10-29-2012, 06:55 AM
Concrete Delivery Time Study
Author: Vruno, Daniel M | Size: 5.09 MB | Format: PDF | Quality: Original preprint | Publisher: American Engineering Testing, Incorporated | Year: 2011 | pages: 177
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 air-entrained concrete. This 60-minute time limit could unnecessarily increase the cost to construct these bridges. Although other state departments of transportation (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 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. The goal of this project was to utilize the results of the testing programs and develop specification guidelines that allow the implementation of chemical admixtures to extend transport and delivery time from the current 60 minutes for air-entrained concrete up to 120 minutes.
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