Q: We are removing an old parquet floor. What is the best way to remove the glue left behind on the concrete slab?
A: I’m not sure what kind of adhesive you are dealing with. If it typical white or pink parquet adhesive, it is water soluble. I’m not suggesting you flood the floor, but you might wet a small area with warm water and see if it loosens the adhesive.
If it doesn’t scrape off you might have to rent a type of polisher which has 3 heads and can have special attachments for scarifying the concrete. Those would be your main choices. Floor scraper or machine for removing adhesive from a rental. Or hire someone who has the equipment.