This video shows you how to make an old concrete patio look like slate with a sprayed concrete overlay. It’s hosted by Tim, a professional contractor with Decorative Concrete in Virginia. The first thing you should do is remove any mold and grind off the old paint from the concrete if there is any.
For a smaller project, you can do this using a hand grinder and HEPA vacuum.
The next step is to acid etch the concrete, which opens the pores and allows the concrete overlay to stick to it. This can be done using phosphoric or muriatic acid. Tim prefers to use phosphoric acid, but whichever you can get your hands on should do the trick. Be sure to dilute the acid with water and apply it using a pump sprayer. Once the acid dries, rinse it off with a pressure washer.
You will then need to mix the overlay. Put water in a bucket and follow this up with a color pack, mixing everything together with a Collomix mixer. This coat will serve as the grout line color of the slate line pattern. Pour it on the ground, spread it with a magic trowel, and let it cure overnight. Apply the pattern and concrete overlay the next day. Now you know how to refurbish and renew your concrete patio!