New basement bathroom - Bad concrete pour?

[JeffV]

Moving right along on my basement bath project, the last thing I thought I'd screw up was the concrete patch. - I'm not real sure what to do at this point, but I poured 14 bags of 80lb quickrete and one week later, the finished floor surface is rough and gritty. Anytime I walk on it I kick tiny particles of sand. If I sweep it w/ a push broom, cement dust kicks up into the air. I'm thinking I used too much water and/or finish-troughed it too much.

My intent is to tile the bathroom and I don’t want to have bonding issues w/ the mortar down the road. Does anyone know of any products I might be able to put on it to fix the issue? Is the only fix for this to jackhammer it back out and re-pour?

Any thoughts, comments, opinions appreciated…

Thanks - Jeff

[BigBoschMan]

Are you good with a hand trowell?...If so,either do a drymix mortar bed before your tile project or use latex modified thinset to make a smooth surface for your tile.

[harleysilo]

Have you vaccumed it with a shop vac to get all the dust and sand etc. up? To ensure that it just not deteriorating each time you walk on it?

[TedL]

A self-leveling mix might be the easiest route.

[JeffV]

I scrubbed the whole area yesterday w/a very coarse, hard brush (made for cleaning concrete) then took the shop-vac to it. That definitely seemed to make it better in the sense that there is not as much sandy, gritty substance coming off....but it still comes off it you drag your foot accross it while pressing down.

There is definitely some good, hard surface that I think/hope something will adhere to. So are you thinking the latex modified thinset might bond to it OK?

My surface is nice and level w/ the old floor so I don't think a floor-leveler would really work unless I was to take some of the new pour out or just do leveler over the whole floor, a 6x6 area...never used floor leveler...can I do areas that large?

Jeff

[TedL]

6x6 is a small area, and you can put it on in a very thin layer to save material cost.

You could do a whole basement, but that can get pricy.

[JeffV]

That may be my best option then. No drywall or anything up at this point, just framing, so the bottom plate would make a good perimeter to run the leveler up to. Thanks for the reply.

Jeff

[hj]

One problem could be that that concrete mix is often coarse. I often add some Portland to it to make a richer mix.

[geniescience]

Your initial description talked about a problem with dust and grit. I'm not there to see it, but I think that any thinset will stick to it. A latex additive is even better.

If you are happy with the level-ness, you don't need to spend big money leveling it with Self-Leveling Cement (SLC).

Nobody has ever posted about thinset not sticking. Just tile it.

David

[GregO]

As long as the dust/sand/grit stops coming up, I agree that using a high-quality thinset should do very well. Actually, a coarse surface is ideal because it creates a far better mechanical bond.

Greg

[leejosepho]

I poured 14 bags of 80lb quickrete and one week later, the finished floor surface is rough and gritty ...

Does anyone know of any products I might be able to put on it to fix the issue?

I had the same kind of problem when I made a new lid for my septic tank last summer, and in my own case, I believe a weak mix needing more portland, like hj said, was the cause. I would also say you will be just fine finishing it off with some thinset prior to tiling. Or, maybe something like Mapei's compatible "Planipatch" might be a little better if you have to fill 1/4" or more.

[geniescience]

yes, a patching mix (a cement product) or a grout mix (which is also a cement product) will be good.

david
edit: if you are not happy with the surface flatness or if you need to raise the height. Otherwise just tile it.

[JeffV]

Thanks for all the suggestions. You all have been a great help.

I do believe I can get away w/ just tiling over it. At minimum I may have to use the SLC to fill in a couple very small low areas in my pour.

The sand/dust are definitely down to a minimum now and I'm thinking the thinset will bond to it w/o issue. I may even test a small section.

This is truly a lesson learned. I'm just glad it was a small pour. Had I done anything more substantial or needed to have a smooth finish this could have been really ugly.

Thanks again everyone - Jeff

[jadnashua]

Use a long straightedge to determine the extent of the depressions you want ot fill. Thinset can be used up to about 1/4", and is cheaper. You can do it in layers if you let it cure inbetween, too. I'd consider that before I tried SLC (although I've used both). SLC has an extreemely short pot life...you mix it, pour it, and stand back and watch it harden. You have nearly no time to feather the edges, and unless you are covering the whole area so you don't have edges is tough, since determining exactly the right amount to fill in the bowl can be hard, and you have to use it all up and feather edges all in a few minutes. If you try to work SLC once it starts to cure, you will end up with a really big mess. It flows, but when it is thin, you need to move it around to wet the surface, otherwise surface tension will keep an edge; sort of like cold honey - the edge will have nearly a circular shape, not a feathered edge unless you spread it out.

[Bob NH]

There are different grades of SackCrete or QuickCrete.

The least expensive should not be used for any project that requires finishing. It has too much large stone, and too little sand and cement.

Problems with concrete often arise from too much water and too little water.

When it is mixed, the mix should be only as wet as necessary to place and finish it. It should stand in a pile. It should not run. When you are finishing it, you should float up enough fines (sand and cement) to get a smooth surface. If you get a puddle of water when you finish it, you used too much water.

After it sets up and is not susceptible to being washed away, it shold be kept moist. The cement needs water to bind the molecules into what is called a hydrate. Too little moisture, as from low humidity in the winter, prevents curing of the surface.

Concrete should never be allowed to freeze until it is fully cured; at least a couple of weeks.

At this point, you probably need to scrub off the loose stuff and go with a tile set mix that may be used thick enough to give you the spacing that you need. http://www.tileusa.com/thinset-mortar_faq.htm#medmortar

You are not likely to be able to "fix" the problem as good as you can do with a medium bed thinset.