How to Resurface or Overlay Concrete
If the concrete surface of your sidewalk or driveway starts to chip, flake, crumble or disintegrate, the main reason is that the concrete was not mixed or applied properly. To resurface or overlay is to put new concrete over the broken surface.
The difficulty is moderate. It can be done by anyone as long as instructions are followed.
The things that you will need are:
Concrete Resurfacer (for overlays up to 1/2 inch)
Portland cement, gravel, sand (for overlays more than 1/2 inch)
Pressure washer (optional)
Broom or brush
Squeegee with long handle
Wood strips (if needed)
Stakes (if needed)
In Figure 1, spalling has occured in the middle slab
Spalling is the term used to describe the chipping or flaking of concrete or other materials like masonry or stone. A possible cause for concrete spalling is that too much water was applied to the surface that was put into the form. The excess water diluted the cement which glues the sand and small stones together.
The surface of the damaged concrete must be prepared to take the new concrete. Loose concrete and dirt must be brushed and hosed down. Using a pressure washer will work better as it will remove loose pieces and clean at the same time.
For overlays up to ½ inch thick, the easiest material would be a concrete resurfacer such as the Quickrete concrete resurfacer product. The cracks and pits must be filled in with the Quickrete product and let dry.
After the cracks and pits have been repaired the concrete resurface can be applied. There are detailed instructions on the Quickrete product. The surface just need to be damped with water. Mix 1 part water for 7 parts resurfacer mix. (Example, one cup water for 7 cups mix). The mix is mixed with a power drill and paddle bit. The concrete is poured over the broken surface with a squeegee or trowel.
For resurfacing a concrete layer thicker than 1/2 inch, it will be better to use a Portland cement mix. The surface must be cleaned and washed as in Step 2. A mix of Portland cement and water to the consistency of paint should be brushed over the old surface first.
Create a form to allow the concrete to be shaped to the concrete slab you are going to repair. See Fig. 2. In this example, we have a walkway in the front yard. Strips of wood are used and staked to the ground. If there is no place to stake the strips of wood, creative ways to secure the form will have to be used. One example is to use chalk to hold the wood on a surface like concrete. The chalk can be peeled off later.
The wood strips can be made from long pieces of scrap wood or cut from plywood to suit the size of the form.
Use 3 parts gravel, 2 parts sand, and 2 parts Portland cement. The gravel must be about 1/3 the thickness of the layer you want over the old surface. Add water to the consistency of peanut butter.
Pour the Portland mixture into the form and wipe excess with a piece of 2 x 4. Before the cement gets hard, use a broom or brush to give the Portland mixture a rough finish.
After the concrete has hardened, spray a curing compound to make sure the water is retained and that the concrete dries properly. The curing compound can be found in most home improvement stores.