Rebar, which provides reinforcement for the concrete, needs to be embedded to the proper depth to provide the appropriate strength to the structure. Rebar chairs and concrete spacer blocks prop up the bars separating them from the formwork so that the rebar is secured in the correct position.
Bar Chairs
Bar chairs are the most common; they hang the rebar at a specified height so that it is embedded as the concrete is being poured. They can be metal, plastic or any non-corrosive material. They are easy to install and lightweight.
In recent times, however, concrete spacer blocks are used instead of plastic chairs when handling heavy weights.
Concrete Spacer Blocks
Concrete spacer blocks are concrete blocks with galvanised wire that are specially engineered to carry high load capacities.
Spacers are a crucial tool in any construction project. They maintain the reinforcement in the correct position, ensuring that the placement of the rebar does not alter during the concrete pour.
Concrete spacer blocks are square concrete block chairs with integrated galvanised tie wire that can be used in most projects to support the rebar ensuring compliance. Moreover, they are also heat resistant and stable.
Concrete spacer blocks are available in block heights ranging from 25mm to 100mm.
Benefits of Concrete Spacer Blocks
In some instances, the weight of the reinforcement steel bars may be too heavy for a plastic chair to hold them in position. The mass of the steel can crush the chair and cause the steel bar to displace, which jeopardises structural integrity. If this is the case, concrete spacer blocks can hold greater weights without being displaced, they will successfully hold the steel in place while the concrete is being poured.
Concrete spacer blocks are most commonly used in civil and infrastructure construction projects like road works as they require reinforcement bars with a large diameter, which the plastic chairs will be unable to hold. If this is the case, concrete spacer blocks help to maintain a specified height between the ground surface and the reinforcement steel bars.
Finally, the base of concrete spacer blocks is shaped such that they don’t move during construction, providing the stability required.
Conclusion
Spacers and chairs provide the much-needed support to the reinforcement bar ensuring proper concrete cover. Sometimes, the bars can be too heavy for the plastic chairs, in which case, concrete spacer blocks are used.
Due to their strength and high load resistance, you will find them commonly used in civil projects such as road works, dams, etc.