Shot blasters though costly can be used to remove paint stains from concrete.
How to remove paint off concrete patio.
Remove old paint from a smaller patio 10 x 10 or so by mixing 1 cup of dishwasher soap and 2 quarts of hot water.
It has a vacuum attachment which then cleans up the released beads dusts and debris by suction.
This scrub action should remove most of the paint as well.
Break up the paint with the wire brush and scrape it away with the scraper.
Apply paint stripper in a thick even layer on the concrete until the stripper is twice as thick as the paint on the concrete.
You could also use a pressure washer for outdoor concrete surfaces such as driveways or patios.
It may require a couple of applications to achieve your goal.
Use a paintbrush or a paint sprayer to apply the paint stripper.
I would recommend using a pressure washer for your final rinse this ensures that the entire chemical is removed.
Apply the acid directly from the bottle with a sponge or cloth.
Once most of the paint comes off the concrete wash it thoroughly with a hose to remove any stubborn residue.
Use a wire scrub brush or a scraper to remove the loosened paint.
When you set out to remove paint from concrete the first thing to do is clean the surface of the concrete thoroughly.
Allow it to remain on the paint long enough to dissolve the paint.
Sweep the area to clean away dirt and debris.
Use the edge of a scraper to remove as much of the paint as possible.
Pour the solution on a small section of painted concrete and allow it to stand for 10 to 15 minutes.
After the stripper is set use the scrub brush to scrub it off.
How long can vary depending on how old and hard the paint is.
Clean the concrete surface thoroughly and let dry.
In most instances the stripper should be applied to the surface and left undisturbed for a specific amount of time.
To get oil out of concrete or remove unsightly paint or other stains fill both buckets with hot or warm water and add several squirts of dish soap to one of the buckets.
The abrasive material forced out under high pressure on the affected spot of concrete surface helps in paint removal.