Concrete cracks: Causes, Evaluation, and Repairs
While some cracks can occur in concrete structures during the pre-hardening stage, others happen in the post-hardening stage over time despite the care and preventive measures taken. When the concrete becomes older, the cracks become sources of leakage and give access to moisture, carbon dioxide, chloride, and other aggressive gases, chemicals, or substances into the concrete, leading to degradation of the structure.
Should all kinds of cracks concern you?
Yes. But, structural cracks require immediate repairs, and non-structural cracks’ repairs can be delayed. However, all kinds of concrete cracks should be fixed sooner or later.
Structural cracks formed due to faulty construction, incorrect design, or overloading can jeopardize the durability and safety of the structure.
Non-structural cracks formed because of internally induced stresses in building materials may not weaken the structure. However, if such cracks are left untreated, they may expose the concrete to moisture and other destructive environmental substances, leading to corrosion of reinforcement and making the concrete structure unsafe.
Also, the cracks can be classified as dormant and active cracks, depending on their length, depth, and width. While dormant cracks can be easily repaired, active cracks are difficult to repair. Besides, active cracks are required to be observed for at least six months by a structural engineering Dallas expert before any repairs are carried out.
Causes of concrete cracks
During pre-hardening stage
During this stage, the cracks are mainly due to drying shrinkage and plastic shrinkage that occur in the process of concrete settling.
The factors contributing to the formation of drying shrinkage cracks are:
- Wind and higher temperature during concrete casting.
- Leading to rapid drying of concrete.
- The difference in ambient temperature.
- Relative humidity.
The factors contributing to the formation of plastic shrinkage cracks are:
- Absence of moist curing post setting of concrete in the green stage.
- Higher water/cement ratio.
- Excessive water absorption by aggregates from the concrete mix.
During this stage, the construction defect-related cracks are due to gaps in formworks, absence of required cover, segregation of mix, excessive vibration, lack of joints, cold joints, ineffective joint treatment for expansion and contraction joints, and absence of curing for a specified period.
During post-hardening stage
The cracks caused during this period are mainly due to poor quality of materials, thermal shrinkage cracks, long-term drying shrinkage cracks, and chemical and electrochemical corrosion.
Evaluation and Repairs
Before repairing the cracks, it is essential to detect the exact nature of the cracks and the causes. Careful visual observation can tell you about the cause of the crack. The location and pattern (diagonal, transverse, longitudinal, vertical, horizontal) of the crack can tell you about its nature. Some non-destructive tests like the ultrasonic pulse velocity and tools like digital crack measuring gauge can be used to measure the depth and width of the crack.
It requires proper training to identify and diagnose the concrete cracks properly. If you lack expertise and formal training, you may falter.
Therefore, if you notice any cracks, immediately consult experienced and competent structural engineering Dallas professionals to classify the severity of cracks in concrete structures, thoroughly investigate the cause behind the cracks, and figure out the most effective repair method if required.
Minimizing cracks in concrete
While cracks in concrete structures can be repaired, it is better to prevent or at least minimize them through clever design and proper, accurate construction.
At Falkofske Engineering, we believe in paying attention to intricate details, project-specific concrete specifications, and quality control and supervision during construction, all of which contribute to durable concrete structures with excellent design.