Influence of weathering of iron sulfides contained in aggregates on concrete durability

Chinchón, J. S.; Ayora, Carlos; Aguado, Antonio; Guirado, F.

doi:10.1016/0008-8846(95)00119-w

Cited by 60 publications

(29 citation statements)

References 7 publications

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“…The most frequent cause is the alkali-aggregate reaction (AAR) (Stanton 1942;Hobbs 1988;Mehta and Monteiro 2006). Hence, the majority of reported dams with expansive reactions found in the literature are related with AAR (Shayan 1988, Regamey and Hammerschlag 1995, Ulm et al 2000, Saouma et al 2007, even though several cases were reported on internal sulfate attack (ISA) (Chinchón et al 1995, Ayora et al 1998, Oliveira et al 2013a, Oliveira et al 2013b, Oliveira et al 2014, Ikumi et al 2014, Chinchón-Payá et al 2015 and alkali-carbonate reaction (ACR) (Neville 2004, Blanco et al 2015.…”

Section: Introductionmentioning

confidence: 99%

Structural Diagnosis of a Concrete Dam with Cracking and High Nonrecoverable Displacements

Campos

López

Blanco

et al. 2016

J. Perform. Constr. Facil.

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Expansions in concrete dams may be caused by chemical or physical sources; however in certain occasions the evidences observed in the dam may not be attributed to a single cause. Mequinenza is an example of a concrete dam affected by expansions and high non-recoverable displacements that cannot be explained by the most frequent pathologies. This paper presents new hypotheses that could justify such behavior by assuming the superposition of a global phenomenon of water induced expansion in concrete in the entire dam and a localized effect consisting in the opening of cracks in the construction joints located in one of the blocks. This is validated by conducting numerical analyses through 2D finite element models that consider the nonlinear behavior of the construction joints and use zero-thickness interface elements to simulate the potential cracking planes in the dam. The results confirmed the diagnosis proposed and the capability of the model to reproduce the behavior of the dam, revealing the significant contribution of the opening of the cracks to the non-recoverable displacements in the dam.

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Section: Introductionmentioning

confidence: 99%

Structural Diagnosis of a Concrete Dam with Cracking and High Nonrecoverable Displacements

Campos

López

Blanco

et al. 2016

J. Perform. Constr. Facil.

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“…The final aggregate size distribution obtained from crushing procedure and used in the mortar production are shown in Table 1. The aggregate density was determined in accordance with NBR NM 52 (ANBT, 2009) [15]: the measured value was 2.81 g/cm 3 . Aggregate water absorption, determined according to NBR NM 30 (ABNT, 2001) [16], was equal to 1.67 %.…”

Section: Aggregatesmentioning

confidence: 99%

“…Aggregates containing iron sulfides were used in Graus and Tavascán dams in Spain in 1992, as well as in buildings in Maresme also in Spain in 1970. Chinchón et al [3], Ayora et al [4] and Araújo et al [5] reported serious concrete cracking and degradation in all the above-mentioned structures. To investigate further this pathological phenomenon, these authors carried out microscopic tests in extracted samples from these structures and found compounds different from those usually produced in the cement hydration of cement.…”

Section: Introductionmentioning

confidence: 99%

Evaluation of pyrite and pyrrhotite in concretes

Marcelino

Calixto

Gumieri

et al. 2016

Rev. IBRACON Estrut. Mater.

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ResumoIt is well known that aggregate characteristics can intensively interfere in concrete behavior especially when sulfides are presented in the aggregates. The lack of consensus to content limit value of these deleterious sulfur compounds in concrete structures for dams has motivated several investigations worldwide. Within this scenario, this work presents a methodology to evaluate the presence of pyrite and pyrrhotite in concretes produced with aggregates containing sulfides. For the study, rock samples from the Irapé hydroelectric power plant area in Minas Gerais (Brazil) were used. This plant was built in a geological site where the rock presented sulfide levels of at least 3%. These rock samples were first ground and then used as aggregates in mortars, which were, during almost one year, subjected to three different exposed conditions: temperature of 23° ± 2°C and relative humidity of 95 to 100%; calcium hydroxide solution diluted in water kept at two different temperatures: room temperature and 50° C. The presence and amount of pyrrhotite were obtained from a leaching process of the material (aggregate or mortar) in a solution of hydrochloric acid. This procedure allowed also the evaluation of the pyrite content. The results showed that the amount of pyrite has remained virtually constant over time in the three exposure situations. This finding indicates that sulfur limits in aggregates should be set according to the type of iron sulfide presented and not solely by the total amount of sulfur.Keywords: sulfide aggregates, concrete, behavior, dams.As características dos agregados podem interferir intensamente no comportamento do concreto, especialmente quando sulfetos, como pirita e pirrotita, estão presentes nos agregados. A falta de consenso para o valor limite do teor desses compostos de enxofre em estruturas de concreto de barragens tem motivado várias investigações em todo o mundo. Dentro desse cenário, este trabalho apresenta uma metodologia para a avaliação da presença desses compostos de enxofre em concretos fabricados com agregados contendo sulfetos. Para o estudo, foram utilizadas amostras de rochas da área de usina hidrelétrica do Irapé, em Minas Gerais (Brasil). Esta usina foi construída em um sítio geológico onde a rocha apresentava níveis de sulfeto de pelo menos 3%. Essas amostras de rochas foram moídas e depois utilizadas como agregados em argamassas submetidas durante aproximadamente um ano a três diferentes condições de exposição: temperatura de 23° ± 2ºC e umidade relativa de 95 a 100%; solução de hidróxido de cálcio diluída em água mantida em duas temperaturas diferentes: temperatura ambiente e 50°C ± 2ºC. A presença e quantidade de pirrotita foram obtidas a partir de um processo de lixiviação do material (agregado ou argamassa) numa solução de ácido clorídrico para dissolução desta, o que permitiu a avaliação do teor de pirita, sulfeto esse não dissolvido pelo ácido clorídrico. A quantidade de pirrotita foi obtida pela diferença entre o valor inicial de enxofre total da amost...

