Thursday''s Ask the Experts question from a cleaning professional on the International Custodial Advisors Network (ICAN) "Ask the Experts" page: What is the best method to completely remove old multi-purpose floor covering adhesive from concrete? There was carpet glued to the floor, and when removed the glue remains. New tile is to be installed so the glue needs to be completely removed.
On concrete, there is less concern about scraping or scratching the floor than with tile or wood, so I would try one suggestion I’ve read about and that is to use a sturdy hand-held scraper after softening the adhesive with boiling water.
Pour the boiling water onto a small area, wait a few minutes for it to work, and then use the long handled scraper.
Other approaches would include the the use of a commerical adhesiver remover or a wire brush or scraper attachment for a standard rotary floor machine.
Keep in mind that there are numerous types of adhesive ...
— Lynn E. Krafft, ICAN/ATEX associate editor, firstname.lastname@example.org