The most common way to remove paint from concrete is to apply a chemical paint stripper and scrub the paint from the surface. The process is easier if the concrete was sealed before the paint got onto the surface. If not, some of the color may cause permanent stains.
Concrete is porous and absorbs liquids, making this process time-consuming and labor-intensive. To begin, thoroughly clean the area that needs paint removed by sweeping the surface with a broom. Use a long-handled brush to apply a soap and water mixture to the surface, and then rinse thoroughly. Use a pressure washer to rinse the surface; if the paint was applied after a sealant, use a paint removing tip on the pressure washer wand to blast paint from the surface.
In some cases, you can use the pressure washer or a putty knife to scrape off and completely remove the paint. You could also use a power sander or rubbing stones to strip the paint from the surface of the concrete.
If these options do not work, apply a paint thinner chemical to the surface after thoroughly cleaning it. Use a stripping compound designed for the type of paint that needs to be removed, and wear gloves and a protective mask during the application. Allow the paint thinner to set for six to eight hours. Use a wire brush, a paint scraper or a pressure washer to remove the paint thinner. You may need additional applications to remove the paint stain completely.