What is the purpose of control joints in concrete flatwork?

The purpose of control joints in concrete flatwork primarily focuses on accommodating thermal expansion and contraction. As concrete cures and changes temperature, it naturally expands and contracts. If these movements are not properly managed, it can lead to cracking. Control joints are strategically placed in a concrete slab to create a predetermined weak point, directing where cracks are likely to occur. This way, any stress from movement is absorbed and mitigated, allowing the slab to maintain integrity and functionality over time.

While enhancement of strength, improvement of appearance, and additional support in high-load areas are important aspects of concrete finishing and design, they do not align with the primary role of control joints. Their design does not significantly impact overall strength, nor are they intended for purely aesthetic purposes or to support heavy loads. Instead, the effective use of control joints helps ensure that the concrete structure can endure the physical effects of temperature variations without developing random cracking, which can compromise both appearance and performance.