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lizneill38 09-12-2013 07:42 PM

Concrete grinding
We are in the process of tearing up our existing flooring to prep for acid stain. We have the usual carpet glue, a little tile mastic as well as a bit of linoleum mastic.

We are renting a carbide grinder to remove the mastic,ect and then a stone grinder to smooth out the surface. In the kitchen, there appears to be some exposed aggregate, same at the entryway, where the tile was. Would it be possible to grind the kitchen to expose the rest of the aggregate and then stain it like that? I know the stones won't accept the stain, but the surrounding concrete will. If I could grind it to be uniform, I think it may look kinda cool. Same would apply to the entry way. Would the carbide grinder expose aggregate eventually?

Any input would be greatly appreciated.

CallMeVilla 09-12-2013 10:19 PM

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Not my taste. I'd prefer self leveling concrete for an even surface without aggregate then an acid stain and sealer. If you look at commercial applications of acid staining, the floor is always free of aggregate.

Grinding down to the aggregate is "possible" but will you leave a ridge where it transitions to other parts of the house?

Here is how I like acid stained concrete to look ...

lizneill38 09-13-2013 11:24 AM

I like the more uniform look too, but was trying to avoid a complete overlay, since the partial aggregate is only in the kitchen and entry way. The aggregate looks to be used as a patch of some kind. Maybe we will be able to grind it back down to the concrete, but that's most likely wishful thinking... We are working with 1400 sq ft of a very open floor plan. Great point about the ridge, hadn't thought of that. Thanks for your input :) In your opinion, is the carbide grinding and stone polishing a good way to prep the concrete in terms of removing the foreign substance, ect?

CallMeVilla 09-13-2013 12:32 PM

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Hey Liz, you bet. We had to demo 1400 sq ft of Mexican pavers (ugly and dated) which left ridges of thinset across the surface. The grinder we used (looks like a floor polisher) removed every trace of the thinset and took out pre-existing "humps and bumps." Since we were bringing in marble for the new floor, the tolerance had to be withing 1/8" ... and preferably less. Laser testing after the grinding determined the tolerance to be 1/16"

Two men can handle the machine but there is a trick. One man on the handle can actuate the grinder .... but it tends to take off across the floor! By looping the power cord over the motor, you can allow the machine to track naturally, then pull it back using the cord. A little practce and you can systematically work your way across the entire area ... even along straight walls.

Vacuum frequently to check progress and use an 8' straitedge to check for missed spots.
ALSO -- wear ear plugs and good dust masks because this is NASTY work.

lizneill38 09-13-2013 02:57 PM

LOL, so we are going to have to lasso that bad boy. Awesome! Actually sounds like fun. How long did it take to finish the 1400 sq ft? The benefit for us is, the majority of the area was covered with carpet, so it's the glue, drywall and some paint that should come up pretty fast. The dust is what is a little worrying for me, since I have small kids. I should check into the ability of attaching a vacuum to the unit, or would I be able to put water on the floor and still have the machine work to its full potential? I know the slurry would be no fun cleaning, but it would cut down on the dust quite a bit... Thanks so much, I really appreciate your advice!!!:)

nvrfinished 09-22-2013 01:25 PM

When my wife and I epoxied our garage floor we rented a grinder from Home Depot that worked real well. It was basically a floor buffer with an attachment called a Diamabrush. We used the one for grinding the concrete but if I remember, they also had one for removing glue and mastic. I learned about it here from this article. I was happy with the results and it was a one man job.

A question about acid stain - I thought the acid needs to react with the lime that is in the top coat of concrete? If you grind that away, will the stain take? Maybe you should test a small section first to see how it reacts before you grind the whole floor. We are thinking about doing an acid stain in our game room and worry about how well it will take if we grind it.

CallMeVilla 09-22-2013 08:28 PM

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TO: Liz ... It took us 1/2 a day to grind the 1400 sq ft which included break time, lunch, and extensive vacuuming. The dust was horrendous and I changed my dust mask at least once an hour. Don't cheap on the junk hospital masks. Get one with a valve. Wear serious ear protection (I use muffs, not just plugs). Wear eye protection to keep dust out of your eyes because concrete dust is caustic.

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