Concrete Delivery Time Study





1.1 Project Objectives The concrete industry has been asking the Minnesota Department of Transportation (MnDOT) to

lengthen the time allowed to deliver concrete. MnDOT is planning on constructing many small bridge projects that are difficult to reach within the existing 60-minute time limit for airentrained concrete. This 60-minute

time limit may unnecessarily increase the cost to construct



these bridges. Although other state DOTs do allow longer transit

times with the use of retarding admixtures, there are no known studies to

verify whether the longer hauling time is not detrimental to

concrete performance. Also, there may be significant differences in the mix

designs and materials that are used by other state DOTs, as well as the

environments that the concrete is placed and expected to perform in.





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