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Unread 11-29-2008, 03:55 PM   #1
waj
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Cutback-Ready to give up scraping

I've been reading the posts on cutback removal and have just started to scrape. After over one hour of scraping, I'm going nuts. I'm not trying to be a quick quitter, but I have 180 sq. ft. of concrete slab to do - so according to my calculations, I have about 5 x 40 hr solid weeks of scraping to get half-acceptable results (by measuring "acceptable" by the other posts I've read). And I chose this spot because it appeared to be thinner than the rest of the floor. So I probably have 10 weeks of work. The concrete slab was troweled very rough as you can see- those trowel marks are not the cutback on top the slab, but rather in the slab!

We would like to install tile over this slab and I guess I'm just confused by all the different approaches/answers to handle cutback. I suppose everyone thinks their problem is unique, but it seems like whoever installed this used much more than needed. It's ridiculous. I can say 99% of the adhesive stayed on the floor when the tile was removed.

Any additional suggestions? I appreciate it.
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Unread 11-29-2008, 04:20 PM   #2
Scottish Tile and Stone
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Your saying, the cutback is down inside the trowel marks left by the concrete guys? If so, I would scrape what I can, and get the best thinset money could buy and have at it.
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Unread 11-29-2008, 04:32 PM   #3
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Quote:
Your saying, the cutback is down inside the trowel marks left by the concrete guys?
Yea, that's right.
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Unread 11-29-2008, 05:06 PM   #4
Davestone
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As said, most thinset manuf. have a line that is recommended over cutback, go to their site or read the bags.
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Unread 11-29-2008, 05:14 PM   #5
Jim O'Dell
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I'm a newbee myself, but how deep are the trowel marks? I had paint and stain/varnish on a floor I just finished, and with the help of CX, I went out and bought a DeWalt , probably not the brand of his choice, diamond cup blade for my 4 1/2" angle grinder, and with just a light touch it scraped the entire floor down to the bare concrete in less than an hour and a half. 15 X 13 room plus closet space = about 210 sq feet. Now if you do this, be prepared for dust!! You'll need a very good dust mask, not just the fiber cup that goes over your nose and mouth with a rubber band around the head. A real dust mask. And a big fan to exhaust the dust out the window. I had to stop every 10 minutes to let the dust clear because I could no longer see the floor!! No joke!!
Now, this may not be the right method for you. Lets see if some of the pros think it would work. But if it is a good alternative for you, you will be finished in hours, not days. Just remember the dust will go everywhere. Jim.
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Unread 11-29-2008, 05:33 PM   #6
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I am finishing up a similar situation only my mess was from carpet and twice the size. http://johnbridge.com/vbulletin/showthread.php?t=67581 Cup wheel made great progress. Is the glue still tacky? I got stairs that the glue is tacky still, wheels just gum up. Talked to an old friend of mine who does restoration work come to find out and said if the floor is tacky put flour on it overnight to harden it up. We shall see if he is right tomorrow.
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Unread 11-29-2008, 07:47 PM   #7
uhale
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Hi Walt, I've been dealing with a similar problem floor, although the black adhesive on my floor was much thicker then yours looks. I didn't use a grinder like Tim, and my results aren't as nice, but I think it was good 'nuff. Here's what I did:

1. Sprayed with "Contractors' Solvent" from a spray bottle (I tried maybe 5 different things, this was the only one that worked---it is available at TrueValue Hardware stores or online).
2. Let sit for awhile (10 min), resprayed "dry" spots
3. Go over every square inch with a wire grinder on a drill
4. Pour boiling hot water over small areas (a couple square feet), and grind every square inch again
5. Pour more hot water, and suck up with a Wet/Dry Shop-Vac
6. Repeat until done

Again, this is time consuming, and very labor intensive. If you can handle the dust, a grinder may be the way to go, but keep in mind that many old adhesives have asbestos in them.

Good luck!

