By James Dulley
Dear James: The surface of our concrete sidewalk from the driveway is in bad condition, but the base seems sound. Can I just resurface it without replacing the entire sidewalk? — Sean R.
Dear Sean: It will take some hard work, but you should be able to repair the sidewalk. If you are diligent and take your time, it should look better than when it was new.
In most cases, the cause of a crumbling concrete surface is poor workmanship when it was initially poured. They probably added excess water when smoothing the surface, which weakens the concrete.
Adding a one- to two-inch thick layer of concrete over the existing walkway is the best method to repair it. Don’t attempt to do the entire job at one time. Break it down into several weekend projects doing just one or two control joint sections a time. Cleaning off the crumbling spots is as much work as repairing them.
There are four simple steps to making the repair. The basic concrete overlay procedure requires four simple steps – 1) clean out the bad areas, 2) paint a thin cement glue layer, 3) apply the overlay, and 4) level the overlay. It is kind of like decorating a cake with icing.
First use a broom to remove the larger loose pieces. Use a large masonry chisel and hammer to chip out all the crumbling concrete around these areas and to examine other suspect spots. When you are done, spray it off with a high-pressure hose nozzle.
Place wood concrete forms along the sides of the sidewalk. To get the height even, make spacer blocks and place a straight 2×4 across them. This determines the height of the forms. Where it must blend to your front step or driveway, taper the overlay thickness down.
Wet down the area to be repaired and cover it with plastic for several hours. It is important for the existing concrete to be saturated with water so that it does not draw the moisture rapidly out of the glue and overlay.
Here is the fun part: mixing and applying the cement glue and the concrete overlay. The cement glue is easy to mix – about equal parts of fine sand and cement. Add enough water so that it is the consistency of thick paint.
The actual concrete overlay should be like thick cream of wheat. A mixture of about three parts of sand to one part of cement usually works well. If you add small gravel for a different appearance, the largest pieces should be not more than 30 percent of the thickness of the overlay. Larger gravel will reduce the chances of success and may not look good.
You will need a helper at this point. Have your helper paint a thin layer of the cement glue first. Within five minutes, spread the overlay concrete layer in the forms. Use the long 2×4 again to level off the overlay. Lay it on top of the forms and move it in a back-and-forth sawing motion over the concrete.
Let it set up for 15 to 30 minutes. When it is fairly solid, finish the top surface. If you are inexperienced at this, use a swirling broom finishing method. It makes an attractive surface high-traction surface and is easier than floating it smoother.
Send your questions to Here’s How, 6906 Royalgreen Dr., Cincinnati, OH 45244 or visit www.dulley.com.