New Concrete Getting White Spots

Dec 2, 2015
2
Escondido, CA
Sorry if I am posting this in the wrong place, but our pool construction was just completed this past February, including new concrete around the pool. The pool itself is beautiful and we are happy with it. However, we were initially very disappointed with the concrete because we had requested the concrete color San Diego Buff, which is a pinkish color, but the color ended up being completely gray. The contractor said it ended up with no color because we requested the sanded finish, which hides the color. They said it was our fault for not doing enough research on concrete to know this would happen. We eventually got over that, but then we noticed the concrete had a lot of dark spots on it. The contractor said he couldn't notice them at all and that the concrete looked fine. Well, just in the past few weeks the concrete has started getting white spots all over it. It started out in one area, and then expanded to almost everywhere. Can anyone give me an idea of how this happen? I will try to attach pictures.
 

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Wow, that's a terrible way to treat a customer.

The white stuff is most likely efflorescence. Efflorescence is water permeating up through the concrete and dragging with it minerals from the concrete (mostly calcium). When the water on the surface evaporates away, it leaves behind the minerals. This can happen if the soil under the concrete gets a lot of water in it. The trick to stopping it is to clean it of with a concrete cleaner, such as Prosoco's Safety Klean product. After the efflorescence is cleaned away you have two choices - you can leave the concrete unsealed and see if the efflorescence mitigates over time OR you can seal the concrete with a high quality sealer such as DuPont's Stone Tech Concrete Sealer. Sealing the concrete will make it waterproof BUT it will likely change the color of the concrete and you must reapply the sealer on a consistent basis depending on how much sun exposure it gets (every 2 years is typical time period).
 
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I have a question if you don't mind. Did they cure the concrete in any way? Also, I just want to mention this, not that its a bad idea, careful with sealer on surfaces near the pool. I regret adding it to our stamped concrete. Its very slippery and I worry every time someone takes a run for a jump in the pool. Not all sealers will leave this finish, but I would recommend to apply it to maybe 20 ft^2 first. Otherwise, the sealer might specify its non slippery. I'm looking for excuses to sand blast my decking during the cold weather, but my family aint buying it. :-(, will have to wait till Feb. Anyway, do you recall the curing process?
 
I am not certain that is efflorescence (although it looks like it).

To "effloresce" (I don't think that is a word) their must be a water source ABOVE the surface of the concrete to force the groundwater behind the concrete to the surface. Do you have a retaining wall near there that does not show in the pic? That would explain it.
 
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