North Carolina General Contractors Practice Exam

What is the minimum thickness of control joints relative to slab thickness?

1. 1/8 of the slab thickness

2. 1/4 of the slab thickness

3. 1/2 of the slab thickness

4. Equal to the slab thickness

The correct answer is: 1/4 of the slab thickness

The minimum thickness of control joints relative to slab thickness is vital for maintaining structural integrity and managing crack formation in concrete slabs. The correct answer indicates that control joints should be at least one-quarter of the slab's thickness. This guideline helps ensure that the joint effectively accommodates movement and shrinkage as the concrete cures. By having control joints at this minimum thickness, it allows for a sufficient depth at which the slab can naturally crack along the joint lines rather than in an unpredictable manner across the slab surface. This is particularly important in larger pours of concrete, where temperature changes and drying can cause significant movement and stress. Control joints that are too shallow may not effectively manage the stresses placed upon the slab, potentially leading to surface cracking that can compromise the structural and aesthetic aspects of the concrete. Other options suggest either a lesser or greater ratio, which does not align with the established guidelines for effective control joint design.