Red Seal Concrete Finisher Practice Exam

What type of joint is typically used for load-bearing concrete slabs?

1. Control joints

2. Construction joints

3. Expansion joints

4. Isolation joints

The correct answer is: Expansion joints

The correct choice for the type of joint typically used in load-bearing concrete slabs is expansion joints. Expansion joints are specifically designed to accommodate the movement of concrete slabs due to thermal expansion and contraction, as well as other shifting factors like moisture changes. When concrete is poured, it naturally expands when heated and contracts when cooled. If these movements are not allowed to occur, the concrete could crack or become damaged. Expansion joints create a gap within the slab that allows for this movement while maintaining the structural integrity of the load-bearing elements. In the context of load-bearing slabs, using expansion joints ensures that the weight and stress applied to the concrete do not lead to failures or damage from stress concentrations caused by temperature changes. This is particularly important in large slabs that cover extensive areas, where significant movement can occur as temperature fluctuates. Other types of joints, like control joints, are used primarily to manage cracking caused by shrinkage, whereas construction joints are more about the intersection of two pours or sections of concrete. Isolation joints serve to separate the slab from other structures, accommodating differential movement but are not primarily designed for load-bearing considerations.