After the coating has fully cured, a waterproofing membrane should be applied to prevent further spalling. Patching can be a repair option for random or localised damage. If your concrete has already succumbed to spalling, don't worry, it can be repaired. The type of repair and the work involved depends on where the concrete spalling is located, how deep it is, whether it is on a vertical or horizontal surface and whether there is any exposed rebar.
You can repair and coat your spalled concrete in a number of ways. You can buy products that apply a very thin layer to the concrete. Large ready-mixed concrete bag manufacturers make them, as do other specialised companies. These products work, but be aware of their limitations.
A very important step, taught to me by a wise old concrete mason decades ago, is to apply a very thin coat of cement paint to the old concrete before applying stucco. Polymer modified cement patches are a good choice for areas with very deep pitting, broken concrete lips and edges, deep holes and other areas where the repair may need to be shaped, such as the edge of a concrete apron. Remember - If you are going to follow with an epoxy coating or paint, these repaired areas will still need to be prepared by grinding just like the rest of the existing concrete. The concrete rejuvenation product is sealed to ensure no recurrence of spalling.
Concrete resurfacing is used to repair and revitalise concrete surfaces that suffer from things as minor as staining and light corrosion due to the elements, to more structural problems such as spalling. Once all repairs have been made, be sure to protect the garage floor from further pitting or spalling by sealing the floor or applying a coating. The most effective way to prevent concrete spalling is to use a waterproof sealant to prevent water from entering where it can cause damage. Spalling is often caused by cold winter weather that subjects concrete to freeze-thaw cycles.
If you have spalling on a basement wall or other vertical concrete surface, the solution can be a little tricky. What happens is that water settles on the garage floor and works its way into the capillaries of the concrete. Corroded steel can expand up to ten times its original volume, putting stress on the surrounding concrete. Repairing a pitted or spalled garage floor is only intimidating because most people don't know what to use or how to get started.
To fix a spalling concrete wall, first cut away the concrete around the spalled area. In order for the stucco to permanently adhere to the spalled concrete, the old concrete must be clean and sound, with all loose concrete removed. Concrete spalling is the result of a chemical and physical process that occurs within the concrete itself.