Update: I didn't believe the precast supplier about their 28 day cure times, I was wrong
Six months ago we poured a 40,000 sq ft deck in Houston using a new precast supplier and I pushed hard to add two extra weeks to the schedule because I figured their cure claims were sales talk. The supplier rep, a guy named Dwayne, told me flat out that if we hit 4,000 psi at 7 days and kept moisture blankets on, we'd be fine, and he offered to eat the cost of any failed break. We did three cylinder tests and all three came in over 5,200 psi, and we saved 11 days on the critical path. Now I want to know if anyone else has run into a supplier who actually backs up their numbers with their own money, or did I just get lucky?