Why does concrete crack over time?
Show answer & explanation
Answer: Temperature changes cause stress
Concrete slowly dissolves away — Wrong. Concrete is chemically stable and doesn't dissolve under normal conditions. Cracking comes from physical stress, especially temperature cycles.
Temperature changes cause stress ✓ — Correct! Concrete expands when hot and contracts when cold. Daily and seasonal temperature swings create repeated stress. Add moisture (which expands when it freezes in cracks), ground shifting, and heavy loads—cracks form and spread over years. That's why expansion joints are built into sidewalks!
Gravity compresses it unevenly — Wrong. Gravity compresses concrete uniformly (downward). Cracking comes from differential movement—temperature expansion/contraction, ground settling, and freeze-thaw cycles.