Long-Term Expansion of Mortars and Concretes


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Title: Long-Term Expansion of Mortars and Concretes

Author(s): C. D. Lawrence

Publication: Special Publication

Volume: 177


Appears on pages(s): 105-124

Keywords: cements; concretes; curing; ettringite; expansion; mortars; prisms

Date: 1/1/1999

The mechanical consequences of delayed ettringite formation (DEF) have been monitored for specimens stored under water at room temperature after undergoing different initial curing regimes, including some designed to simulate practical steam curing. Factors investigated were cement composition, water-cement ratio, and aggregate type. The data show a correspondence between the patterns of expansion shown by mortars and concretes, for the range of portland cements examined. Storage periods have now been extended to over 6 years, and very late expansions are revealed for certain concretes, including those containing limestone aggregate. The possibility that an accelerated mortar-prism test can be devised to predict expansive behavior for practical concretes has been considered: it appears that testing for between 6 and 12 months may be necessary before useful predictions can be made from mortar prism expansions. Mechanisms for expansion due to DEF are discussed in the light of the laboratory findings reported.