Floor psi?

[nonhog]

I am still lift shopping.
Most 2 post ask for 4" pad and a certain psi.
My contract doesn't mention psi.
Any thoughts on determining that after the fact?

[slip knot]

Most redimix plants mix a design minimum. see if your contractor can find out where it came from. This may give you a minimum. My slab was poured at a higher psi so they could wreck the forms off sooner.

[DeadNutz]

Go with what SlipKnot said. I believe the minimum psi is 2500 but may be much higher. Less water in the mix generally means higher PSI which allows for faster finishing plus you can strip the forms off quicker. I specified 6-8" thick and higher psi on our shop floor.

[nonhog]

I will check around. My contractor went belly up so I can't ask them.
But shouldn't be too hard to find who they used.
Thanks

[highland512]

If I had to guess its 4000 psi, thats a pretty standard side walk/slab on grade mix design. Did you get any copies of concrete tickets? If you really need to know the psi of your existing slab you could core a cylinder and send it off for break test.   

A 4" slab seems light (thin) for a lift. I wouldn't trust it with out footer under the post with rebar. 

[Uncle Buck]

The best person to talk to is the batch plant operator at the ready mix company supplying the concrete. Depending on what is needed most of them have different recipes for the mixes they make. I worked for a concrete company a few years ago. The batch man is the guy actually mixing the ingredients. Tell the guy what you are doing and he can tell you what you need.

[mrchuck]

Using Portland Cement, the ASME rating is a 6 sack mix for 3000 psi rating tested after 30 days in the test cylinder.
In my earlier career, I tested thousands of cubic yards of concrete on Federal Construction sites.