If you find dried latex paint on a concrete surface, don't think it has to be a permanent stain. Although latex paint is easier to remove while it's wet, it can still be removed even if it has already dried. Whether you spilled some paint on your concrete driveway, or got paint splatters on your concrete floor while painting the walls, use the right products and methods to remove it safely and effectively.
Sweep the area with a broom to get rid of any loose dirt and debris. Take a putty knife and scrape off as much of the paint as possible. Apply some force when using the putty knife to effectively lift the paint from the surface.
Saturate a rag with household ammonia. Lay the rag on top of the latex paint spot.
Let the ammonia-soaked rag sit on the spot for 20 minutes. Take off the rag and scrub the spot with warm, soapy water and an abrasive sponge. Soak up the excess moisture with paper towels.
Saturate a rag with rubbing or denatured alcohol if the paint is still there. Lay the rag on the spot and leave it there for 20 minutes. Remove the rag, scrap the spot with a putty knife, then use the sponge and soapy water to scrub away any remaining paint. Soak up the moisture with paper towels.
Use a stronger solvent for stubborn paint that just won't budge. Apply a rag soaked with acetone or a commercial paint stripper to the spot for about 20 minutes. Take the rag off, scrape and scrub the area with warm, soapy water. Make sure to thoroughly clean the concrete with clean, soapy water once the paint is gone to remove any residue from the solvent.