Caracterização e reciclagem de resíduos cerâmicos de construção civil para aplicação como adição pozolânica e como componente de clínqueres visando novos cimentos
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Data
2020-12-14
Autores
Augusto Junior, José
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Universidade Estadual Paulista (Unesp)
Resumo
Diante das demandas ambientais ligadas ao setor da construção civil tanto no que diz respeito à geração e descarte incorreto de resíduos quanto no que tange o grande consumo de recursos naturais e emissão de poluentes ligados à produção do cimento, o presente trabalho consistiu no estudo do potencial incremento de Resíduos de Cerâmica Vermelha (RCV) provindos de blocos de alvenaria utilizados no setor da construção civil de maneira simultânea como adição pozolânica a cimento Portland e também como matéria prima a compor clínqueres em substituição total à argila natural, em virtude da similaridade das demandas químicas exigidas pelas duas aplicações. Os RCV foram coletados e beneficiados através de moinhos e foram submetidos a testes de Fluorescência de Raios X (FRX), Difratometria de Raios X (DRX) e Massa Específica de modo a caracterizá-los. Posteriormente foi definido o potencial pozolânico do material a partir do índice de desempenho com cimento Portland aos 28 dias, da atividade com cal aos 7 dias e verificação da composição química, sendo todos os resultados comparados aos requisitos determinados pelas normas NBR12653/2015 a ASTM C618/2019. Para a aplicação como componente de clínquer foi realizada a formulação da farinha a partir dos parâmetros químicos: Fator de Saturação de Cal (FSC), Módulo de Sílica (MS) e Módulo de Alumina (MA). A farinha foi submetida a tratamentos térmicos em três diferentes temperaturas, sendo essas 1300°C, 1380°C e 1420°C. Os produtos das sinterizações foram avaliados por meio de FRX e DRX, sendo também realizado o refinamento da estrutura cristalina através do método de Rietveld, de modo a acompanhar a influência das temperaturas na formação das fases. A composição química do RCV se mostrou rica em sílica, alumina e óxido de ferro, o que é vantajoso para adições minerais ativas em cimento e compatível com os ideais para argilas que compõem clínqueres. Com a análise de atividade pozolânica, concluiu-se, a partir de uma perspectiva panorâmica de suas características físicas e químicas, que o material apresenta reatividade na maneira como foi beneficiado, compreendendo, inclusive, em um acréscimo de 4% de resistência à compressão na argamassa em que foi incorporado. No que diz respeito aos produtos das sinterizações, constatou-se a obtenção de clínqueres belíticos a partir dos tratamentos térmicos feitos a 1300°C e 1380°C e clínquer Portland a 1420°C, sendo tais conclusões embasadas através da verificação de alterações proporcionais entre a formação de cristais de Alita e Belita nas amostras. Além disso, todos os clínqueres apresentaram desenvolvimento satisfatório das fases intersticiais e baixa detecção de cristais de Cal Livre, indicando a formulação adequada da farinha, condições de queima e resfriamento apropriadas e a dedução de que as proporções de Periclásio verificadas podem não serem prejudiciais aos cimentos compostos pelos clínqueres obtidos. Diante de tais verificações, estima-se que os clínqueres desenvolvidos nesta pesquisa, a partir de material amplamente descartado e disponível, podem compôr cimentos belíticos, possibilitando aplicação em obras de grande vulto que exijam baixo calor de hidratação e também cimentos Portland, cuja cura é mais rápida e o uso é amplamente difundido.
