Bricks, Masonry, Asphalt and Concrete - Concrete patio that never dry's?

Hi we have a concrete patio that was laid last Sept 04. We did have a very wet winter and spring, however it is now up in the 80's and 90's and parts of the concrete still look like they are not dry. Our installer claims that they have still not dryed out. We think he goofed when laying the concrete and that it is stained. There are large dark area's and then very light area's. We don't know what to do?? How do we fix it if it was done wrong? Thanks in advance. Gina and Jack

You have heard the saying "watching concrete dry". Thats because it does take along time. Sometimes a year or more. It does depend on many things, and your contractor may be right. There is another reason however. It could be that when the concrete was mixed at the plant, they had to add cement to the hopper which was a darker color. This is not a contractor problem. However, the concrete company is not going to admit, and there is really no way to prove it. That is just how it is. One thing you could do, is to give your a coat of concrete colored stain then it would all be the same color. Just some thoughts. Good Luck

I saw on the history channel that some of the concrete in Hoover Dam is still not cured. I agree with Jack, if it doesn't go away with time use a concrete stain. :)

Concrete does not dry out - it cures. You usually get 90% of the curing in a month depending on the weather and admixtures. Fly ash additives slow curing significantly.

You are going by what you see and not what you have. You are looking at the surface, which gives you some clues. I assume you had concrete delivered and not mixed on site. Mixing concrete batch after batch for a slab on site is suicide if you are concerned with durability and unformity.

With something as small as a patio it is extremely improbable if not impossible to get two different cements in one batch. If you got central mixed concrete (mixed at the plant and agitated in the truck) you got completely mixed, uniform concrete. If you got transit mixed concrete (mixed in the truck) is still was probably uniform mixed. Since you have an inconsistancy problem, the cause probably came after the truck arrived.

Did you have uniform soil conditions (moisture and absorption) in the area of the patio? Clay or plastic in one area and sand in another area will lead to wide variations in color, durability and curing.

Was water added at the site? Adding water is a sure fired way to get improperly mixed concrete quickly. It also gives you and lower strength, different colors and lesser durability.

Was all the concrete finished the same amount of time after it was poured? If you had two loads the concrete from the second load was probably finished too soon. This is why you wany enough smart bodies around to finish concrete when it is time to finish it. Finishing too early can lead to all kinds of problems.

Did the contractor cover the concrete with plastic after finishing it?

Did the contractor spray a curing compound on the concrete the next day to keep the water in and prevent the surface from curing too fast? No curing compund and concrete that has wet and dry areas can lead to a strange appearance that takes a long time for the appearance to go away. The concrete that was placed too wet will never go away unfortunately.

Ask the contractor to answer these questions and see what he has to say. If he double talks ask if he is licensed, bonded and insured. Then ask him what he proposes to do.

Call the concrete supplier and tell them to come out and look at what their concrete looks like when placed by the contractor you hired. They will be able to recognize how the concrete was placed and finished.

If there realy is a problem you should be able to get some satisfaction far beyond spraying on a pretty stain that may last a little while.

Dick

Thanks for your replies. THe cement was poured on site by our contractor. THe stain as I understand it was added to the concrete mixer. The contractor states "he followed" the directions exactly. It should be noted that our concrete moe strips were installed seperately using the same color and they came out perfectly. I do not see a way to attach photo's to this e-mail or I would.

What has been recommended by a few others is to do a wash with muriatic acid and then ammonia, power wash, and then apply a stain, followed by the sealer. No the concrete was not covered with plastic, and no sealer was applied to my knowledge. THe contractor apparently had only a "busness license" not a contractors license

Since the slab has had time to cure and you are unhappy with the appearance, something should be done. After thins long, it is not likely that it will appear much better. The only thing that bothers me is the quality of the concrete - only time will tell.

When you say the contractor poured the concrete on the site, I assume you meant he mixed it on the site and added the coloring agent. If this is the case, there is not a concrete supplier to rely on. We also do not know what was added as a coloring material. Stains are not used. The only recommeded material to use is an iron oxide pigment, but we don't know if too much or too little was added. That leaves us with the contractor, who seems to playing innocent. If he is not a licensed contractor and is not bonded or insured the odds are low on getting him to correct the problem.

Without looking at the slab, the suggestions you have are a reasonable approach. After you get done with cleaning, there will be a color difference. The stain should mask the variations somewhat. Before applying a sealer (go to a local concrete or building materials supplier) try several small areas that have different conditions to see how they react after a week of aging. You may also contact a landscape dealer or installer that uses concrete pavers. He may also have a suggestion since there are sealers for both indoor and outdoor paver installations, with varying degrees of gloss or sheen.

Good luck!

Dick