The Most Common Types of Cracks in Concrete and What They Mean
by TRP Ready Mix on April 11, 2020
Understanding the Various Types of Concrete Cracking
Whenever there is a change in temperature or moisture, concrete can expand and contract just as other construction materials do. Therefore, making provisions to allow for this expansion is necessary. But if space is insufficient, cracks can form as a result of lacking proper load and support conditions.
Cracks which appear in the early stages are typically not very critical. They do not affect structural integrity, strength or life of the structure. Cracks which appear in later stages are absolutely critical and may affect the integrity, strength or life of the structure.
Freezing and thawing cycles can have a significant impact and lead to deterioration of the concrete structure.
In the below article, we will explore the different types of cracks to look for.
The most Common Types of Concrete Cracks
Several different factors can cause concrete cracks; however, they are mostly caused by poor design and/or construction, such as:
- Inadequate or improper curing of concrete
- Improper finishing of concrete
- Excessive water in concrete
- Improper compaction of earth,
- Subgrade preparation and improper jointing practices
With that being said, let’s break down the most common types of cracks.
This type of cracking will most likely occur due to high evaporation rates, which cause the concrete surface to dry out before it has set. These cracks are unsightly but rarely impact the strength or durability of concrete floors and pavement.
Concrete can expand due to heat, which can lead to the concrete pushing against anything in its path. When neither surface has the ability to flex, the force can be enough to cause cracking. Joints made of material such as asphalt, rubber or lumber act as shock absorbers, which relieve the stress that the expansion can place on concrete.
Heaving is caused by frozen ground, which can result in concrete lifting by several inches before thawing and settling. The freezing and thawing cycle is a significant factor in contributing to cracking. The slab must be free to move with the ground, otherwise it will most definitely crack.
The main cause of hairline cracks in concrete are due to plastic shrinkage. This is caused by the rapid depletion of moisture from the fresh concrete within its plastic state. Variations in air temperature, concrete temperature, relative humidity and wind velocity at the surface can cause high rates of evaporation in either hot or cold weather.
Ground settling below a concrete slab can cause cracking. This occurs where a void is created in the ground below the concrete surface.
Structural cracks are caused by poor construction, swollen soil, poor soil bearing, or overloading. Structural cracks can usually be repaired by installing carbon fiber strips to damaged walls.
How to Repair Cracks in Concrete
The first step in concrete crack repair is to clear out chipped, loose, or unstable concrete from the area. This sometimes requires a hammer and chisel which allows you to break away the pieces. Cracks may need to be widened in some areas. Once the section has been prepared, sweep away all loose debris. A pressure washer or water hose should be used to clean the area, which will contribute to obtaining good contact between the concrete and repair material.
In some cases, a finishing trowel may be required. This can be used to apply pressure to fill some of the voids. It will also help to push material into the voids and smooth the surface of the repair area. The finishing trowel can help put a neat edge along the side of the repair. A brush can smooth and blend the patch material into the existing concrete surface.
The Importance of Reinforcing
While it is not possible to completely prevent cracks in concrete, they can be minimized by taking the proper precautions. Reinforcement is a crucial step to ensure that your structure remains intact, along with:
- Proper design for anticipated loads
- Providing proper contraction and isolation joints
- Sufficient sub grade which should be made for slab on grade
- Proper placement and finishing
- Sufficient time given for successful curing
A Common but Important Issue to Keep an Eye On
Cracks in concrete are very common and they develop when stresses in the concrete exceed its strength. Cracks are often caused by normal shrinkage of the concrete when hardening or drying. Cracks are best fixed at an early stage to help protect its longevity and integrity. The purpose of these repairs is to improve the durability and wear of a surface, reduce its permeability and to prevent the development of corrosion in the reinforcement steel. The ultimate goal is to ensure that the integrity of the concrete elements are not compromised. Your local professional can assist you with planning, development and ensuring that all of the necessary steps are taken.