Cracks are formed mainly due to inadequate compression of the underlying ground before the concrete is poured, or improper construction at the expansion joints. The only solution available to this problem is crack repair.
Ensure the surface is thoroughly dry before beginning work. Chisel out the crack using a chisel and hammer. Vacuum the surface to get rid of debris and dust. Mix the patching compound as per the directions given by the manufacturers. Add a latex additive to it in order to improve its strength and flexibility for natural expansion. Apply the compound over the crack with the help of a small putty knife and smoothen up the surface. Allow surface to cure before filling it with an additional patch.
Prepare the surface for repair by keying, and cleaning the area. Mix the patching mortar according to instructions written in the manual. Using a putty knife, ensure the cracks are sealed with the mortar mix. Smoothen up the rough edges with a wooden float and use a metal trowel to give it a better finish. Apply water on the patched area, once a day, to improve bonding of the concrete.
The moment you discover the crack you must take prompt action to fix it. If you neglect it for long, it will develop into a much deeper crack and you may find it difficult to manage the repair work. On an average, concrete repair cost may vary in between $400 and $800 if you are hiring a professional.