Flooring Tile - Thinset/ceramic over sealed mastic

I am getting rready to put ceramic tile in my laundry room. Just read on another post that there is nothing that needs to be done to the concrete floor to prepare it (other that a good cleaning). Unless of course it has been sealed. Well part of my floor had been covered in asbestos tile which has been removed. We had the remaining mastic sealed. Will the thinset work over this sealed mastic? If not is there some sort of glue that I can use just for this portion of the floor, about 40% of the total surface area. Thanks.

What do you mean by "the mastic was sealed". I understand the old VCT has a glue under it that remained after the tile were taken up but then what did you use to seal it and how much of the glue remained on the floor?

Sorry for not being clear. We had an abatement company come in and remove the tile. We chose to leave the mastic in place and the company put some sort of clear sealant over it. Not sure exactly what kind. It appears that a good deal of the mastic remains, although it is very smooth.

Paints and sealers are known *bondbreakers* when it comes to tile installations. The remedy here would be to shotblast or sandblast or mechanically remove the sealer and adhesive residue to again expose raw concrete.

It's not likely you are going to do this.

So..........your next best plan of attack would be to install your tile using a 'dryset' thinset mortar that you yourself mix with its compatible additive thereby creating your-own modified thinset that would have more tack and be stronger than the other (already) modified thinsets you would buy.:)

Thanks. I will try this for the sealed portion of the floor.

You could do the whole floor that way, not just the part over the adhesive.