Removing old dried on paint from concrete can be tedious work. Dried on paint on a prosperous surface such as concrete can be removed using a few different methods, but you should try the easiest method first and if that doesn't work, you can try the other methods. Sometimes a combination of methods works very well to remove the dried-on paint. However, you must be careful when using the tools and chemicals.
Wear goggles and gloves when trying to remove dried-on paint from concrete.
Use a putty knife to remove as much of the dried paint as possible. Sometimes angling the putty knife so the blade gets under the paint spot will help loosen the paint and chip it off the concrete.
Pour a commercial paint remover on the paint stain. Let the solution sit on the paint stain for about 30 minutes to soften the paint and lift it up off the concrete. The area you are working in with paint remover should be well ventilated.
Use the hard bristle scrub brush in a circular motion to remove the softened paint. After you have removed the paint or most of the paint, use clean water and the scrub brush to wash the area. Wipe up the water and loosen paint with a rag. If there is any paint left, you can use an abrasive cleaner such as Ajax or Comet with water and scrub brush to remove the paint that remains.
Apply water pressure to stubborn dried-on paint using a pressure washer. If the pressure washer is used in a basement, you will need to have a drain for the water to run down while you are using the unit. After applying water pressure on the spot, use a putty knife to pry up any remaining paint.
An alternative to removing paint that is embedded in the grain of the concrete is to acid clean the concrete surface, but this method will remove the top layer of the concrete. This should be the last resort only.