Expansion joints in concrete are designed to accommodate movement caused by which factor?

• A. Shrinkage
• B. Temperature-related expansion
• C. Load-induced bending
• D. Soil settlement

Answer: (B)

Expansion joints are designed to let concrete slabs change size as temperatures change. When the temperature rises, concrete expands; if that expansion is restrained, stresses build up and can lead to cracks or buckling. The joints provide space for this movement so the slab can freely expand and later contract as it cools.

Shrinkage from drying and moisture loss does cause cracking, but that's typically managed with other joint types (like control joints) that are intended to control where cracks form rather than to absorb thermal movement. Load-induced bending and soil settlement involve different structural considerations (reinforcement and foundation stability) and aren’t the primary purpose of expansion joints.