I forgot to answer your other two questions. The expansion joint between the slab and block stem wall can be filled with a self-leveling polyurethane filler such as SikaFlex SL after a coating is installed. This article here explains more about the different types of joints and what materials you can use to fill them with. For the block stem wall, we recommend color matching your coating with a standard concrete paint and then painting it as is. Stem walls are extremely porous and absorb a lot of material. It can get expensive buying the extra material that you would need to coat it. If you do want to coat it, the only prep work that is typically required is to clean it well. Do not apply the coating thick or it will slump and run before it can begin to cure. It may require two coats.

Hi Tyler. If you have any significant oil spills or dirty concrete it’s important to degrease and clean the surface first. After grinding, make sure to check any oil spots with a water drop test to verify that it will absorb it and not repel it. If it does not absorb the water, then more degreasing of the spot will be required.

Hi Frustrated 🙂 The white residue on the surface is not acid. It’s left over mineral deposits and insoluble calcium phosphate. It does need to be mostly removed before applying a coating or it will hinder proper adhesion. A light grinding will most certainly remove it, however, it’s still very important to neutralize the concrete as best you can first. If you don’t do this, the acid solution will remain active down in the concrete. In some cases, it can cause rebar to rust and expand (thus causing cracks) as well as wreak havoc on coating adhesion. Before you grind, soak the concrete with a solution of 1 cup of baking soda to 1 gallon of water. Let it sit for a few minutes to absorb into the concrete and then rinse off with a hose and nozzle. Pressure washing is not needed. Once it dries, you can grind.

Your articles are amazing wish I read them before I started the prep. I did an acid etch and didn’t know that I have to neutralize it. I did pressure washing 4 times but the concrete is still white and powdery. I don’t have the patience to etch again and keep washing until I hate my life for starting this project. At this point can just grind and be done with it? Will remove the acid on top? Or do I have to still neutralize it and then grid? And I’m also mad that the products don’t come with proper instructions

Hi Hannah. This is usually the result of letting the floor start to dry out before rinsing or not rinsing well enough. As you have found out, it can be a real bear to scrub off. We have found that mixing a solution of 1/2 cup TSP to 1 gallon of warm water helps to lift it. Pour some on an approximate 5’x5′ section, scrub with a stiff bristled deck brush, and then rinse with the pressure washer. Start from the back and work forward. This should do the trick. Don’t worry if it doesn’t come perfectly clean. As long as you get the majority of it, you should be fine.