It is not uncommon to observe cracks in concrete structures, but all breaks aren’t the same. Several factors contribute to cracking. Some may not be a structural concern, but some may require direct attention. It’s essential to address these concerns because the effects of cracks in concrete structures could cause long-term damage.
3 Reasons Cracks Occur and the Effects It Has on Concrete Structures
There are three main reasons you might observe cracks in a concrete structure.
The first reason might be from deformation in the concrete, which is caused by the forces applied to the concrete itself. We classify these forces into three main categories:
- Shear forces
Concrete is notorious for its weakness in tension compared to compression, so engineers will usually reinforce it with steel rebars. However, cracks would develop under these forces if the structural element was not sized appropriately to resist the design forces.
Here are three things to look for with deformation cracks.
- Cracks that form due to compressive forces will be observed parallel to the forces applied.
- For example, it will show as vertical cracks in a concrete column.
- Cracks that form due to tensile forces will be observed perpendicular to the forces applied.
- For example, it will show vertical cracks at the underside of a horizontal concrete beam.
- Shear cracks will typically be diagonal cracks and will occur at supports of the concrete member where the shear forces are the highest.
#2 Concrete Shrinkage
Concrete shrinkage will also cause cracks, which will occur during the drying process of the concrete. These cracks happen when the water evaporates as the concrete hardens, leading to internal forces in the concrete, creating these shrinkage cracks. For this reason, concrete is typically cured. Cured concrete involves adding moisture, such as hosing down water on the concrete or covering it with wet burlap in an effort to slow down the evaporation of the moisture in the concrete.
In addition, the engineer will typically add control joints (sometimes in slabs). These man-made joints are channels that are usually saw cut to be ¼ of the depth of the concrete and will induce the concrete to crack at these predetermined locations. These joints will result in better-looking finished concrete since the cracks will be aesthetically pleasing rather than random patterns.
#3 Steel Reinforcement Corrosion
The corrosion of the steel reinforcement may also cause cracks. By exposing steel rebars to excessive moisture, they can develop rust. Rust has a greater volume than the initial rebar, which will cause stress on the concrete and lead to cracks. When this happens, it is typically called “spalling.”
De-icing salts and marine salts can also have a very negative effect, allowing corrosion to happen at a much faster rate.
Engineers Should Assess the Effects of Cracks in Concrete Structures
To successfully understand the effects of cracks in concrete structures, you’ll need to have it examined by a structural engineer. First, they will determine the cause of the cracks and their severity. Once they provide you with an assessment, a structural engineer will be able to offer the best course of action to repair the existing damage or reinforce the concrete structure if deemed necessary.
Are You Ready to Learn What’s Causing Your Cracks?
Areté Engineers provides structural engineering services to the bridge, commercial, and residential sectors. Contact us to learn what could be causing the cracks in your concrete structure and how we can help you.