SPECIAL TOPICS IN CONCRETE PLACEMENT. EXTENDED MIX TIME CONCRETE

The article examines the maximum mix time requirements for concrete. It is noted that quality concrete is now being produced with mix times of 3 to 4 hours, but the industry is still specifiying the traditional one or one and a half hour mix time requirement. The history of this specification is discussed. Examples are given of longer mix times. It is pointed out that it should be included in specifications that mixes can be designed for delivery to project within 3 to 4 hours after the cement and water are mixed if retarders are used, and if the concrete is no higher than 90 F when placed into forms. Admixture research has shown that the initial and final set of concrete can be extended two to six hours from initial set of cement with different dosages of retarder at different temperatures. High-range water reducers can increase the slump at the project site, if required, without changing the water-cement ratios.

  • Corporate Authors:

    American Concrete Institute

    P.O. Box 19150, Redford Station, 22400 Seven Mile Road
    Detroit, MI  United States  48219
  • Authors:
    • Kozeliski, F A
  • Publication Date: 1991

Media Info

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Filing Info

  • Accession Number: 00621802
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Apr 30 1992 12:00AM