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Advisor(s)
Abstract(s)
A deterioração do concreto por agentes químicos ocorre da interação com ambientes agressivos. No caso
dos sulfatos, podem ser originários do solo, das águas agrícolas, da indústria química, da decomposição
da matéria orgânica, dos poços de mineração, de ambientes marinhos e das tubulações de esgoto. Os íons
de sulfato, ao penetrarem no concreto, reagem com compostos hidratados do cimento e formam
produtos expansivos como a etringita e gipsita. Estes produtos, ao se expandirem, causam a fissuração do
concreto, permitindo a entrada de novos agentes químicos. Outras deteriorações sofridas são a perda de
massa do concreto e a perda progressiva de sua resistência. O objetivo deste estudo é avaliar o
comportamento de produtos cimentícios submetido ao ataque por sulfatos. Foram moldados corpos de
prova de pasta de cimento, argamassa e concreto com três diferentes tipos de cimento (CPII-F-32,
CPIII-40-RS e CPV-ARI-RS.). Após moldados os corpos de prova foram divididos em dois grupos: Grupo 1 –
exposição somente à água (câmara úmida); Grupo 2 – exposição à solução de sulfato de sódio (Na2SO4) a
5% à temperatura de 55oC. Para os corpos de prova de pasta de cimento foram medidos, de quatro em
quatro dias, sua variação de massa e de comprimento. Os corpos de prova de argamassa foram avaliados
quanto à variação de massa, resistência à flexão e à compressão, e os corpos de prova de concreto quanto
a sua porosidade, módulo de elasticidade, resistência à compressão axial, resistência à tração por
compressão diametral e homogeneidade. Os ensaios foram realizados após 57 dias expostos à solução de
Na2SO4 a 5%. Em escala microscópica, foram analisados em um Difratômetro de Raios-X (DRX) e em um
Microscópio Eletrônico de Varredura (MEV) para a verificação da formação de etringita e gipsita. Os
resultados obtidos para todas as amostras foram muito similares, porém, para a análise no MEV, foi
possível evidenciar a formação de cristais de etringita e gipsita. Como suas formações foram bem pontuais
e escassas, devido ao período de tratamento no presente estudo, concluiu-se que, em pequenas
quantidades, estes compostos não influenciariam as propriedades mecânicas dos corpos de prova.
The deterioration of concrete by chemical agents occurs with the interactions with an agressive enviroments. In the case of sulfates, it may originate in the soil, agricultural water, chemical industry, the decomposition of organic matter, mining pits, marine enviroments and sewer pipes. When the sulphate ions penetrate the concrete, reacts with hydrated cement and forms expansive compounds like ettringite and gypsum. These produts, as they expand, cause the concrete crack, that allows the entry of new chemical agents. Other deteriorations suffered by the concrete are the weight loss and the progressive loss of its resistance. The purpose of this study is to evaluate the behavior of cementitious products submitted to sulfate attack. Cement paste, mortar and concrete specimens were molded with three different types of cements. After molded, the specimens were divided into two groups: Group 1 – humid chamber curing; Groups 2 – exposure to sodium sulfate solution (Na2SO4) 5% at 55oC. The cement paste specimens were measured every four days to evaluate weight and length variation. Mortar specimens were evaluated for weight variation, bending strength and compression, and the concrete samples were measured as its porosity, elasticity modulus, compressive strength, splitting tensile strength and homogeneity. They were tested after 57 days exposed to the sulfate solution. On a microscopic scale, they were analyzed in a X-Ray Diffraction (XRD) and Scanning Electron Microscope (SEM) to verify the formation of ettringite and gypsum. The results for all the samples were very similar, but for SEM analysis it was possible to demonstrate the formation of ettringite and gypsum. As their formations were well off and scarce, due to the period treatment of this study, it was concluded that in small amounts these compound do not influence the mechanical proprieties of the specimens.
The deterioration of concrete by chemical agents occurs with the interactions with an agressive enviroments. In the case of sulfates, it may originate in the soil, agricultural water, chemical industry, the decomposition of organic matter, mining pits, marine enviroments and sewer pipes. When the sulphate ions penetrate the concrete, reacts with hydrated cement and forms expansive compounds like ettringite and gypsum. These produts, as they expand, cause the concrete crack, that allows the entry of new chemical agents. Other deteriorations suffered by the concrete are the weight loss and the progressive loss of its resistance. The purpose of this study is to evaluate the behavior of cementitious products submitted to sulfate attack. Cement paste, mortar and concrete specimens were molded with three different types of cements. After molded, the specimens were divided into two groups: Group 1 – humid chamber curing; Groups 2 – exposure to sodium sulfate solution (Na2SO4) 5% at 55oC. The cement paste specimens were measured every four days to evaluate weight and length variation. Mortar specimens were evaluated for weight variation, bending strength and compression, and the concrete samples were measured as its porosity, elasticity modulus, compressive strength, splitting tensile strength and homogeneity. They were tested after 57 days exposed to the sulfate solution. On a microscopic scale, they were analyzed in a X-Ray Diffraction (XRD) and Scanning Electron Microscope (SEM) to verify the formation of ettringite and gypsum. The results for all the samples were very similar, but for SEM analysis it was possible to demonstrate the formation of ettringite and gypsum. As their formations were well off and scarce, due to the period treatment of this study, it was concluded that in small amounts these compound do not influence the mechanical proprieties of the specimens.
Description
Keywords
Concreto Ataque por Sulfatos Etringita Gipsita Concrete Sulfate attack Ettringite Gypsum