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Delayed ettringite formation in 4-year old cement pastes
Cement paste prisms (40x40x160 mm) made from portland cement have been cured at 100 deg C for 3 hours, followed by extended water storage at room temperature. Large expansions have been observed after 2.5 years for prisms made with a certain portland cement. BSE (backscattered electron imaging) in a SEM (scanning electron microscope), combined with x-ray microanalysis and quantitative x-ray diffraction analysis, was employed to examine the microstructure, the distribution and the quantity of ettringite formed. Bands of ettringite could be readily observed in a heat cured prism near one of its long surfaces, but not in the central region of the prism. X-ray microanalysis demonstrated that S and Al species, initially dispersed in the outer and the inner hydration products around cement grains during heat curing, diffused from these hydration products during the period of 2.5 to 3.5 years water storage at room temperature to form the ettringite bands. Trends between the occurrence of ettringite bands and paste expansion suggest that a causal relationship may exist between these factors.
Delayed ettringite formation in 4-year old cement pastes
Cement paste prisms (40x40x160 mm) made from portland cement have been cured at 100 deg C for 3 hours, followed by extended water storage at room temperature. Large expansions have been observed after 2.5 years for prisms made with a certain portland cement. BSE (backscattered electron imaging) in a SEM (scanning electron microscope), combined with x-ray microanalysis and quantitative x-ray diffraction analysis, was employed to examine the microstructure, the distribution and the quantity of ettringite formed. Bands of ettringite could be readily observed in a heat cured prism near one of its long surfaces, but not in the central region of the prism. X-ray microanalysis demonstrated that S and Al species, initially dispersed in the outer and the inner hydration products around cement grains during heat curing, diffused from these hydration products during the period of 2.5 to 3.5 years water storage at room temperature to form the ettringite bands. Trends between the occurrence of ettringite bands and paste expansion suggest that a causal relationship may exist between these factors.
Delayed ettringite formation in 4-year old cement pastes
Verzögerte Ettringitbildung in 4 Jahre alten Zementpasten
Yang, R. (author) / Lawrence, C.D. (author) / Sharp, J.H. (author)
Cement and Concrete Research ; 26 ; 1649-1659
1996
11 Seiten, 7 Bilder, 2 Tabellen, 28 Quellen
Article (Journal)
English
Calciumaluminatsulfathydrat , Portlandzement , Dauer , Temperatureinfluss , Rückstreuung , Rasterelektronenmikroskop , Röntgenbeugung , Röntgenfluoreszenzanalyse , Phasenzusammensetzung , Mikrogefüge , Calciumsilicathydrat , Wasserabbinden von Zement , Mikroanalyse , Dehnung , Wärmebehandlung , Rissbildung , Zementpaste
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