In reason of the environmental demands linked to the civil construction sector, both with regard to the generation and incorrect disposal of waste and with regard to the large consumption of natural resources and the emission of pollutants linked to the production of cement, the present work consisted of studying the potential increment of the Red Ceramic Waste (RCW) from masonry blocks used in the civil construction sector simultaneously as a pozzolanic addition to Portland cement and also as a raw material to compose clinkers in total substitution to natural clay, due to the similarity of demands chemicals required by the two applications. The RCWs were collected and processed through mills and underwent X-Ray Fluorescence (XRF), X-Ray Diffractometry (XRD) and Specific Mass tests in order to characterize them. Subsequently, the pozzolanic potential of the material was defined from the performance index with Portland cement at 28 days, from the activity with lime at 7 days and verification of the chemical composition, all the results being compared to the requirements determined by the standards NBR 12653/2015 to ASTM C618/2019. For application as a clinker component, the flour was formulated based on the chemical parameters: Lime Saturation Factor (LSF), Silica Ratio (SR) and Alumina Ratio (AR). The flour was subjected to heat treatment at three different temperatures, that went 1300°C, 1380°C and 1420°C. The sintering products were evaluated by means of fluorescence and X-ray diffraction, and the crystalline structure was refined using the Rietveld method, in order to monitor the influence of temperatures on the formation of the phases. The chemical composition of RCW proved to be rich in silica, alumina and iron oxide, which is advantageous for active mineral additions in cement and compatible with ideals for clays that compose clinkers. With the analysis of pozzolanic activity, it was concluded, from a panoramic perspective of its physical and chemical characteristics, that the material showed reactivity in the way it was benefited, and resulted, even, in an increase of 4% of compressive strength in the mortar in which it was incorporated. With regard to sintering products, it was found that belitic clinkers were obtained from heat treatments carried out at 1300°C and 1380°C and Portland clinker at 1420°C, with such conclusions based on the verification of proportional changes between the formation of Alita and Belita crystals in the samples. In addition, all clinkers showed satisfactory development of the interstitial phases and low detection of Free Lime crystals, indicating the proper formulation of the flour, appropriate burning and cooling conditions and the deduction that the proportions of Periclase verified may not be harmful to the cements composed by the clinkers obtained. In the face of such verifications, it is estimated that the clinkers developed in this research, based on widely discarded and available material, may form belitic cements, enabling application in large-scale constructions that require low hydration heat and also Portland cements, whose cure is faster and use is widespread.
In reason of the environmental demands linked to the civil construction sector, both with regard to the generation and incorrect disposal of waste and with regard to the large consumption of natural resources and the emission of pollutants linked to the production of cement, the present work consisted of studying the potential increment of the Red Ceramic Waste (RCW) from masonry blocks used in the civil construction sector simultaneously as a pozzolanic addition to Portland cement and also as a raw material to compose clinkers in total substitution to natural clay, due to the similarity of demands chemicals required by the two applications. The RCWs were collected and processed through mills and underwent X-Ray Fluorescence (XRF), X-Ray Diffractometry (XRD) and Specific Mass tests in order to characterize them. Subsequently, the pozzolanic potential of the material was defined from the performance index with Portland cement at 28 days, from the activity with lime at 7 days and verification of the chemical composition, all the results being compared to the requirements determined by the standards NBR 12653/2015 to ASTM C618/2019. For application as a clinker component, the flour was formulated based on the chemical parameters: Lime Saturation Factor (LSF), Silica Ratio (SR) and Alumina Ratio (AR). The flour was subjected to heat treatment at three different temperatures, that went 1300°C, 1380°C and 1420°C. The sintering products were evaluated by means of fluorescence and X-ray diffraction, and the crystalline structure was refined using the Rietveld method, in order to monitor the influence of temperatures on the formation of the phases. The chemical composition of RCW proved to be rich in silica, alumina and iron oxide, which is advantageous for active mineral additions in cement and compatible with ideals for clays that compose clinkers. With the analysis of pozzolanic activity, it was concluded, from a panoramic perspective of its physical and chemical characteristics, that the material showed reactivity in the way it was benefited, and resulted, even, in an increase of 4% of compressive strength in the mortar in which it was incorporated. With regard to sintering products, it was found that belitic clinkers were obtained from heat treatments carried out at 1300°C and 1380°C and Portland clinker at 1420°C, with such conclusions based on the verification of proportional changes between the formation of Alita and Belita crystals in the samples. In addition, all clinkers showed satisfactory development of the interstitial phases and low detection of Free Lime crystals, indicating the proper formulation of the flour, appropriate burning and cooling conditions and the deduction that the proportions of Periclase verified may not be harmful to the cements composed by the clinkers obtained. In the face of such verifications, it is estimated that the clinkers developed in this research, based on widely discarded and available material, may form belitic cements, enabling application in large-scale constructions that require low hydration heat and also Portland cements, whose cure is faster and use is widespread.
Descrição
Palavras-chave
Resíduos de cerâmica vermelha, Atividade pozolânica, Clínquer, Refinamento de Rietveld, Red ceramic waste, Pozzolanic activity, Clinker, Rietveld method