The Reasons for Concrete Cracks

Temperature Changes

• Temperature changes are a major cause of cracks in larger concrete areas. This is because of temperature variations that occur between the concrete that is poured first, and the subsequent layers. When temperature variations take place, there are some portions of concrete that need to expand, while others need to shrink--which in turn leads to cracking. If the temperature variation is extreme, the cracks will be deeper and more pronounced.

Metal Rusting

• Some items made from concrete contain some sort of metal reinforcement that helps to increase the material's tensile strength. These metal reinforcements include reinforcing bars, steel beams or wire mesh. If these reinforcements begin to rust, the concrete will be forced to expand. With such an expansion come hairline cracks and small surface cracks in the concrete. The cracks then allow water into the concrete, which in turn causes the metal to rust more.

Lack of Support

• Structural support plays a very important role in concrete. If there is inadequate structural support--such as when the soil beneath a concrete slab shifts its position or is eroded by wind and rain--there is a possibility of severe cracks in the concrete.

Shrinking

• One of the most common causes of concrete cracks is shrinkage. Shrinkage occurs as the material starts to dry. While the concrete curs, the water that was mixed with the cement and sand begins to evaporate, which in turns causes the concrete to shrink slightly. This shrinking process leads to cracking.