Why Does Concrete Crack?

Shrinkage, the most common cause of cracks in concrete is the shrinkage that occurs as the material dries.

Temperature Changes

Lack of Support

Rusting

Spalling, typically occurs when too much water is added to the concrete mixture

Shrinkage

• The most common cause of cracks in concrete is the shrinkage that occurs as the material dries. As concrete cures, the water that has been mixed with the cement and sand begins to evaporate. This causes the concrete to shrink slightly. Because the concrete surface is restrained by form work or surrounding objects

• Temperature change is a major cause of cracks in large concrete applications. This is because of the temperature variations between concrete that is poured first and subsequent layers of concrete. These temperature variations can cause some portions of the slab to expand while others are shrinking, which leads to cracks.

• Some of the most severe cracks in concrete are caused by inadequate structural support, which occurs when the soil beneath a concrete slab shifts position or is eroded by wind and rain. It can also be caused by poor installation, including improper use of rebar or insufficient form work.

  Rusting

  • Many items made from concrete contain metal reinforcement, which help increase the material's tensile strength. These reinforcements include wire mesh, rebar or steel beams. If these materials start to rust, the rust will cause the concrete to expand. This expansion can cause hairline cracks and small surface cracks.

    Spalling

    • Spalling is the term given to concrete that has a rough, flaky surface. This condition is the result of hundreds of tiny cracks, which usually appear only on the surface of the concrete. Spalling typically occurs when too much water is added to the concrete mixture, or when the surface layer dries faster than interior layers.

     

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