Red Seal Concrete Finisher Practice Exam

What is one of the main functions of control joints in concrete?

1. To increase the load-bearing capacity

2. To minimize cracking by allowing for expansion and contraction

3. To support the formwork

4. To enhance the texture of the surface

The correct answer is: To minimize cracking by allowing for expansion and contraction

Control joints serve a critical purpose in managing the stresses that can lead to cracking in concrete. They are specifically designed to minimize cracking by allowing for the natural expansion and contraction of the concrete as it cures and reacts to temperature changes and moisture loss. Concrete is a rigid material that does not flex; as it heats up, it expands, and as it cools, it contracts. Without properly placed control joints, this movement can lead to random cracking, which can compromise the structural integrity and appearance of the concrete. By strategically placing control joints, the concrete is allowed to crack in a controlled manner along these joints, helping to maintain the overall integrity of the slab while minimizing visible damage.