Final answer:
Control joints in a slab are implemented to manage thermal expansion and contraction, ensuring that the structures can withstand temperature fluctuations without suffering damage. They function by permitting controlled cracking at predetermined points.
Step-by-step explanation:
Control joints help manage thermal expansion and contraction in a slab. These joints are strategically placed to allow the concrete to expand and contract without causing damage. The forces and pressures created by thermal stress are comparable to those in various applications. For instance, when temperature changes, materials expand or contract leading to potential structural damage if not properly managed.
Railroad tracks, roadways, and even power lines are designed with this in mind, incorporating expansion joints and allowances for sagging or stretching to withstand temperature fluctuation. Similarly, control joints in a concrete slab function by creating weak points where the concrete can crack in a controlled manner, rather than randomly, which ensures structural integrity over time and prevents hazardous buckling or cracking.