Elahu

P.S.--Pic shows new SLC poured on cleaned floor on the left side, and "cleaned" floor on the right.
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Unread 11-29-2008, 08:16 PM   #8
matman
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Walt
Mr cutback is a tough customer. I was working on one a few mos. back. I tried a razor scraper, a hammer gun, a cup diamond wheel and a torch to see if it would burn off. Nuttin. I finally ended up using a dry blade on my angle grinder to scarify it somewhat. When I was done, it looked like 2 to 3 in. squares of scribble all over the black.

I thinset over that with Laticrete 254 and hoped for the best.


Elahu, you shouldn't use chemical means to remove the cutback,the liquids sink into the slab and can prevent a good bond.
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Unread 11-29-2008, 11:11 PM   #9
uhale
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Matman--I was worried about that possibility. I went with chemical removal for a few reasons--1. the black adhesive was very thick in some places 2. the floor needed to be leveled with SLC 3. I did not want to deal with asbestos dust from grinding.

I was able to get most of the adhesive off, and the surface now appears dry and feels like clean concrete. It seems to me that in my case, the chemical removal has worked, and the SLC has bonded strongly. That said, I'll be looking at a thin-set that can be used over mastic.

I'm not that experienced with flooring, and I fully appreciate the professional opinions on this matter. Please take my advice with caution.
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Unread 11-30-2008, 04:29 PM   #10
smarsh
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Remember the asbestos...

I looked for a previous post of mine on this issue and put it below. I hope for your sake that you are aware that cutback adhesive can contain asbestos - mine did. If you're not sure, I highly reccomend getting it lab tested before mechanical removal methods that will contaminate your home.

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I've used a product called Sentinel 747 Adhesive Remover. It takes off the cut back adhesive and leaves no residue. There are critics of this idea saying that it will fill the pores of the concrete. The company says that's not true and in my case that didn't happen. The concrete went from black adhesive to mostly clean white porous concrete. Hard to believe but true.

If you know what your doing and know about asbestos, it can be used quite safely w/asbestos containing adhesive. Again IF you know about asbestos.

Hope that helps!
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Unread 11-30-2008, 06:02 PM   #11
matman
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I am aware of the danger with asbestos Steve. Sentinel 747, I'll research it. If it can live up to its claims I'd say it's some product.To this point I've never heard any praise for a chemical remover however. Thanks for the info.
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Unread 11-30-2008, 09:38 PM   #12
tilelayer
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id get it clean as i can and get some superflex or 254 to set the tiles
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Unread 12-01-2008, 08:18 AM   #13
waj
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Steve,

Quote:
I looked for a previous post of mine on this issue and put it below
How along ago was this? How are the tiles holding? Any issues?

Yea, I'm aware of the asbestos issue from reading previous posts- that's why I have been scraping and not using mechanical removal. I was just thinking last night I should have the material tested so I know how careful I need to be.

Thanks.
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Unread 12-01-2008, 09:16 AM   #14
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Certainly I hope you DO NOT have any asbestos present. Scraping IS a mechanical means and unless the material being scraped is wetted down with (in this case) solvent, scraping may release asbestos fibers if they are there.

As far as my tile adhesion... having started 6.2 million projects simoultaniously, we haven't tiled yet, just have the bare slab in my laundry room. However, most people have said that the water absorption test is the best indicator for adhesion and my floor soaks it up nicely, after using Sentinel.

(put a couple of tablespoons of water on the cleaned concrete and give it 20-30 seconds to start soaking in - if it does, the pores are open)

Some big orange boxes carry it or you can find it on-line.

And NO I'm not a paid spokesman for the company, I took a shot at something against the advice of others and it worked for me, so I'm a believer.

I hope that helps and no... I'm not avail. to scrape your floor...
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Unread 12-01-2008, 09:22 AM   #15
waj
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I did wet the surface down before scraping. As I said in my first post of this tread, I only scraped about one sq. ft. in an hour and a half and have not done any more.

I just spoke to a local lab and am headed over there to get this tested.
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