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Various indicators help determine the severity of concrete cracks. The concrete cracks are assumed to be serious if they are active and widening continuously, allow moisture penetration, retain dirt, or are located in a high-visibility area. The structural cracks can influence both strength and durability of structural concrete.
The severity of the cracks can vary from one structure to another. Besides, the perspective of a person overseeing the work is equally important. For instance, a specific crack width may be acceptable by a contractor or engineer, but it may be unacceptable to the building occupants.
So, there is no clear line to determine the seriousness of concrete crack, and it should be ascertained based on the specifications and requirements of the project under consideration.
How to Determine the Severity of Concrete Cracks?
- Generally, cracks with a width of less than 0.3 mm are acceptable and do not affect the structure. However, they may develop and grow to become structural cracks. Therefore, one should monitor small cracks on houses or structures.
- Crack width greater than 0.3 mm can create problems for the durability of the structure.
- If the crack is static, then it is not severe. However, as the concrete crack widens gradually, it would ultimately become a structural crack and cause structural problems, unless the crack is repaired.
- When cracks on a horizontal concrete surface such as a concrete slab get widened to a degree of causing a tripping hazard, it is considered a severe crack and needs immediate repair.
- If a crack catches dirt and causes sanitation or maintenance problems, it is considered a severe crack.
- Cracks on slabs and foundation walls that permit the moisture seepage are severe and need suitable treatment.
- The maximum allowable crack width on the foundation is nearly 3.2 mm. Damping and watertight agents can bridge a crack width of 3.2 mm.
- It would be best to repair cracks that are located in high-visibility areas of a concrete structure.
- Short and, sometimes, vertical hairline cracks on the foundation wall would not cause structural problems.
- Long diagonal cracks on basement walls are a sign of overstressing of the basement wall. Frequently, cracks caused by overstressing originate from the upper corner of the foundation wall.
- Mostly, foundation settlement is the cause of the long diagonal cracks on the basement walls. So, it requires immediate action to tackle the problem. One may notice signs of foundation settlement in the superstructure in the form of jamming doors and windows.
- Cracks that appear within six hours of concrete placement are either plastic shrinkage cracks or plastic settlement cracks. The width of plastic and shrinkage cracks ranges from 1 mm to 2 mm; cracks with greater widths shall be repaired on priority. Segregation and bleeding of concrete are the causes of such types of cracks.
Structural cracks result from incorrect design, faulty construction, or overloading, which may endanger a building's safety and its occupants. Please read more here.
Non-structural cracks occur mostly due to internally induced stresses in building materials. These cracks normally do not endanger the safety but may look unsightly, creating an impression of faulty work, or give a feeling of instability. Please read more here.
The maximum allowable crack width on a foundation is nearly 3.2 mm. Damping and watertight agents can bridge a crack width of 3.2 mm.
Active cracks in concrete are live cracks which expand in length, width, and depth over time. These cracks are formed due to overloading and thermal expansion e.g. cracks due to freeze-thaw.
Various indicators help determine the severity of concrete cracks. The concrete cracks are assumed to be serious if they are active and continuously widening, allow moisture penetration, retain dirt, or are located in a high visibility area. The structural cracks can influence both strength and durability of structural concrete
Sketches/Maps of Concrete Cracks Observed in Visual Inspections
Evaluation of Cracks in Concrete to find Location and Extent of Cracking