What are the two methods of pre-stressing concrete?

What are the two methods of pre-stressing concrete?

• A. Cast-in-place without any tension
• B. Pre-tensioning done at the plant, and post-tensioning done at the job site
• C. Post-tensioning at the plant and pre-tensioning at the site
• D. Bolting steel plates to the surface

Answer: (B)

Pre-stressing concrete relies on introducing compressive forces to counter tensile stresses that occur under load. There are two practical methods: pretensioning and post-tensioning. In pretensioning, the steel tendons are stretched before the concrete is cast; once the concrete cures and gains strength, the tendons are released, and their tension is transferred to the concrete, creating a compressive force throughout the member. In post-tensioning, ducts are placed in the concrete, the concrete cures, and then the tendons are threaded through the ducts, anchored at the ends, and tensioned with hydraulic jacks; grout is used to bond and protect the tendons. Pretensioning is typically done at the plant, producing prestressed elements, while post-tensioning is usually performed at the job site. Cast-in-place concrete without any tension or adding bolting steel plates to the surface do not involve pre-stressing.

Pre-stressing concrete relies on introducing compressive forces to counter tensile stresses that occur under load. There are two practical methods: pretensioning and post-tensioning. In pretensioning, the steel tendons are stretched before the concrete is cast; once the concrete cures and gains strength, the tendons are released, and their tension is transferred to the concrete, creating a compressive force throughout the member. In post-tensioning, ducts are placed in the concrete, the concrete cures, and then the tendons are threaded through the ducts, anchored at the ends, and tensioned with hydraulic jacks; grout is used to bond and protect the tendons. Pretensioning is typically done at the plant, producing prestressed elements, while post-tensioning is usually performed at the job site. Cast-in-place concrete without any tension or adding bolting steel plates to the surface do not involve pre-stressing.