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Biotratamento e bioformulação ecoeficientes de tijolo cerâmico e argamassa de cal aérea
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Os materiais de construção estão propensos a processos de degradação que, sob certas condições ou após algum tempo, causam danos. Bioformulação e biotratamento com produtos ecoeficientes são técnicas inovadoras que despertaram o interesse para otimização e proteção dos materiais de construção. Neste estudo atribui-se o termo bioformulação quando um bioproduto é utilizado na formulação e produção de novos ma-teriais de construção, por exemplo argamassas. Já o biotratamento é uma técnica em que um bioproduto é aplicado na superfície de materiais porosos ou em áreas localizadas, tais como fissuras. Estes efeitos refle-tem-se na proteção do material, atuando como um revestimento que reduz a absorção de água da chuva, e que, desde que não interfiram significativamente na secagem, aumentam a durabilidade. Essas biotecnologias baseiam-se nas atividades biológicas de enzimas ou células e frequentemente envolvem a precipitação de compostos químicos derivados do metabolismo bacteriano.
Estas técnicas têm sido aplicadas recentemente em diferentes materiais, desde solos a materiais cimen-tícios. Os biotratamentos podem ser mais ecológicos e compatíveis com materiais de construção antigos em comparação com outros tratamentos de superfície sintéticos disponíveis no mercado.
Neste trabalho, utilizaram-se bioprodutos inovadores de dois grupos: um com base em culturas de Es-cherichia coli suplementadas com ferro e outro com base em culturas microbianas mistas, cultivadas com produtos secundários industriais ou resíduos florestais. Estes bioprodutos foram utilizados em bioformula-ções de argamassas de cal aérea, para a otimização de algumas das suas características, e em biotratamentos realizados in situ, em tijolos expostos em parede, e em laboratório em provetes de tijolo cerâmico maciço e de argamassa de cal, para simular uma alvenaria de tijolo à vista e melhorar suas propriedades superficiais. Para além da aplicação dos bioprodutos diretamente após produção e após período de congelação, estes tam-bém foram utilizados liofilizados (em pó), tendo em vista a facilidade de transporte, armazenamento e prepa-ro em obra (bastando resuspender em água da torneira). Foram estudadas sete técnicas de aplicação: por go-tejamento com e sem alimentação, por pulverização, por contato com gaze umedecida, por pincelagem, por capilaridade e por imersão.
Os resultados obtidos com os biotratamentos indicam que os bioprodutos utilizados foram eficientes, tendo reduzido substancialmente a capacidade de absorção de água, quando comparado com os controles (provetes não tratados), e que melhores resultados desta redução foram obtidos quando o bioproduto foi apli-cado por meio de gotejamento e por imersão, este último até ao primeiro mês após aplicação. Observou-se também que visualmente não foram detectadas alterações cromáticas. Por fim, os resultados mostraram ainda que as argamassas bioformuladas apresentam melhores características de redução de absorção de água.
Building materials are prone to degradation processes which, under certain conditions or with time, cause damage. Bioformulation and biotreatment with eco-efficient products are innovative techniques that have awakened interest for optimization and protection of building materials. In this study, the term biofor-mulation is assigned when a bioproduct is used in the formulation and production of new building materials, such as mortars. Biotreatment is a technique where a bioproduct is applied at the surface of a porous materi-als or cracked areas. These effects are reflected in the material's protection, acting as a coating that reduces rainwater absorption and, if without significantly interfering with drying, increases durability. These bio-technologies are based on the biological activities of enzymes or bacterial cells, and frequently involve pre-cipitation of chemical compounds derived from bacterial metabolism. These techniques have been recently applied to different materials, from soils to cementitious materi-als. Biotreatments can be more ecological and compatible with old construction materials in comparison with other synthetic available surface treatments on the market. In this work, the bioproducts used are divided into two groups: one based on cultures of Escherichia coli supplemented with iron and another based on mixed microbial cultures, grown with industrial by-products or forest residues. These bioproducts were used in air lime mortar bioformulations, to optimize some of their characteristics, and, as biotreatments, in situ on exposed bricks and in laboratory samples of solid ceramic bricks and lime mortars, to simulate unrendered brick masonry with exposed joints, and to im-prove their surface properties. Bioproducts were used after being produced but also after being freezed. Ly-ophilized bioproducts (powder) were also used, in view of the ease of transport, storage and preparation on site (just resuspending in tap water). Seven application techniques were studied: dropping without and with feeding, spraying, poultice by impregnated gauze, brushing, capillarity and immersion. The results obtained with the biotreatments indicate that the bioproducts used were efficient, having substantially reduced water absorption capacity when compared to controls (untreated samples), and that bet-ter results of this reduction were obtained when the bioproduct was applied by dropping and by immersion, the latter until the first month after application. It was also observed that visually no chromatic alterations were detected. Finally, the results also showed that the bioformulated mortars reduce the water absorption.
Building materials are prone to degradation processes which, under certain conditions or with time, cause damage. Bioformulation and biotreatment with eco-efficient products are innovative techniques that have awakened interest for optimization and protection of building materials. In this study, the term biofor-mulation is assigned when a bioproduct is used in the formulation and production of new building materials, such as mortars. Biotreatment is a technique where a bioproduct is applied at the surface of a porous materi-als or cracked areas. These effects are reflected in the material's protection, acting as a coating that reduces rainwater absorption and, if without significantly interfering with drying, increases durability. These bio-technologies are based on the biological activities of enzymes or bacterial cells, and frequently involve pre-cipitation of chemical compounds derived from bacterial metabolism. These techniques have been recently applied to different materials, from soils to cementitious materi-als. Biotreatments can be more ecological and compatible with old construction materials in comparison with other synthetic available surface treatments on the market. In this work, the bioproducts used are divided into two groups: one based on cultures of Escherichia coli supplemented with iron and another based on mixed microbial cultures, grown with industrial by-products or forest residues. These bioproducts were used in air lime mortar bioformulations, to optimize some of their characteristics, and, as biotreatments, in situ on exposed bricks and in laboratory samples of solid ceramic bricks and lime mortars, to simulate unrendered brick masonry with exposed joints, and to im-prove their surface properties. Bioproducts were used after being produced but also after being freezed. Ly-ophilized bioproducts (powder) were also used, in view of the ease of transport, storage and preparation on site (just resuspending in tap water). Seven application techniques were studied: dropping without and with feeding, spraying, poultice by impregnated gauze, brushing, capillarity and immersion. The results obtained with the biotreatments indicate that the bioproducts used were efficient, having substantially reduced water absorption capacity when compared to controls (untreated samples), and that bet-ter results of this reduction were obtained when the bioproduct was applied by dropping and by immersion, the latter until the first month after application. It was also observed that visually no chromatic alterations were detected. Finally, the results also showed that the bioformulated mortars reduce the water absorption.
Descrição
Palavras-chave
Tratamento superficial argamassa de cal aérea Escherichia coli com ferro resíduos de glicerol e de pinheiro alvenarias de tijolo cerâmico juntas de argamassa