Dave Ashberry of King Packaged Materials joins Jon in running down the various methods and products used making surface repairs to concrete.
Cracked corners or edges on concrete steps are a major hazard and should be fixed. Top & Bond is one of the basic surface patching materials available. Its holding power is increased if you use a bonding agent first. Note, you must apply the patch while the bonding agent is still tacky, not after it has hardened. Do not use a bonding agent if you are using a patching material that is "polymer modified", they may not be compatible.
Swift Set, shown in the photo, is a similar material designed for vertical applications where the slow setting time of Top & Bond would present a sagging problem. Rather than building forms, you just hold one trowel in place for a few minutes.
Patching materials are available at all renovation centres. Read the packages carefully to choose the one you need. Done properly with good materials, the patch can last quite a while.