Asphalt based adhesive residue

[Rob Z]

Hi John,

I recall some discussion in the earlier forum of setting tile over "blackjack", the asphalt based adhesive used for many years to set the non-ceramic floor tiles that were installed by the millions all around the country. These old tiles and the adhesive frequently were laden with asbestos.

I have a job coming up where the customer needs tile set on the basement slab, and the entire surface is coated with 50+year old blackjack. What has been your experience dealing with this stuff?

Shot blasting isn't going to be an option. Nor is a floating mud bed (floor drains and toilet flanges are already set). The original tilesetter dumped some SLC in the bathroom, and it is already coming to pieces. I don't know if this is because he failed to use a primer, prep the surface correctly, or because of the asphalt residue.

My customer has already bought the tile, and wants it installed. I want to do it with the method that's going to give the best chance for lasting for many years.

Rob Z

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[Bri]

Hi Rob
I recently rented a floor grinder at my local rent-all that ran on 110, and it worked really good. I ran around the 1200 sq ft of "blackjack" for a couple of hours(using sandblasting sand as extra help for the grinding stones)and it removed about 75% of the old glue. I wet down the silica sand, so there was virtually no dust. I would have used my terrazzo grinder, but there wasn't enougth power, so I was happy to find this 110 grinder. You might want to try this if you are concerned about the bond to the old glue. It cost about $35 a day for the rental, plus I had to buy the grinding stones,but it was worth it.

[John Bridge]

Mornin' Gents,

What I said on the old forum and what I've said a lot of places is that we have had success going right over the asphalt emulsion, aka "blackjack" -- "cut back." Use a thin set like Versa Bond or Full Flex.

Sprinkling a little dry portland on the floor and sweeping it in keeps your feet from sticking to the emulsion. Just make sure there are no loose spots.

I've been doing it here in Houston for about 18 years and have had no problems I am aware of.

Glad you made it, Rob. I might need to make a change to the format of the forum form. Others have had problems seeing the "new thread" link. Maybe it ought to read "post new message" or something like that. I'm still learning how to manipulate the thing, and it seems I'm a slow learner.

[Rob Z]

Hello John and Bri

Thanks for the info. I have had some discussions with my contact people at Schluter, Laticrete, and Summitville on this topic.

The floor grinder and sand seems to be a cost effective, easy solution to prep the surface.

I'll let you all know how it turns out.

Rob