Estimation of Critical Ettringite Content Due to Sulfate Attack

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Title: Estimation of Critical Ettringite Content Due to Sulfate Attack

Author(s): Ahmed M. Diab, Hafez E. Elyamany, Abd Elmoaty M. Abd Elmoaty, and Ali H. Shalan

Publication: Materials Journal

Volume: 116

Issue: 6

Appears on pages(s): 55-64

Keywords: C3A content; chemical analysis; ettringite; sulfate attack; sulfate ions

Date: 11/1/2019

Abstract:
Sulfate attack on concrete considerably affects the lifetime of concrete structures. The critical content of ettringite at which a considerable decreasing of compressive strength is created in this research. An experimental program on cement paste and concrete was carried out. To accelerate the magnesium sulfate attack, magnesium sulfate salt was added to the paste and concrete at the mixing stage. A theoretical chemical method was suggested to calculate the ultimate ettringite content. The experimental cement paste stage, with 24 mixtures, was tested to verify the results of this method. The ettringite content was measured using X-ray diffraction testing and compared with the theoretical method. Fifteen concrete mixtures were tested to study the effect of accelerated ettringite on mechanical properties and expansion. The studied variables included, C3A contents and relative magnesium sulfate addition. From this study, there is a good agreement between the proposed method and experimental results. The critical ettringite content ranges from 45 to 66 kg/m3 and depends on C3A content.