When installed properly, concrete is one of the most durable building materials that provides strength, rigidity and resilience to the structure.
However, these characteristics also account for the lack of flexibility of concrete structures to move in response to environmental and volume changes which results in cracks.
This article presents a brief account of the various causes of concrete cracks and provides means for their control.
Poor Workmanship
Concrete cracks are mostly the result of workers’ error who add surplus water during construction to improve the workability of concrete and to provide an attractive finish to the structure.
However, evaporation of the excess mixing water causes concrete slabs to shrink, which reduces the strength of the structure, causing cracks in the future.
Moreover, excessive water, combined with a higher cement content also increase the temperature difference between the interior and the exterior portions of the structure. This results in increased thermal stress, causing the concrete to crack.
Therefore, it is always recommended to seek the professional assistance of experienced concrete contractors. They guarantee the strength and durability of the structure by making sure that water to cement ration is at its optimum level.
Excessive exposure to moisture, weather and foot traffic are some common causes of cracks in concrete.
Concrete Shrinkage
Concrete shrinkage cracking often occurs throughout the lifecycle of concrete structures, and is primarily classified into two categories- plastic (before hardening) and drying (after hardening) cracking.
Plastic shrinkage cracks are caused by the rapid evaporation of water from concrete surface due to a combination of factors which include air and concrete temperature, relative humidity and wind velocity at the surface of the concrete.
On the other hand, drying shrinkage cracks occur due to the loss of moisture from the cement paste constituent.
The U.S. Bureau of Reclamation relates high water content as the primary cause of drying shrinkage.
Although shrinkage concrete cracks do not cause much structural damage to the building, they need to be sealed against water entry by using masonry patching compound on the surface.
Settlement Cracks
Also known as structural cracks, settlement cracks in concrete are formed during the initial setting of concrete. Considering the tendency of concrete to consolidate, it is often restrained by reinforcing steel which results in voids or cracks adjacent to the restraining element.
Since settlement cracks are typically continuous, and spread from one side to the other, they are capable of causing serious structural damage.
Settlement cracks can be appropriately treated by injecting structural epoxy.
The epoxy acts as a liquid shim which binds the internal movement of the crack, thus, preventing the crack from closing due to any additional movement. Many contractors also install an anti-fracture membrane over the repair area to prevent reflective energy transfer.