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“…Sua presença pode ser verificada com a evaporação da água, provocando a precipitação de sulfatos hidratados na forma de eflorescências brancas superficiais [10].…”

Section: Introductionunclassified

Avaliação não destrutiva do ataque interno por sulfatos em testemunhos de CCR de uma barragem

Goto¹,

Medeiros

et al. 2017

Simpósio Paranaense De Patologia Das Construções

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Resumo: A presença de íons sulfatos ( 4 2− ) no interior da matriz cimentícia de concretos pode dar origem a um tipo de ataque interno, resultando na sua deterioração ao longo do tempo. Estes íons podem reagir com os álcalis do cimento, formando compostos como a gipsita, etringita e outros sais de sulfato, com características expansivas. Este ataque pode provocar novas reações químicas, alterando as propriedades físicas e mecânicas das estruturas de concreto. Assim, o presente trabalho teve como objetivo avaliar o comportamento físico e mecânico de testemunhos de concreto compactado a rolo (CCR), extraídos de uma barragem de usina hidrelétrica com sinais de manifestação patológica de ataque interno por sulfatos. Após a inspeção visual das estruturas, foram selecionados os locais para a extração dos testemunhos e a realização dos ensaios de resistividade elétrica e resistência à compressão axial. Resultados diferentes foram obtidos no bloco 22, com baixos valores de resistividade elétrica e altos valores de resistência à compressão axial, apresentando picos de thenardita e gipsita pela análise por DRX. A correlação linear R² de 0,85 entre os ensaios demonstrou a sua efetividade na detecção do ataque interno por sulfatos em testemunhos de concreto. Esse trabalho foi desenvolvido no âmbito do Programa de P&D ANEEL, projeto 6491-0301/2013. Palavras-chave: ataque interno por sulfatos, ensaios destrutivos, ensaios não destrutivos, concreto compactado a rolo (CCR)Abstract: The presence of sulfate ions ( 4 2− ) inside the cementitious matrix of concrete can originate a type of internal attack, resulting in its deterioration over time. These ions can react with alkalis of the cement, forming compounds such as gypsum, ettringite and other sulfate salts, with expansive characteristics. This attack can cause new chemical reactions, changing the physical and mechanical properties of concrete structures. Thus, the present work had the objective to evaluate the physical and mechanical behavior of rolled compacted concrete (RCC) cores, extracted from a hydroelectric power plant dam with signs of pathological manifestation of internal sulfate attack. After visual inspection of the structures, there were selected the sites for the extraction of the cores and development the tests of electrical resistivity and axial compressive strength. Different results were obtained in block 22, with low values for electrical resistivity and high values for axial compressive strength, showing thenardite and gypsum peaks by XRD analysis. The linear correlation R² of 0,85 between the tests showed its effectiveness in the detection of the internal sulfate attack in concrete cores. This work was developed under the ANEEL P&D Program, project 6491-0301/2013.

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Influence of weathering of iron sulfides contained in aggregates on concrete durability

Cited by 60 publications

References 7 publications

Structural Diagnosis of a Concrete Dam with Cracking and High Nonrecoverable Displacements

Structural Diagnosis of a Concrete Dam with Cracking and High Nonrecoverable Displacements

Evaluation of pyrite and pyrrhotite in concretes

Avaliação não destrutiva do ataque interno por sulfatos em testemunhos de CCR de uma barragem

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