic systems; they may contain as major component, microorganisms or biopolymers. This innovative technique has recently been studied and frequently applied in cementitious materials and in the stabilization of sands and soils. Studies of its application in lime and earth-based mortars are rare.
In the present study, developed within project DB – Heritage, different bioproducts were used. Two of them were obtained through waste biomass from a microbial mixed culture for polyhydroxyalkanoates production process, using glycerol, a by-product form biodiesel production (BF - biofuel), and the second using pine biomass (BM - biomass) as substrates for bacterial growth. A third bioproduct was assessed consisting in Escherichia (E.) coli cultures supplemented grown in the presence of iron (E. coli+Fe). Two application techniques were studied: bioformulation, which consists on using bioproducts as a kneading liquid to produce mortars, and biotreatment, which consists on applying the bioproducts by deposition on the surface of the specimen. The bioproduct BF was used to bioformulate cement mortars, natural hydraulic lime mortars and air lime mortars. The same BF bioproduct and the bioproduct with E. coli bacterium supplemented with iron were used to biotreat specimens of cement and an air lime mortar, limestone, fired brick, compressed earth block (CEB) and extruded earth blocks. Finally, the bioproduct BM was used to biotreat specimens of earth plastering mortars, conventional concrete and an identical concrete but with aggregates from construction and demolition wastes (CDW).
The results obtained with the bioformulated mortars were promising, since they show a significant reduction in water absorption and a slight improvement of their mechanical properties. Regarding the biotreatments, it is concluded that, despite some loss of resistance to water absorption in the long term, all the tested materials remain considerably more resistant to water absorption when compared with the control specimens.
Based on the obtained results it can be stated that the bioconsolidation of construction materials is a viable and interesting technique to deepen its study.
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Palavras-chave
Bioconsolidation Bioproduct from microbial mixed cultures E. coli and iron-based bioproduct Bioformulation Biotreatment Water absorption resistance