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.
As ready mixed concrete producers continue to look for ways to lower their environmental impacts, reduction of returned concrete waste is an important opportunity,” says 2020 RMC Research & Education Foundation Chairman Ted Chandler (Chandler Concrete).“This research provides important validation that with technological advances in the production and evaluation of ready mixed concrete, we can and should reconsider arbitrary rules which increase waste and costs without any measurable impact on performance,” adds RMC Foundation Executive Director Julie Garbini.