Is higher strength concrete more or less prone to cracking?

Question

I am pouring a concrete roof/ceiling over my basement entrance tomorrow (12'x13'). I have the center peaked so the center is much lighter than the outside edges. It will be setting on poured concrete walls. I ordered the concrete earlier today and asked for the strongest concrete they had. One thing led to another & the guy told me he could make 5000 PSI concrete. I didn't even know 5000 existed-I thought 4000 was the strongest (I'm having the structural fiber in it too). I have ALOT of 5/8" rebar ($300 worth) ran in both directions thru the form with ALOT of bracing underneath. Anyhoo, does higher PSI concrete tend to crack more or less then lower PSI crete? Maybe I'm just thinking crazy cause I'm nervous about the pour. I'm thinking maybe it's possible 3000 or 4000 PSI concrete would tend not to crack because it flexes ever so slightly? I don't know... Any concrete gurus please advise. Thanx!

Answer 1

Concrete will do two things. Get hard and crack. The goal is to keep any crack from becoming a break. It sounds like you have taken as many precautions as possible. The 5000 PSI should work just fine for you. Good Luck

Answer 2

Rebar yes...but tie it and space it at no less than 2' both directions.  You should pour it 6" thick if it is a cap over a room and make sure that your supporting scaffold under it is sturdy, if it is has been back filled and compacted then compact it once more before the pour.  The most critical parts are usually the middle and the corners so make sure they have enough re bar there and they are tied well.

Answer 3

doesn't sound that big........so the rebar you have in it should be enough.........as far as the fiber goes........I have a good suggestion where you might put it........but you would dislike the itchy feeling:) I hoped you build a little beam into it....I have done that sometimes and mono pour it.....a like that the best............how thick are you........if you are at least a full 4 you will be find.........I would like 5  ......but.......the steel will do it.........have fun.......wish i was there:)