wet scrape the adhesive with a 4-5 inch razor blade scraper. Mechanically remove any contamination in the substrate by an approved method. Mechanically cleaning removes the contaminates and the concrete to which it is adhered leaving only a clean, sound, and solid surface behind.
We recommend that all concrete substrate preparation proceed using one or more of the following mechanical methods: shotblasting, scarifying, grinding, sandblasting, scabbling ( bush hammering ) chiseling, and in some cases, high-pressure water blasting.
Methods to avoid: acid washing. The use of sanding equipment is not an effecive method to remove adhesives, curing and sealing compounds.
All types of solvents should be avoided Their use will drive oil, grease and other contaminates further into the concrete, only to permit their release back to the surface at a later time,
Never use adhesive removers or solvents to remove contaminates from porous concrete. These materials can carry contaminates into the pores of the concrete, which will later migrate back to the surface resulting in a floor covering, floor coating bond failure.
Concrete coating failures are expensive, and improper substrate preparation causes 90 % of all coatings and flooring installation failures.
Never had an installation bonding issue in 37 years using the above preparation methods.