Concrete curing time question...?

Question

What percentage of concretes final strength does it acquire after a week? I know it gains 95% after 28 days but maybe it has 80% after 7 or 8 days? Reason for asking is I built a form for my basement entrance's roof/ceiling and all the bracing and the form itself is in my way and I can't work on anything else till it's outta my way. The crete I used is 5000 PSI with structural fiber and LOTS & LOTS of 5/8" rebar. Any concrete gurus please advise. Thanx!

Answer 1

it going to depend on the thickness of your concrete but as a rule of thumb it will ascertain 75% of it's strength in 7-9 days you can remove your form's and continue with your work be cautious working with it if your setting anchor bolts etc.---do not use heavy machinery around the opening --if your in dought as to it's integerty then work else where on the building---items-- was it viberated into place will determen whether or not you should remove the form's--consistency of pour--once more if your in dought--refrain from removial of the form's and work else where on the building----

Answer 2

You can strip the form immediately after it' sets up- a good idea if you want to dress it up a little where its' more visible. Unless its' a slab you can begin to add weight to it almost immediately but not in the several ton range for at least a week or two- remember concrete is overkill anyway unless it structural,at least strip the form the next day or some boards might get stuck and that's a pain. If it' holding up the first floor wait  3-4 days, if anything cracks then you've done something wrong anyway.

Answer 3

With a 5000 mix I let semi's drive over in 3 days.

At 7 days you should be within 60% of design strength with that hot of a mix.I let people walk on my pours in 2 days with a 3000 mix.When I do drives/sidewalks I pour and strip forms on same day.

Commercial contractors often,often, pour one day and strip the next.My guess is with what you poured if you cored it at 2 days (missing rebar) it would break at 8000 psi.

Call your supplier's quality control and ask them,these are design mixes and they have a performance chart with each mix.

My Best