Sometimes you need two-part epoxies for added bonding. If the repairs you' re dealing with are fairly small in scale, you'll probably need only a bag or two of sand mix, such as Quikrete or Sakrete. This helps give you more surface for the patching material to bond to, Barrett said. Cutting a V also helps get rid of contaminants. KTA-Tator Inc. This doesn't just apply to floors.
Airborne contaminants can reach inside cracks on walls, too.
Regardless of the type of patching material you'll be using, some basic mechanical repair work must be performed on cracks before it can be applied. For small cracks, you need a notch about one inch deep and two to three inches wide, which you can make with a maul and chisel. Use a wire brush and scrape the area to remove any loose concrete, then blow out and rinse the area thoroughly to remove any loose stones. Make sure you sift the mix to a very fine consistency before using it, however. The resulting mixture should look like the flour and water mixture you use to make gravy.