How do I repair the vertical cracks of a compound wall?

PROCEDURE FOR REPAIR OF CRACKS:

For small cracks (3 mm or less):

• Use screwdriver to chip away any flakes or loose concrete.
• Scour the crack with a wire brush to remove any dirt and debris.
• Rinse the cracked area using the garden hose.
• Mix up a small batch of concrete patching compound, available at most hardware stores. Adding a latex additive will for the natural expansion of concrete through cold and hot weather.
• Trowel the compound into the crack using a small putty knife.
• Smooth the surface while the compound is still moist; concrete compounds begin to set up very quickly.
• Allow the crack repair to dry thoroughly before walking or driving on the surface.

For large concrete cracks (6 mm or more):

While the beginning steps are the same for repairing large cracks as for small cracks, larger cracks in concrete require the use of more advanced techniques – caulking or sand packing.

• Use a screwdriver to chip away any flakes or loose concrete.
• Scour the crack with a wire brush to remove any dirt and debris.
• Rinse the cracked area using the garden hose.
• If you choose to employ the caulking method, siliconized latex (or polyurethane) concrete caulk is needed. Using caulking gun, force the caulk deep into the crack along the length and breadth of the crack. The caulk will expand to fill the crack, and the nature of the substance will allow for expansion and contraction during weather extremes, cutting down on the frequency of the future repairs. The caulking compound will self-level so there is no need to smooth the surface, but for large cracks, multiple applications may be needed.
• If you choose to use the sand packing method, you will need some sand and concrete patching compound, preferably with a latex additive for flexibility. Pour in a layer of sand to help fill the crack, and then apply the patching compound with trowel. Smooth the surface quickly, and feather the new surface into the existing edges for a finished look.