Cracks on the ground are typically caused by concrete shrinkage, temperature restraints, subbase settlement, applied loads, or other issues. It usually happens if the slabs on the ground are not appropriately reinforced!
Usually, construction specialists use different structural reinforcement and nonstructural slabs for crack width control. Although there are many options to avoid cracks on the ground, this article will focus on using steel reinforcing bars and welded wire reinforcement to control the damages.
What Is Steel Reinforcing Bars and Welded Wire Reinforcement?
Steel reinforcing bars and welded wire reinforcement is a designed approach that helps control crack widths by restricting crack growth. The steel reinforcement is used to tie different concrete elements together. In contrast, the welded wire reinforcement is used for reinforcing floor slabs with a series of bars that run perpendicular to each other in a grid layout.
If random cracks occur, the approach becomes active, keeping the structure fairly tight because of the limited joint space and low concrete shrinkage.
What Are the Different Crack Control Options?
There are two options when it comes to controlling cracks in slab-on-ground:
1. Install Contraction Joints – Contraction joints, often called control joints, minimize random cracking. It does not control crack widths but instead controls the cracking location by inducing cracks at predetermined locations.
Most designers use load-transfer devices, including steel dowels, plates, or continuous reinforcement through contraction joints to ensure positive load transfer and restrict differential vertical movements across joints.
2. Install Steel or Welded Wire Reinforcements – Installing reinforcements allow slabs to crack randomly but will control the crack widths with the help of steel bars or welded wire. However, this option does not prevent the crack location, and the cracking occurs randomly, forming numerous tightly held together cracks.
Why Does Location of Reinforcement Matter?
Keeping the reinforcement in place is critical to the stability and structure’s performance. Therefore, designers must place down reinforcements as shown on the placing drawing to ensure the quality and firmness of the ground.
The fundamental reasons why the location of the reinforcement matter is because:
1. Optimal location minimizes movement during concrete placing and finishing.
2. Shrinkage and temperature originate at the slab’s surface, so it is essential to position the reinforcement in the upper third of the slab thickness.
3. Cracks are wider at the surface and narrow with depth, so reinforcements should never be positioned below the slab’s mid-depth.
4. There is a tendency for saw cutting, so it should be placed low enough.
5. The Wire Reinforcement Institute recommends placing steel placement 2 inches below the surface or within the upper third of the slab thickness, whichever is close to the surface.
6. Welded wire reinforcement requires closer support spacing.
7. It should never be placed on the ground and pulled into position after concrete placement to avoid improperly positioned reinforcement.
Proper placing and supporting reinforcement can help do away with ground cracking. Your designer’s advice will significantly affect how you can prevent ground cracking from happening—which is why it’s crucial to have an experienced partner when it comes to establishing a structure’s design.
If you are looking for a structural steel specialist in Queensland, Phoenix Reinforcing offers a full delivery service specializing in reinforcing sales, scheduling and estimating, reinforcing productions and cage fabrication, decorative concrete products, and more! Contact us today and avail of our service!