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According to Terry Murphy, quality control manager at Meyer Material Co., Des Plaines, Ill., retarding admixtures are not always required during the summer months. Retarders only add to finishers' waiting time when used for concrete flatwork placed in a cool environment such as a basement. Another job that does not require a retarder is short-haul concrete that will be placed quickly because cross-sections are relatively large. Appropriate jobs for retarders during summer months include long hauls, small pours that include significant truck waiting time and jobs which use fast-setting concrete placed with a slow pour rate. Finally, the type of customer may dictate use of retarders. Residential concrete contractors' crews, for example, are often undermanned on driveway and garage-floor pours. KEYWORDS: hot weather, retarder