Reinforcing concrete & cover

It is important when inspecting reinforcing bars that they are clean and free of loose rust. They should be placed in accordance with the structural engineers drawings, usually made up of main and secondary bars. When inspecting reinforcement you have to make sure that the laps are sufficient, and it’s usually 40x the diameter of the bar being used.

An appropriate amount of concrete cover is required for the reinforcement of concrete, and this should be specified by a structural engineer. The following guidance should be followed;

– Concrete in direct contact with the ground – Min cover 75mm

– External applications, like shuttered walls – Min cover 50mm

– Floor slabs & where concrete is cast onto a membrane – Min cover 40mm

– Concrete over binding concrete – Min cover 40mm

– Internal conditions – Min cover 25mm

Plastic or steel spacers can be used in the reinforcing process. The thickness and depth of the concrete spacer should not exceed 50mm x 50mm. Spacers should be placed at max 1m centres. Reinforced concrete should be compacted using a vibrating poker. Tamping of floors by hand is acceptable for floor slabs that do not exceed 150mm thickness. Admixtures can be used if stipulated as part of the original design specification. Plasticisers can be used to improve concrete adhesion. Air entraining agents can be used to increase the air void volume and accelerators used to improve curing time.

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