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Home > Publications > International Concrete Abstracts Portal
The International Concrete Abstracts Portal is an ACI led collaboration with leading technical organizations from within the international concrete industry and offers the most comprehensive collection of published concrete abstracts.
Title: Influence of Cement Composition on Volume Stability of Mortar
Author(s): S. Kelham
Publication: Special Publication
Appears on pages(s): 27-46
Keywords: alkali; clinker; curing; fly ash; mortars; prisms
Abstract:The volume stabilities of mortars have been monitored for periods up to 5 years. In addition to controls maintained at 20°C, prisms were subjected to high temperature curing regimes, typically 12 hours at 70, 80 or 9OO C. Curing temperature was found to be the dominant factor in determining whether significant (>O. 1%) expansion took place during subsequent water storage at 20°C. Most of the mortars expanded after curing at 90°C but very few at 80°C and none at 70°C. Analysis of the results for mortars cured at 90°C indicated that expansion increased with cement fineness and levels of alkali, C3 A, C3 S and MgO and showed a maximum at a cement SO3 content of -4%. The pessimum SO3 content increased with cement alkali content. The incorporation of ground limestone accelerated expansion but did not affect the ultimate value. Cement replacement levels of 30% or 40% with siliceous fly ash and 30% or 50% with ground granulated blastfurnace slag appeared to prevent expansion. A sample of Type IS cement gave only moderate expansion. The mortars that expanded after curing at 80°C had high alkali levels, through the incorporation of KOH or K2 SO4 in the mixing water. At 20°C no long-term expansions were observed, despite the inclusion of cements with total SO3 levels up to 5.6% and clinker SO3 levels up to 2.6%. The Type K cement expanded by -0.05% within the first 7 days and was then stable. Cements based on a high C3 A clinker gave early expansions (-56 days) which increased as the cement SO3 content increased and as the specific surface area decreased, although all expansions were <0. 1%.
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