If you would like to introduce some color, achieve water protection or restore the look of your concrete patio, sidewalk, pool deck, or any other outdoor horizontal masonry surface, you can paint it. We have talked about painting exterior concrete surfaces before. However, painting horizontal surfaces is different from vertical ones, like foundation walls, because patios, sidewalks, etc. are affected by standing water and traffic. Therefore, today we will address the specifics of horizontal outdoor concrete surfaces.
New concrete should be left along for at least 28-30 days, and it does not require such an extensive and thorough preparation as the older surfaces. If it is very smooth, etching is still required though. See below for etching process.
Old concrete has accumulated dirt, algae, etc. So, before painting old patios or sidewalks, power wash thoroughly. Most surely, it has various size cracks. Fill larger than a hair width cracks with a flexible concrete caulk (filler), like Sherwin-Williams Stampede caulk or any other elastomeric caulk. However, perform the etching procedure fist, before patching.
Concrete is etched with an acid, like a muriatic or Phosphoric acid, the solution of which is scrubbed into the surface with a very stiff brush. Refer to the acid’s container for instructions. Always add acid to water. Never add water to acid while in the process of diluting the etching solution. Protect all surfaces not being etched from accidental splashes or spills by masking off these areas. The above acids are very harmful, so wear rubber boots, long pants, long-sleeved clothing, rubber gloves, eye protection, and breathing protection. Wash the surface thoroughly with water to remove the acid and then squeegee dry.
Dry patio, pool deck or sidewalk surfaces thoroughly before applying a coating. Trapped water can cause bulging.
Concrete stains are the best choice for the outdoor surfaces like patios, sidewalks, and pool decks. They are more elastic to expand and contract with concrete and to fill tiny cracks and gaps. A good water based product for pool deck should also work. Epoxies are also used, but they may get discolored outdoors. You may use Sherwin-Williams H&C Concrete Stain, SherCrete Flexible concrete waterproofer (better elasticity), Seal-Krete Concrete Colors, Behr Porch and Patio Floor, and others.
Let the coating dry for at least 24 hours before walking on it (each product has its own requirements).
Note: additives like play box sand or shark bite grit may be added if you wish to ensure good slip resistance because they will introduce texture to the coating.