Análise da viabilidade da reutilização das águas de lavagens dos caminhões betoneiras para produção de concreto
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Data
2018-06-28
Tipo de documento
Dissertação
Título da Revista
ISSN da Revista
Título de Volume
Área do conhecimento
Engenharias
Modalidade de acesso
Acesso aberto
Editora
Autores
Cardoso, Viviam Aparecida Vaz Pedrozo
Orientador
Rocha, Carlos Antônio
Coorientador
Resumo
Atualmente é notório o fato de que os custos ambientais associados à maioria das atividades econômicas representam uma fatia considerável do orçamento de um empreendimento, podendo chegar a 20% dos custos totais. No caso da Construção Civil, os resíduos gerados estão no intervalo de 0,40 a 0,50 ton/hab.ano, valores que estão acima da produção de lixo urbano por habitante. Existem estimativas de que o volume médio mensal de resíduos para descarte em uma usina de concreto está em torno de 2% de sua produção mensal. Entretanto, o reaproveitamento desses resíduos gerados encontra-se em estágio incipiente no Brasil. Os efluentes oriundos da lavagem dos caminhões betoneira são os que merecem maior atenção, devido ao grande volume de água destinado para essa lavagem. Nesse sentido, no presente trabalho estudou-se a reutilização dessas águas residuais para a produção de novos concretos, dispensando tratamentos prévios, através do uso de águas de lavagem (a) produzidas em laboratório, de diversas densidades e (b) colhidas na usina concreteira em seus diferentes níveis de decantação. A qualidade dessas águas residuais foi analisada quimicamente e os resultados mostraram que esta atende às normas técnicas para a produção de concretos e argamassas. De acordo com a metodologia adotada, a densidade e o pH das águas residuais foram utilizados como parâmetros de observação para a fabricação desses novos concretos, cujo desempenho foi avaliado através de quatro ensaios para sua fase fresca e seis ensaios para sua fase endurecida. O objetivo da realização desses ensaios foi verificar se ocorreram indícios de possíveis alterações das propriedades do concreto nos estados fresco e endurecido que viessem acarretar queda no desempenho. Foram realizados os ensaios de migração de cloretos, retenção de água, início e fim de pega, tração por flexão, resistência à compressão axial, módulo de elasticidade dinâmico, “flow table”, absorção de água por capilaridade, porosidade e calorimetria. O emprego de águas residuais não provocou alterações significativas na cinética de hidratação do cimento, conforme resultados do ensaio de calorimetria. Em particular, foram observadas uma redução da porosidade do novo concreto e um leve aumento da resistência à compressão axial. Esses resultados viabilizam a reutilização de águas residuais do processo de lavagem sem que sejam realizados quaisquer tipos de tratamentos ou separação dos sólidos incorporados.
Nowadays, it is well known that the environmental costs associated with most economic activities account for a considerable portion of a business's budget, bearing almost 20 percent of total costs. In the case of Civil Construction, the waste generated is in the range of 0.40 to 0.50 ton / inhab.years, values that are above the production of urban waste per inhabitant. There are estimates that the average monthly volume of waste for disposal at a concrete plant is around 2% of its monthly output. However, the reuse of these generated residues is in an early stage in Brazil. The effluents from the washing of concrete mixers are the ones that deserve greater attention, due to the large volume of water destined for this washing. In this sense, in the present work the reutilization of this wastewater for the production of new concretes was studied, dispensing with previous treatments, using washing waters (a) produced in the laboratory, of different densities and (b) collected at the concrete plant in its different levels of decantation. The quality of this wastewater was analyzed chemically and the results showed that it meets the technical standards for the production of concrete and mortars. According to the methodology adopted, the density and pH of the wastewater were used as observational parameters for the production of these new concretes, whose performance was evaluated through four tests for its fresh phase and six tests for its hardened phase. The objective of these tests was to verify if there were indications of possible alterations of the properties of the concrete in the fresh and hardened states that will lead to a decrease in its performance. Chloride migration, water retention, setting time, flexural tensile strength, axial compression strength, dynamic elastic modulus, flow table, water absorption by capillarity, porosity and calorimetry tests were performed. The use of wastewater did not cause any significant changes in the hydration kinetics of the cement, according to results of the calorimetry test. In particular, a reduction of the porosity of the new concrete and a slight increase in the resistance to axial compression were observed. These results allow the reuse of wastewater from the washing process without any type of treatment or separation of the incorporated solids.
Nowadays, it is well known that the environmental costs associated with most economic activities account for a considerable portion of a business's budget, bearing almost 20 percent of total costs. In the case of Civil Construction, the waste generated is in the range of 0.40 to 0.50 ton / inhab.years, values that are above the production of urban waste per inhabitant. There are estimates that the average monthly volume of waste for disposal at a concrete plant is around 2% of its monthly output. However, the reuse of these generated residues is in an early stage in Brazil. The effluents from the washing of concrete mixers are the ones that deserve greater attention, due to the large volume of water destined for this washing. In this sense, in the present work the reutilization of this wastewater for the production of new concretes was studied, dispensing with previous treatments, using washing waters (a) produced in the laboratory, of different densities and (b) collected at the concrete plant in its different levels of decantation. The quality of this wastewater was analyzed chemically and the results showed that it meets the technical standards for the production of concrete and mortars. According to the methodology adopted, the density and pH of the wastewater were used as observational parameters for the production of these new concretes, whose performance was evaluated through four tests for its fresh phase and six tests for its hardened phase. The objective of these tests was to verify if there were indications of possible alterations of the properties of the concrete in the fresh and hardened states that will lead to a decrease in its performance. Chloride migration, water retention, setting time, flexural tensile strength, axial compression strength, dynamic elastic modulus, flow table, water absorption by capillarity, porosity and calorimetry tests were performed. The use of wastewater did not cause any significant changes in the hydration kinetics of the cement, according to results of the calorimetry test. In particular, a reduction of the porosity of the new concrete and a slight increase in the resistance to axial compression were observed. These results allow the reuse of wastewater from the washing process without any type of treatment or separation of the incorporated solids.
Palavras-chave
Águas de lavagem de betoneira, Efluentes de usinas de concreto, Qualidade do concreto, Bate-lastro