try a product called GoldSolv sold at www.sspenviro.com It worked as advertised for me when we removed some old VCT before putting ceramic tile down over the concrete.

I recommend mechanical removal means.

When using chemicals, it may have adverse effects with any new coatings, surfaces, or adhesives being applied unless the product used is sufficiently neutralized.

We use the Pearle Abrasives HEXPIN Surface Preparation System to mechanically scrape vct "cutback".

As always, ensure it does not contain asbestos (if installed prior to 1979 - if installed after 1979 you should be safe unless someone broke the law).

A construction equipment rental facility may have it or something like it. If not, a mechanical grit or diamon grinder can also be used.

http://flooringworld.org/floorsearch.php?query=pearle+abrasives+hexpin+surface+preparation+system

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The right way and the wrong way.

Do it right everytime.

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