How is the expansion joint spacing for a concrete slab determined?

The spacing of expansion joints in a concrete slab is determined primarily by the length and temperature variations that the slab will experience. While the answer indicates a uniform 10-foot spacing, the correct method for determining expansion joint spacing typically involves various factors including the thickness of the slab, the anticipated temperature changes, and the specific project requirements.

Option A suggests a one-size-fits-all approach of every 10 feet in all directions, which can serve as a basic guideline in some cases but may not take into account the actual conditions and requirements of a specific project. Proper engineering practices recommend customizing expansion joint placement based on the slab thickness and the expected thermal expansion/contraction.

Answer C, referring to the thickness of the slab, aligns more accurately with best practices; typically, the spacing can be influenced by the slab thickness, as thicker slabs may require fewer joints compared to thinner ones. Moreover, environmental factors and load considerations are essential in determining the appropriate spacing for the joints to prevent cracking and material failure.

In practice, a tailored approach based on multiple conditions typically yields better results than a strict rule like the one presented in option A.