Concrete can crack from a number of different causes. Inside concrete is subject to wear from daily use, and outside concrete is subject to wear from daily use, as well as the constant effects of weather. Newer concrete is less likely to need to be replaced, but cracks that are not repaired in a timely manner are likely to become bigger, and may even damage the concrete’s structural integrity. Patching even small cracks can strengthen concrete, as well as give it a longer lifespan.
This guide is intended for hairline cracks. For larger cracks, you will need to use a concrete patch. These can be bought at hardware stores and come with instructions that depend on the product you buy. Even after repairing a crack in concrete, it may still be structurally weakened. This means cracks may form more easily in the future. For concrete that has a large number of cracks, or is structurally weak, it may be best to replace the damaged area.
Mix portland cement and water to make a grout to repair the crack. Add enough water so that the mixture becomes a thick paste.