What factors cause tension stress in concrete?

• A. Drying shrinkage, weight, Temperature changes
• B. Temperature changes only
• C. Moisture and humidity changes
• D. External loads

Answer: (A)

Tension stresses in concrete occur when movement or forces try to pull the material apart, and concrete isn’t strong in tension, so those stresses show up as cracking or crack-prone zones. The three main ways this happens are: drying shrinkage, temperature changes, and bending from weight or other loads.

Drying shrinkage happens as concrete loses moisture and tends to shrink. If the structure or joints restrain that shrinkage, tensile stresses develop in the concrete and cracks can form. Temperature changes cause the concrete to expand or contract. When movement is restrained, these thermal movements create tensile (and sometimes compressive) stresses in different parts of the member, contributing to cracking if not managed. The weight of the structure itself, along with other external loads, can bend members so that the far side is put into tension; that tension is carried by the concrete in the tension zone, especially before reinforcement or after cracking.

So the best answer includes all three factors—drying shrinkage, weight (which induces bending and tension on the tension face), and temperature changes—because together they cover the common ways concrete experiences tension stresses. Other options miss one or more of these mechanisms, so they don’t capture the full picture.