The search for the application of alternative materials, that can partially replace cement and increase the service life of concrete structures, is necessary from the environmental and technological point of view. In this context, the partial substitution of cement in concretes by pozzolanic additions can be performed as ternary mixtures, such as the combined incorporation of glass powder and metakaolin, enabling the reduction of cement consumption and the minimisation of the CO2 emissions and the natural resources consumption. Therefore, this research evaluated the incorporation of glass powder and metakaolin in an isolated and combined way, as partial substitutes for cement in concretes. The compressive strength and the chloride penetration resistance were evaluated by means of electrical resistivity, chloride permeability, steady-state chloride migration test and chloride diffusion test, obtaining the diffusivity and chloride contaminated depth by the colorimetric method. The alkali–silica reactivity test was also conducted, because of the alkali content of the waste glass being higher than the standard requirements. It was concluded that the combined use of ground glass powder and metakaolin in concrete allowed the replacement of up to 20% of the cement, promoting microstructural improvements and increasing properties related to durability and compressive strength already available at 28 days. Furthermore, it increased the estimated service life up to five times, working as an alternative for the reduction of cement use and concrete properties' improvement.
The sector of ornamental rocks produces significant volume of waste during the sawing of the blocks and demand to find ways to recycle, given its environmental impact. Considering the possibilities of use of industrial by-products as mineral admixtures, aiming at sustainable development in the construction industry, this paper aims to study the performance of the processing sludge of ornamental rocks and grinding after heat treatment, based on their potential application as partial substitute for cement. The residue was characterized, cast and milled to produce glassy material. Was analyzed the mechanical performance and pozzolanic activity with partial replacement of cement by waste in natural condition and after heat treatment in mortars for comparison. The results were promising, so it was possible to verify that after heat treatment, the treated waste is presented as a material with pozzolanic characteristics.
The main cause of concrete structures deterioration is related to the resistance against the penetration of aggressive agents. Aiming at increase the impermeability and reduce the diffusivity of concrete elements, making it less susceptible to the ingress of chloride ions, the use of crystalline catalyst emerges as a good alternative. Its mechanism of autogenous healing enhances the natural pore-filling process of concrete. The aim of this study is to investigate the influence of the use of crystalline catalyst on the chloride ions penetration and service life prediction of concrete. For the concrete mixtures production, it was used blast-furnace slag blended cement, three different water/cement (w/c) ratios (0.45; 0.55; 0.65), with and without crystalline catalyst, totaling six different mixtures. The concrete specimens were cured in a moist chamber and tested at 28 and 91 days. It was performed tests of compressive strength, rapid chloride permeability (ASTM C1202:12), and silver nitrate colorimetric indicator. The results show that, compared to the reference mixture, the use of crystalline catalyst conserved the compressive strength and reduced the chloride ions penetration up to 30%, increasing service life up to 34%.
INTRODUÇÃOUma das funções do revestimento externo é proteger a edificação contra a ação de agentes agressivos [1]. Desta forma, o revestimento fica exposto a inúmeras solicitações deletérias, tais como variações térmicas, vento, umidade, ruído, chuva, incidência solar, carregamentos estático e dinâmico, impacto e peso próprio. Portanto, as fachadas das edificações, por estarem expostas às intempéries naturais, representam uma das áreas mais deterioradas ao longo do tempo [2]. Assim, é importante entender o funcionamento do revestimento externo e analisar as manifestações patológicas existentes nesses locais, a fim de aprimorar esse sistema e minimizar a ocorrência de problemas. As influências dessas ações deletérias levam à perda de desempenho do revestimento e, consequentemente, da sua durabilidade. Para minimizar esses impactos, são necessárias manutenções e inspeções periódicas, que têm a finalidade de detectar os problemas existentes, estudar as causas e avaliar o estado de deterioração do edifício. Para tanto, é importante garantir que essas inspeções ocorram de maneira adequada, levando em conta o histórico do edifício, para que seja possível entender o comportamento das fachadas e propor melhorias nos projetos, na execução, na utilização e na manutenção delas.As principais incidências patológicas percebidas em fachadas com revestimento cerâmico são, entre outras, desplacamento do revestimento, fissuras