Diagnosing delayed ettringite formation in concrete structures

“…Em (a) e (b) observa-se a matriz formada pelos silicatos hidratados. Em (c) e (d) nota-se a presença de etringita, pois a mesma exibe microestrutura na forma de agulhas [14][15][16]. Essas agulhas puderam ser melhor observadas em ampliações da ordem de 5000 vezes para 1:3, (d), e de 10000 vezes para 1:2, (e).…”

Section: Resultsunclassified

“…Al 2 O 3 .SiO 2 .32H 2 O) [12,13]. A formação de agulhas de etringita começa minutos após a hidratação, e dependendo da proporção alumina-sulfato do cimento, ela pode tornar-se instável e decompor-se formando o monossulfato hidratado, que é mais estável [12][13][14][15][16][17].…”

Section: Introductionunclassified

Efeito do tempo de cura na rigidez de argamassas produzidas com cimento Portland

Garcia¹,

Santos²,

Ribeiro³

2011

Cerâmica

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ResumoO concreto de cimento Portland é um dos materiais mais usados no mundo inteiro, entretanto, devido a sua estrutura ser muito complexa, torna-se imprescindível estudar suas propriedades com bastante profundidade. O concreto é produzido a partir de uma argamassa, de areia e cimento, com adição de agregados graúdos, sendo que suas propriedades estão basicamente suportadas nessa argamassa de constituição. O objetivo deste trabalho foi estudar a variação da rigidez de duas argamassas de composições com razão cimento:areia de 1:2 e 1:3 em função do tempo de cura, tendo como parâmetro a variação do módulo de Young. Os resultados mostraram que o módulo de Young cresce até atingir o valor máximo no oitavo dia, sendo que nos três primeiros dias esse crescimento é mais acentuado. A análise dos resultados indica que grande parte do processo de hidratação do cimento, com formação das ligações químicas responsáveis pela rigidez da argamassa, acontece nos primeiros dias de cura. Palavras-chave: Cimento Portland, argamassa, concreto, cura, módulo de Young. Abstract Concrete produced with

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“…in concretes (e.g. Thomas et al 2008). Furthermore, vaterite -a polymorph of CaCO 3 rarely occurring in the environment -was found in the subsoil of KN5 profile (Table 1, Fig.…”

Section: Mineral Composition Of Wastes and Soilsmentioning

confidence: 99%

Mineralogy and chemical composition of technogenic soils (Technosols) developed from fly ash and bottom ash from selected thermal power stations in Poland

Uzarowicz¹,

Zagórski²

2015

Soil Science Annual

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The aim of the study was to determine the mineral and chemical composition of technogenic soils (Technosols) developed from fly ash and bottom ash from power plants in which bituminous coal and lignite was combusted. The mineral composition of the “fresh” wastes (i.e. fly ash and bottom ash) and soil samples derived from them was examined by X-ray diffraction (XRD) and using a scanning electron microscope (SEM). The chemical composition (content of major elements) was determined using ICP-AES method. Quartz, mullite, and amorphous substances (glass) predominated in the mineral composition of wastes after bituminous coal combustion. Magnetite was also found there. Soils developed from wastes after bituminous coal combustion contained all above mentioned minerals inherited from fly ash and bottom ash. Moreover, small amounts of secondary calcite were identified. In some soil horizons containing large amounts of inherited magnetite, secondary iron oxides and oxyhydroxides (goethite and lepidocrocite) also occurred. Quartz predominated in the mineral composition of the “fresh” wastes after lignite combustion. Relatively small amounts of iron oxides (magnetite and hematite) were also found there. In “fresh” fly ash, apart from minerals mentioned above, anhydrite and calcium oxide (lime) was identified. Soils developed from wastes after lignite combustion contained inherited quartz, magnetite, and hematite. Furthermore, calcite which sometimes was a predominating mineral in certain soil horizons occurred. Moreover, sulphates (gypsum, bassanite, and ettringite), and vaterite (a polymorph of Ca carbonate) were also found in soils. Silicon predominated among major elements in “fresh” ashes after bituminous coal combustion and soil derived from them followed by Al, Fe, K, Ca, Mg, Ti, Na, P, and Mn. On the other hand, the contents of major elements in the samples (ashes and soils) after lignite combustion can be arranged as follows: Si, Ca, Fe, Al, Mg, Ti, K, Mn, Na, and P. However, in some horizons (i.e. in calcareous materials deposited in the topsoil of some profiles) in soil developed on landfills near TPSs combusting lignite, Ca was a predominating element.

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Diagnosing delayed ettringite formation in concrete structures

Cited by 89 publications

References 4 publications

Microscopic examination of deteriorated concrete

Microscopic examination of deteriorated concrete

Efeito do tempo de cura na rigidez de argamassas produzidas com cimento Portland

Mineralogy and chemical composition of technogenic soils (Technosols) developed from fly ash and bottom ash from selected thermal power stations in Poland

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