What is the purpose of expansion joints, and what typical issues indicate deterioration?

• A. To prevent water ingress; issues include perfect sealing.
• B. To restrict movement; issues include thermal expansion.
• C. To allow longitudinal movement and accommodate thermal expansion; issues include leakage, buildup of debris, spalling, and cracks.
• D. To anchor the deck; issues include over-tightening.

Answer: (C)

Expansion joints are built to let the bridge deck move in the longitudinal direction as temperatures change and as the structure experiences loading from traffic, so the deck can expand and contract without cracking or stressing other elements. They also help keep water out by managing that movement with a proper seal. As joints age, signs of deterioration show up in several ways: leakage through the joint indicates the seal or flashing is failing; debris buildup in or around the joint can impede movement and trap moisture; spalling or chipping of concrete at the joint area reveals water intrusion and freeze–thaw damage; and cracks in the deck or around the joint often accompany seal degradation and movement issues. Together, these indicators point to compromised joint performance and the need for inspection or repair.