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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: Effect of Metakaolin on Alkali-Silica Reaction (ASR) in Concrete Manufactured With Reactive Aggregate
Author(s): G. Vivian Walters and Thomas R. Jones
Publication: Special Publication
Appears on pages(s): 941-954
Keywords: alkali-silica reactions; calcined clay; concretes; expansion; metakaolin; pozzolans; Materials Research
Abstract:A recent report claimed that ASR expansion was suppressed when calcined clay was added to concrete used in hydroelectric dam construction containing reactive aggregates. The authors report a laboratory study on the effectiveness of metakaolin in preventing ASR. Samples of metakaolin were prepared by calcining china clay (relatively pure kaolin) and several ball clays, all collected from Southwest England. Compression cube strength tests were carried out in which part of the cement content of a 1:6 mixture of aggregate and ordinary portland cement (OPC) was replaced by calcined clay. Results showed that some of the mixtures containing calcined clay exhibited no reduction in the 28-day compressive strength, even when 25 percent of the OPC was replaced. Tests for ASR were conducted using prisms produced in accordance with the Draft British Standard 812, Part 123, containing highly reactive natural aggregates that expansion of 0.450 percent at 12 months. Prisms in which up to 25 weight percent of the OPC was replaced by calcined clay have been monitored over a period of 18 months and have shown no expansion or deleterious surface appearance. As a result of these tests, it is concluded that expansion due to ASR is completely suppressed when sufficient metakaolin is added to the concrete formulation. Metakaolin does not reduce the ultimate compressive strength of the concrete, provided that the feed clay is relatively free of impurity minerals.
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