e trincas, Santo, Av. Fernando Ferrari 514, Vitória, ES, Brasil 29075-910 clari1512@hotmail.com, geilma.vieira@gmail.com Resumo Este artigo teve por objetivo mostrar a aplicação de uma metodologia para inspeção de fachadas em edifícios, baseada em modelos pré-estruturados. Foram vistoriados três prédios com revestimento externo em cerâmica, totalizando 4958 m 2 de área de fachada inspecionada. Mediante a inspeção visual, realizou-se o levantamento das áreas das manifestações patológicas por região e orientação cardeal da fachada e definiram-se os níveis de degradação. Foram realizados testes de percussão nas fachadas e ensaios de absorção de água e expansão por umidade nas placas cerâmicas. Como complemento, levantaram-se as informações referentes aos edifícios por meio de entrevistas e análises de projetos. Foi elaborada a matriz de correlação anomalias versus causas, que permitiu avaliar a origem dos danos. As anomalias com maior ocorrência nos edifícios foram as manchas e sujeiras e a deterioração nos rejuntes. Constatou-se a influência da cor das cerâmicas e da posição das fachadas no desplacamento. Com base nos ensaios de absorção de água, verificou-se que dois edifícios apresentaram cerâmicas com alto índice de absorção e a análise das regiões de fachadas mostrou que a ausência de juntas foi uma das causas do desplacamento em paredes contínuas e na transição entre pavimentos. Palavras-chave: manifestação patológica, revestimento externo, revestimento cerâmico, inspeção. Abstract This article aimed to show the application of a methodology for inspection of facades in buildings
RESUMONeste trabalho é avaliado o processo de corrosão das armaduras induzido pela ação de íons cloreto em concretos produzidos com adição do Resíduo do Beneficiamento de Rochas Ornamentais (RBRO). No estudo de caracterização, foram avaliadas propriedades físicas, químicas e mineralógicas do RBRO. Foram produzidos concretos com três níveis de relação água/cimento -0,45; 0,55 e 0,65 -e quatro níveis de adição de RBRO -0, 5, 10 e 15%-em relação à massa de cimento. No estado fresco foi avaliada a propriedade de consistência do concreto; no estado endurecido foi avaliada a resistência à compressão axial; as propriedades relacionadas com a durabilidade estudadas foram absorção de água por imersão e fervura, absorção por capilaridade, além de ciclos semanais de indução e aceleração da corrosão por ataque de cloretos e monitoramento do potencial de corrosão. Por último, foi feito o ensaio colorimétrico por aspersão do indicador AgNO 3 a 0,1 mol/L. Os resultados mostraram que a adição de RBRO é vantajosa no teor de 5% de RBRO do ponto de vista da resistência mecânica e de durabilidade frente à ação de cloretos. Palavras-chave: durabilidade de concreto armado; corrosão eletroquímica; potencial de corrosão; método colorimétrico; Resíduo do Beneficiamento de Rochas Ornamentais (RBRO). ABSTRACTThis research evaluates the reinforcement steel corrosion process induced by chloride ions in concrete containing ornamental rock waste (ORW) as mineral addition. Physical, chemical, mineralogical analysis and particle size distribution of ORW were performed. Concrete mixtures were produced with three levels of water / cement ratio -0.45; 0.55 and 0.65 -and four levels of ORW addition -0, 5, 10 and 15% -by weight of the binder. Consistency of fresh concrete and compressive strength of hardened concrete were evaluated; water absorption and capillary absorption of concrete were performed as durability features. The concrete specimens were exposed to wet and dry cycles and corrosion potential monitoring test. Finally, the colorimetric method (AgNO 3 of 0,1 mol/L) was performed. Results show that the 5% ORW content ratio is beneficial to concrete at mechanical and durability perspectives against chloride ion attack.
Defects in the crystalline structure of quartz facilitate the connection with the alkali hydroxides, since under a high alkalinity condition (e.g., in concrete), the Si-O bonds of quartz are easily broken. This study set out to investigate the influence of the deformation structures of quartz on its susceptibility to the alkali–silica reaction. A granite, a protomylonite, and a mylonite were selected for this study. Using optical microscopy, the quartz grains contained in these rocks were quantified and their texture characterized. The quartz samples extracted from the rocks were analyzed by magnetic nuclear resonance, to evaluate their potential for dissolving silica as well as changes in their atomic scale before and after the reaction with alkali hydroxides. These analyses were compared with the results of the accelerated mortar bar test. The study showed that the quartz with intense undulatory extinction and deformation bands denotes the most favorable condition to the development of the alkali–silica reaction. However, on an atomic scale, the slightly deformed grains were highly prone to react. Thus, in a high alkalinity condition, over a long period of time, any quartz tends to develop the alkali–silica reaction, regardless of the deformation degree of the grain.
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