Things You'll Need
Mastic glue is commonly used to adhere tile, carpet and other flooring types to cement floors because it is strong, durable and long-lasting. These qualities make it almost impossible to remove the glue using conventional commercial cleaners. Before you can remove hardened mastic glue, you have to soften it using soy- or citrus-based adhesive removers, which are available at hardware stores, home improvement stores and most big box department stores. Both removers work equally well, but citrus-based adhesive removers typically take longer to soften the glue.
Open up all of the windows in the room. Most adhesive removers require you to work in well-ventilated areas. Put on safety goggles and gloves before you start working.
Use a putty knife, paint scraper or razor blade to scrape up as much of the glue as you can. Sweep up the glue scrapings and discard them.
Pour a soy- or citrus-based adhesive remover directly onto the residual glue. Allow the adhesive remover to work for about 30 minutes. Waiting times may vary from product to product, so check the instructions on the packaging for specific information.
Wipe up the glue with a damp cloth. Although the adhesive remover does soften the glue, you may need to scrub quite hard to get the glue off of the floor. If some of the glue will not come up with the rag, use your scraping tool to get the rest of it.
Mop the floor with hot water to rinse off the adhesive remover and bits of glue. Allow the floor to dry completely. If any glue remains, spot treat it with the adhesive remover and rinse the area again.