toli said:
...its been over a year now and its still way too soft. i meanvery soft. just walk on it and dust builds up. the contractor who did the job pointed to the concrete company. the worst mix i ever saw.
Can you see sand and/or gravel in it? Is it cracked or spaulding? Is any part of it hard? Was the concrete delivered in a mixer truck? Did you see it poured? Is it reinforced? Was it all poured continuously? What was it about the mix that qualified it as the worst you ever saw?
If too much water was added or applied then the aggregate (sand and gravel) segregates (settles to the bottom) leaving only cement and water at the surface. This will also occur if the pour is "overworked" that is if it is vibrated too much or finished too early. Once the water evaporates then the fine grained cement is left at the top with no coarser aggregates to "bind" together into a hard surface. Many pours have been ruined by the improper addition of water or the lack of proper finishing.
Sometimes suppliers will try to ship several small jobs in one truck, going from job to job and adding more and more water to maintain plasticity, and wind up ruining the concrete that's last out of the mixer. Your pour however was a full load and it's not likely that a ready-mix company would deliver 10+ yards of bad concrete.
It's completely inappropriate for the contractor to "point" to the ready-mix supplier unless you bought the concrete directly. If he's a reputable contractor he should be finding a way to make it right for you.
If it was me, I'd be leaning HARD on the contractor to make this right. I'm certain that the ready-mix supplier is completely off the hook unless cylinder samples were taken when the concrete came out of the truck. You might be able to obtain a delivery ticket for the job from the supplier if you can tell them the date of the pour, the name of the contractor or some other job specific info. With a ticket you can make sure the contractor ordered enough (and didn't have to add something to the mix to "stretcht" it) and see what the mix was. It should have been at least a 3000 psi mix.