Which statement best describes pre-tensioned reinforcing in construction?

Which statement best describes pre-tensioned reinforcing in construction?

• A. Concrete is poured before steel is stretched.
• B. Steel strands are stretched between anchors before concrete is placed, creating a tensile force in the steel.
• C. Reinforcement is embedded in timber.
• D. The concrete is poured and allowed to cure without any tension in steel.

Answer: (B)

Pre-tensioned reinforcing uses the steel reinforcement in a way that introduces a prestress before the concrete is cast. The steel strands are stretched between fixed anchors, creating a tensile force in the steel while it’s held in that stretched state. Concrete is then poured around these tensioned strands and cured. When the concrete gains strength and the anchors are released, the tension in the steel is transferred to the concrete, putting the concrete in compression. This early application of tension is what gives pretensioned systems their advantage in resisting cracking and bending. The other ideas don’t describe pretensioning: embedding reinforcement in timber isn’t applicable here, pouring with no tension misses the prestress concept, and stressing after pouring describes post-tensioning rather than pretensioning.

Pre-tensioned reinforcing uses the steel reinforcement in a way that introduces a prestress before the concrete is cast. The steel strands are stretched between fixed anchors, creating a tensile force in the steel while it’s held in that stretched state. Concrete is then poured around these tensioned strands and cured. When the concrete gains strength and the anchors are released, the tension in the steel is transferred to the concrete, putting the concrete in compression. This early application of tension is what gives pretensioned systems their advantage in resisting cracking and bending.

The other ideas don’t describe pretensioning: embedding reinforcement in timber isn’t applicable here, pouring with no tension misses the prestress concept, and stressing after pouring describes post-tensioning rather than pretensioning.