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July/August 2009
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Admixtures

Shrinkage that occurs during the drying process is a major cause of cracking in concrete. However, the application of shrinkage-reducing admixtures in the field has been yielding positive results, and engineers have realized that the admixtures can be used to mitigate cracking.

A new ASTM standard currently being developed by Subcommittee C09.23 on Chemical Admixtures will set minimum standards for an admixture to be sold as a shrinkage reducer. ASTM WK23938, Specification for Shrinkage Reducing Admixtures, will be helpful to users by providing them with assurance that an admixture meeting the standard is not harmful to concrete properties and significantly reduces shrinkage under controlled conditions.

”The primary users of the proposed standard will be owners, specifying engineers and concrete producers,” says Neal Berke, research and development fellow, W.R. Grace & Co., and chair of Task Group C09.23.04 on Durability Enhancing Admixtures. Berke also notes that contractors might use WK23938 as a means to increase joint spacings or to reduce cracking under the same conditions to minimize repair work.

Subcommittee C09.23 is under the jurisdiction of ASTM International Committee C09 on Concrete and Concrete Aggregates. Berke says that all interested parties are invited to participate in the work of the section.

“Once WK23938 is complete, we will be looking into other durability enhancing admixture specifications, as well as incorporating new test methods into existing specifications, if warranted,” says Berke.

CONTACT

Technical Information: Neal S. Berke, W.R. Grace & Co., Cambridge, Mass.

Phone: 617-598-4827

ASTM Staff: Scott Orthey

Phone: 610-832-9730