Client ordered 3000 psi Grout. Project requires 2000 psi. Contractor wants to know if we still have to break the 28 day break eventhough at 7 days exceeds the 2000 psi spec.
What are the unseen potentials with not breaking the 28 day grout samples?
unless the testing company is offering a rebate, break'em.
28-days are considered the legitimate break and the 7-day is considered a diagnostic. Concrete breaks above the specified strength on the 7-day break almost a third of the time in my experience (and usually more so for grout), but the 28-day still gets broken and reported. Besides, if you buy 3000 you should get 3000.
i have heard tales of unstable concrete that gains strength and loses it because of a bad secondary reaction, but whether that can happen b/n 7 and 28-days i don't know.