Clean the slab and fill deep holes and cracks. Spread it out gently, then let it rest. When doing crack repairs in concrete, you should always use an epoxy, polyurethane or polyurea crack repair product that can be sanded. They will cure and harden to a greater force than concrete.
One of our favorites that we've looked at is Xtreme Set 100 by Legacy Industrial. This is a fast-setting 2-part polyurea. It requires you to fill the cracks with sand on the surface, and then pour the polyurea filler into the sand. A small area that is only 1″ deep doesn't need the 30 days.
The reason why concrete is being dusted is because too much water was used on the surface or even in the mixture. A common mistake people make is to add a little water when applying the palette to make it look smooth. This weakens the surface layer, and small fines in the concrete rise to the surface. This surface is a weak layer and will continue to dust and deteriorate until the coating no longer adheres to the joint.
For larger areas of pitting and chipping, we recommend using a 100% epoxy concrete patch with a sand aggregate. Silica sand is mixed with epoxy resin to act as a filler. Legacy Industrial's 5 ton epoxy patch kit is a good example of this. Epoxy is a common way to fill larger cracks, and so is a mixture of polymerized concrete.
The polymer acts as a binder and helps to adhere the filler to the rest of the original concrete on the floor. It is more common in areas where a parked car can deposit road salts and de-icing liquid on concrete. If moisture penetrates through the cracks and reaches the rebar, the rebar can rust and damage the concrete. The purpose of these joints is to weaken the concrete so that if the concrete cracks, often due to shrinkage, it will crack at the weakest point, which is often where the control joints were placed.
This also includes broken concrete edges and edges, deep holes, and areas where repair may need to be shaped. Once cured, you can grind or sand repairs flush with concrete to accept paint or an epoxy coating. For larger cracks where the repair will be only from the crack, then it is not necessary to clean the entire garage floor, only the crack itself. To reverse these imperfections before they cause deeper structural problems, you will need to smooth the surface with a premium product such as concrete leveler.
The two most common causes for weak concrete on garage floors are that there was not enough cement in the concrete mix, therefore cheaper, or that too much water was added to the concrete when it was poured from the truck to make it easier for the finishers to place it. Another key advantage of repairing cracks in a garage, is that in the process of assessing the type of crack and the cause, you can discover an unknown problem that you did not realize you had. One thing to keep in mind if you are planning to apply a clearcoat sealer to your concrete is that any tile you have made will be enhanced by the sealant. The good thing about polymer-modified cement products is that they are quite easy to work with and adhere much better than standard concrete mix.
Then mix enough concrete leveler with water to cover the entire surface of the garage floor while filling the depression. After carrying out all repairs, be sure to protect the garage floor from further pitting or splintering by sealing the floor or applying a coating. The reason for not using them is that they cannot be sanded, most do not accept paint and some shrink over time and separate from concrete. Trying to repair every little crack in a badly cracked and damaged garage floor is not practical, it would look terrible and just break again.