Effect of Metakaolin on External Sulfate Attack

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Title: Effect of Metakaolin on External Sulfate Attack

Author(s): T. Ramlochan and M. Thomas

Publication: Special Publication

Volume: 192

Issue:

Appears on pages(s): 239-252

Keywords: blended cements; ettringite; gypsum; pozzolans; sulfate attack

Date: 4/1/2000

Abstract:
This paper reports a study on the effect of a high-reactivity meakaolin (HRM) on the sulphate resistance of mortars. Mortar bars containing 0-25% HRM were prepared in accordance with ASTM C 1012-89 with three cements of varying C3A content. After 6 months of exposure to a 5% Na2SO4 Solution, mortar bars incorporating any level of HRM (5-25%) as a partial replacement for a high-C3A cement (~10%C3A) may be considered "moderate sulphate resistant"; mortar bars made with HRM and a moderate or low-C3A cement (<6% C3A) may be considered "high-sulphate resistant". Beyond 6 months, however, it was found that insufficient levels of HRM may, in fact, reduce the sulphate resistance of some cements, and that 15% HRM, or more, may be required for long term sulphate resistance, depending on the C3A content of the cement.