Tips for Finishing a Concrete Floor
We’re building a house and were planning on using the concrete pad as our living space floor (no carpet, tile, etc). Any tips on cleaning the concrete before putting the densifier on? We had them covered during sheetrocking, painting etc but there still seems to be a white chalky-ness to them that we can’t seem to scrub through. Is this building dust? Or just the nature of the concrete?? Any tips? Thanks so much!!
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Did you install a liner before pouring the slab?
Hi Steve. Our contractor put down a vapor barrier. I think he used a 10 mm visqueen. My husband wonders if he didn't tape seems or around plumbing.
Steve Knapp's question is a relevant concern regarding the chalkiness, which, according to your description could be effloresence. If there is no liner under the concrete the moisture that may migrate through the slab can carry soluble salts to the surface. Check out this link to the Concrete Network for an explanation and how to address removal.
Thanks for the thought Daniel. I'll check out the link right now. My husband was wondered if it had something to do with some kind of evaporation residue from our fairly-hard mop water.
Really helpful article Daniel! This definitely could be what we're dealing with. I'll pass this post on to my husband and our general contractor. Thanks again for your helpful input!
We poured the concrete on a hot July day. Now it's Dec in NE WA where outside temps have been in the teens to low 30's. Inside we've had heat running steady. Could just the seasonal temp differences be enough to stir up the efffloresce, do you think? That wasn't mentioned in the article (unless I missed it?).
For those interested, this is what we're looking at...
Although there is some evidence that temperature changes can be a factor contributing to effloresence, it's the presence of water that migrates through masonry which carrires the soluble salts to the surface.
With slabs the cause is usually due to too much water being used in the mix. Add to that, if the concrete was not cured properly (often too quickly) it will have much less density making it easier for water migration. If there's no gravel base and no liner, inadequate drainage and the presence of ground water, effloresence may also occur (and continue unless the source of water is eliminated) particularly if proper curing technique wasn't implemented. The addition of calcium chloride to the mix for the purpose of accelerating the setting time of the concrete can also be a factor, but since your pour was done in July it's unlikely that it was used.
The removal of effloresence can range from a hard scrub up to the use of diluted muriatic acid. Muriatic acid is extremely caustic, and even when diluted you'll want to use a respirator. Not a dust mask. It's best to start with the weakest possible solution that will remove the effloresence.
This link provides good info on removal: https://www.concreteconstruction.net/how-to/efflorescence-causes-and-solutions_o
This is such a great topic to explore. Please let us know what you end up doing (you can contact me directly at [email protected]). I'd like to do a post along the lines of "Five Ways to Finish a Concrete Floor"--your experience would be valuable input.
I'll try to remember when we're through...! Would be an interesting article for sure.
Did you say you mopped the floor with clear water changing water when you can no longer see the bottom of the bucket? Yes you may need the change the bucket ever 10 square feet.
Your best advice will come from the manufactures of the product you will be applying.
An acid wash would not be an uncommon manufactures recommendation before product application.
Have you consider applying a stain to the concrete to give it some color? Sawing a lines making 2 or 3 feet squares can be very attractive.
Thanks Walta. We had coloring added at the time of the concrete pour. Our contractor cut lines into it on about a 6'x6' grid.
Not sure how often my husband changed the mop water that day. I was occupying our kiddos. Could be it wasn't often enough... 😋
I would think 3 rounds of mopping will be require.