Back in the day when I tested concrete on-site I had to check the batch tickets for transit time. 45 minutes was the window from plant to pour. Any truck over 45 minutes old was rejected.
Never was a problem except for one job that was deep in a national forest and a hard 45 minutes from the plant.
Had to reject a couple of trucks on that job.
Has concrete technology changed in the past 30+ years that would allow longer batch times?
I wasn’t aware of the strict time constraint. That might require that they cross the top.