RESUMO O estudo dos parâmetros reológicos das pastas cimentícias pode fornecer informações importantes sobre o desempenho dos concretos frescos nos quais elas serão aplicadas. Nesse contexto, este trabalho visa estudar os efeitos da temperatura nos parâmetros reológicos de pastas cimentícias aditivadas com superplastificantes. Também é abordada a análise do efeito do tipo de cimento, bem como o estudo da ação de superplastificantes à base de policarboxilato considerando sua função e os seus teores na mistura. As pastas foram avaliadas pelo ensaio de mini-abatimento e os parâmetros de tensão de escoamento, viscosidade plástica e indicador de tixotropia foram estimados a partir do ensaio de reometria rotacional e aplicação dos modelos de fluidos de Bingham e Herschel-Bulkley. Os resultados indicaram que o aumento da temperatura levou a uma redução das tensões de escoamento, viscosidades plásticas e tixotropia das pastas. Efeito semelhante ocorreu após o incremento do teor de aditivo até a dosagem de saturação. Para as formulações com o aglomerante de maior teor de pozolana as tensões de escoamento e viscosidades plásticas foram superiores em até 80 e 70%, respectivamente. Os dados reológicos indicam que aditivos de diferentes funções (abertura, espalhamento e multifuncional), embora apresentem a mesma base, influenciam de forma distinta os parâmetros reológicos e plasticidade das pastas cimentícias.
No research demonstrates the effect of combined waste raw materials as an alternative to natural sources in Limestone Calcined Clay Cement (LC3). In this context, this study aimed to evaluate the influence of the composition of ternary cements (TCs) containing industrial waste on their rheological and hydration properties. As raw materials, Portland cement and clay brick (CBW), clay tile (CTW), marble (MW), and phosphogypsum (PG) wastes were used. The rheological behaviour of the pastes was analysed by the mini-slump evolution over time and rotational rheometry. Hydration was evaluated by isothermal calorimetry and XRD/Rietveld. An increase in the specific surface area enhances the yield stress and plastic viscosity of the paste. CBW and CTW have pozzolanic reactivity, presenting an increase in the content of non-crystalline phases, including calcium silicate hydrate (C-S-H). The TCs reached at least 70% of the compressive strength of theHigh Early Strength Portland cement paste.The results suggest that CBW, CTW, MW and PG can be used as an alternative to reduce the clinker factor and decrease the environmental and economic impacts associated with extracting natural raw materials for cement production.
Despitethe increasing number of publications on residual raw materials as supplementary cementitious materials (SCM), the milling beneficiation process and its parameters have been underexplored and presented. In this context, this study aims to evaluate the milling parameters for marble, clay tile, clay brick, and phosphogypsum waste processing for recycling as SCM. The raw materials were benefitted by grinding, sieving, and milling in a planetary ball mill, varying the time and rotation speed parameters. The waste was characterised by helium gas pycnometry, DSC, BET specific surface area, XRF, TGA, and XRD/Rietveld. Waste materials in which the mineral composition of phases was formed at higher temperatures were associated with higher demands for specific milling energy and lower grindability indexes. Marble waste (MW) has a mineral composition similar to commercial limestone and phosphogypsum (PG) can be an alternative to natural gypsum in cementitious materials. Clay brick waste (CBW) and clay tile waste (CTW) have the potential to be used as SCM to replace calcined natural clays, although CTW requires higher energy during milling processes.
Ciência -Estudo e ensino -Brasil. 2. Ciência -Aspectos sociais. 3. Ciência -Política e governo. I. Dalazoana, Karine. CDD 303.483 Elaborado por Maurício Amormino Júnior -CRB6/2422 O conteúdo dos artigos e seus dados em sua forma, correção e confiabilidade são de responsabilidade exclusiva dos autores. 2018 Permitido o download da obra e o compartilhamento desde que sejam atribuídos créditos aos autores, mas sem a possibilidade de alterá-la de nenhuma forma ou utilizá-la para fins comerciais. www.atenaeditora.com.br
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