Findings in a new RMC Research & Education Foundation report, “Impact of Extended Time to Discharge on Concrete Durability and Performance,” support reexamination of the 90-minute delivery threshold in ASTM C94, Standard Specification for Ready Mixed Concrete.

The report covers a New Jersey Institute of Technology (NJIT) investigation of concrete specimen freeze-thaw performance and resistivity. Authors link the C94 discharge time limit to rejected loads that contribute—along with left over mixes returned to plants—to a waste stream estimated at 3 percent of the industry’s annual volume. The 90-minute window, they contend, becomes more difficult to abide as traffic congestion increases.

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