A concrete footing is being prepared, and the rebar schedule calls for 15M reinforcing bars to be placed with a minimum concrete cover of 75 mm from the bottom and sides. What is the most effective way to ensure the bottom reinforcing steel maintains the specified cover during concrete placement?

Question: A concrete footing is being prepared, and the rebar schedule calls for 15M reinforcing bars to be placed with a minimum concrete cover of 75 mm from the bottom and sides. What is the most effective way to ensure the bottom reinforcing steel maintains the specified cover during concrete placement?

Answer options:

• Suspending the rebar using wires attached to the formwork.
• Placing the rebar directly on the excavated soil. ✅ Using pre-cast concrete blocks (dobies or chairs) of the appropriate height.
• Relying on the concrete slump to lift the rebar into position.

Correct answer: Using pre-cast concrete blocks (dobies or chairs) of the appropriate height.

Explanation: Pre-cast concrete blocks, also known as chairs or dobies, are specifically designed to support reinforcing steel at the correct height, ensuring the specified concrete cover is maintained from the bottom of the footing. Suspending with wires is less reliable and difficult to adjust, placing directly on soil eliminates cover, and concrete slump cannot reliably lift and hold rebar in place.