Bad Concrete

toli

i had 650 sq ft about 5" thick of concrete poured.its been over a year now and its still way too soft. i meanvery soft. just walk on it and dust builds up. im very puzzled. i think they just used lime instead of portland. the worst mix i ever saw. i spoke with the contractor who did the job. he pointed to the concrete company. called the concrete company he used. they point the finger to the contractor. probable sprayed too much water on the mix. im lost for word here.

NY Block Head

You can always look up a testing lab. They'll take a sample of your concrete and test it for strength and the ingredients. In my experience, I would say the crete is bad from what your describing. Did you watch the contractor pour? If the contractor was short on help or lazy, he could have had the concrete driver add too much water to bring the slump up to a 9 or 10 (almost liquid w/ stones in it). That could cause bad flaking on the surface. Something to think about.

PipeGuy

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.

Teetorbilt

Waiting a year makes it a little tough to go after anybody.
Maybe you should think about something to lock the surface up before it suffers any more damage. I assume that the slab is ok otherwise, no cracks?

jgriffin22

toli - just a thought I had while driveing thru the pouring rain. Check back and see what the weather was like the day it was poured. An unexpected thunderstorm might possibly have caused your problem.

Teetorbilt

Most pours are covered in plastic during the cure time. Rain may affect areas at the overlaps but not the entire pour.

jgriffin22

Very true Teetorbilt! However, toli did mention that the contractor pointed finger to supplier which did make me think that the possibility of a contractor problem may be high IMHO. Jay

Teetorbilt

We really only have one supplier here and for them to screw up any mix represents WAY too much liabiliy for them, like the building collapse in Hobe Sound. I'm convinced that it's the contractor.

TimWieneke

Wouldn't rain would make the surface pop and look like the moon, not make it dusty....? Not having seen it, if I were to guess I would say it was a bad mix.

Tim

PipeGuy

Dust building up on the surface = 1.) all the sand and gravel was worked out of the surface 2.) there was never enough sand and gravel in the mix or 3.) somehow dirt (mud?) was introduced into the mix.

__________________
Fortunately I keep my feathers numbered for...for just such an emergency. -Foghorn Leghorn

Teetorbilt

Tim, it all depends on how much rain and how far along the set was. Even a short downpour on a fresh pour will wash out the lightest element (cement) and leave the sand behind. Attempting to further work the surface, screed or float, would make the problem go even deeper in the pour.

TimWieneke

Thanks for the clarification Teetorbilt. Now that you've said it, I got to thinking about the few times we've had excess crete left in the rain after a pour. You're right - it gets that soft, sandy surface...