Findings in a Ready Mixed Concrete Research & Education Foundation report support reexamination of the 90-minute delivery threshold in ASTM C94, Standard Specification for Ready Mixed Concrete. The just-released “Impact of Extended Time to Discharge on Concrete Durability and Performance” covers a New Jersey Institute of Technology (NJIT) investigation of concrete specimen freeze-thaw performance and resistivity.
|Investigators behind the “Impact of Extended Time” report recorded negligible deterioration on specimens subjected to 343 freeze-thaw cycles. The 28-page document is posted at www.rmc-foundation.org. The RMC Foundation funded the investigation with the Portland Cement Association. PHOTO: New Jersey Institute of Technology|
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 in most markets.
“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.
NJIT researchers observed acceptable results for all fresh concrete and durability indicator tests on specimens prepared from samples obtained at different times up to 150 minutes. Report authors conclude that the current C94 discharge time limits and specifications are conservative, and based on provisions dating to 1935.
NRMCA PODCAST SERIES SPEAKS TO A/E/C PROS, OWNERS, DEVELOPERS
A new National Ready Mixed Concrete Association podcast will feature experts from design, development, construction and related sectors on the benefits of specifying concrete for buildings and transportation infrastructure. Executive Vice President, Structures and Sustainability PE, SE, LEED AP Lionel Lemay kicked off the series last month discussing issues impacting the concrete and construction industries, including sustainability efforts high among association priorities.
The podcast platform, notes NRMCA President Michael Philipps, “Is unchartered territory for many people in our industry and can bring great value to all types of construction projects—from commercial and residential to paving. Our goal is to educate industry professionals but also to start and engage in conversations that we may not have explored yet. We are constantly evolving and continuing these difficult and thoughtful conversations will lead to better industry practices.”
Executive Vice President Gregg Lewis, AIA, LEED AP and colleagues will target podcast content supporting NRMCA’s Build with Strength coalition, which works with communities, lawmakers, and industry employees to advocate for safer, sustainable building materials, plus the companion Pave Ahead initiative. “Concrete Credentials” is available on Apple Podcast App, Spotify, Stitcher, Google Podcast and other major podcast apps, or streamed at www.buildwithstrength.com/concrete-credentials.