diagonal corner crack  Cracks 3_0

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Diagonal cracking is an inclined crack beginning at the tension surface of a concrete member. Steep diagonal cracks appear in concrete foundation due to point loads that exceed the compressive strength of the concrete. This type of failure, known as settlement, can happen due to “volume changes in clay soils due to fluctuation in their water content, increased pressure on a portion of the foundation, or long term consolidation of compressible clay under the foundation” [a]. If the soil under the footing cannot stand the compression force from the weight of the foundation and house/building, then the structure will sink and any adjacent walls that are adequately supported will resist this movement.

In addition to diagonal cracking caused by external effects, it can also occur from internal problems. Diagonal shrinkage cracks can occur in a concrete wall due to “improper mix or improper curing at the time the concrete was set in place” [b]. It is important to make sure that there is adequate soil to place the foundation/structure, and that the mix and curing of concrete was done properly.