After many years of research, we were able to validate that the discharge time, up to 150 minutes, had no significant impact on the fresh properties, hardened properties (i.e. In line with the global movement to reduce greenhouse gas emissions and to combat climate change, our research team ( Mohamed Mahgoub, PhD, PE, FACI, Ahmed Omran, Ph.D., P.Eng, Mohab Hussein, MSCE, PE, PMP, and Mohamed Hassan, MSCE) along with the concrete and construction industry collaborators took upon the challenge to tackle this issue. As traffic and road congestion in urban environments have gotten progressively worse, this outdated antiquated rule has unnecessarily increased construction and demolition waste, amplified greenhouse gas emissions, and enlarged the construction cost to the suppliers and contractors and subsequently their clients. This globally enforced 1935 rule requires the completion of concrete discharge within 1ВЅ hours after the introduction of mixing water to the cement and aggregates, or the introduction of the cement to aggregates. One of the main factors for rejecting a great number of truckloads of concrete every year the time limit restrictions, specified by ASTM C 94, Specification for Ready Mixed Concrete RMC.

This waste is expected to increase as we increase the use of concrete to repair our aging infrastructure. Every year, a substantial amount of ready-mixed concrete is returned to concrete plant for disposal. Concrete alone accounts for 8% of global carbon emissions.

Astm c94 90 minutes