North Carolina General Contractors Practice Exam

Which type of joint is used to control random cracking in concrete?

1. Isolation joints

2. Control joints

3. Construction joints

4. Expansion joints

The correct answer is: Control joints

Control joints are specifically designed to manage cracking in concrete by allowing for the natural expansion and contraction that occurs due to temperature changes, moisture loss, and other environmental factors. By creating a predetermined weak point in the concrete slab, these joints direct the cracks to form in specific locations rather than randomly throughout the surface. This is crucial in maintaining the integrity and aesthetics of concrete structures, as it minimizes the potential for unsightly or structural damage. Isolation joints, on the other hand, separate the concrete from adjacent structures, allowing for independent movement. Construction joints are used to connect different sections of concrete poured at different times, ensuring a bond between them. Expansion joints accommodate movement caused by thermal expansion and contraction, but they are generally used in larger structures where significant movement is expected. Thus, while all these joints serve important purposes, control joints are uniquely designed to prevent random cracking, making them the best choice for this specific function.