Quote:
Originally Posted by wamley
27 days after concrete is placed it is at its designed specification. Usually 350 PSF.
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IMHO your quoted compressive strength of 350 psi is off by a factor of 10 for mid range concrete mixes as defined by bags of Portland cement per cubic yard of concrete. From 50 years ago construction and engineering school, basement non load bearing slabs were 2000 psi and highway paving was 5000 psi.
Generally accepted curing rules are that concrete reaches 70 % of its ultimate strength in 7 days and that normal construction activities can continue. In TV you will see that wall block works starts in 2 days typically. The graphs typically show 10% strength gain per day for 7 days in basically a straight line. After that the strength increase rate generally slows down. 28 day strength is typically stated as 90% of ultimate strength. Theoretically concrete continues to gain strength "forever" at a continually decreasing rate but gains less than 10% additional past 28 days.
There is no need to avoid doing some work on the birdcage slab for more than 3 days to 7 days maximum. Generally shrinkage cracking control cuts are made the next day. Starting to drill the holes for attaching the frame can start soon there after. Using machinery to move large loads should wait for 7 days anyway.