Coating your exposed aggregate concrete is a great way to seal it from the elements and increase its lifespan. The right tools and techniques can make the process as successful as possible. Here are five essential items you need if you want to make the most of your sealing job:
1. Pressure Washer
Use a pressure washer to clean your exposed aggregate before you begin adding coating or sealant. Pressure washing gets in between the bumps, valleys and ridges of your aggregate, ensuring dirt, debris, cobwebs or other elements don't prevent your coating from adhering well.
2. Water Dropper
Even though you have pressure washed the concrete, you need to make sure that it doesn't have any water-resistant chemicals coating it. If contaminants are lining its surface, it makes it impossible for the coating or sealing to properly adhere to the concrete. The easiest way to test that your exposed aggregate doesn't have any water-resistant chemicals coating it is with an absorption test.
Place a few drops of water on the surface and wait for it to be absorbed by the concrete. If the water is absorbed, your concrete is ready to be coated. However, if the water is not absorbed relatively quickly, your concrete may be coated with something. Use an alkaline concrete cleaner to clean your exposed aggregate -- this type of cleaner is the most effective at breaking down layers of grease and water-resistant chemicals. After cleaning, try the absorption test again. If the water still doesn't get absorbed, talk with a concrete contractor about possible advanced solutions.
3. pH Pencil
Look at the instructions on the coating you have purchased. Most coatings are designed to work with concrete or exposed aggregate at a certain pH level. If the pH is too high, the coating may not adhere well.
To make sure your concrete is at the right level, use a pH pencil to test it. You mark the pencil on the concrete, and then, you look at what colour appears. If the pH is too high and the concrete has been recently poured, just let the concrete set longer. It will become more neutral through the process.
4. Relative Humidity Probe
A new relative humidity test can measure the humidity levels of your concrete. To use these tests, you drill into the exposed aggregate, and you use a relative humidity probe to assess the moisture levels of your concrete.
Ideally, you want relative humidity levels to be less than 75 percent. Remember that when you add sealant, you lock in the moisture of the concrete and ultimately increase its humidity levels. For that reason, starting with as little humidity as possible is the most effective.