What is the primary purpose of prestressing concrete?

• To enhance the aesthetic appeal of the concrete

• To decrease the durability of the concrete

• To reduce tension cracks by placing the entire cross-section into compression

• To increase the weight of the structure

Which method of prestressing involves stretching steel in a rigid frame before placing concrete?

• Composite tensioning

• Post-tensioning

• Reinforced tensioning

• Pre-tensioning

What is a significant advantage of prestressed concrete over conventional reinforced concrete?

• It is easier to repair

• It requires less skilled labor

• It eliminates tension cracks, reducing the risk of corrosion

• It is less expensive

What is a disadvantage of using prestressed concrete?

• It is easier to construct

• It requires a lower degree of control over materials

• It is more affordable than conventional concrete

• It requires a high degree of control of materials, design, and workmanship

What type of steel is commonly used in prestressed concrete construction?

• Stainless steel

• High-strength alloy steel

• Mild steel

• Carbon steel

What is the diameter range for wires used in prestressed concrete?

• 5mm to 10mm

• 2mm to 8mm

• 8mm to 15mm

• 1mm to 5mm

What is the main characteristic of multi-wire strands used in prestressing?

• They are not commonly used

• They are made from low-carbon steel

• They are fabricated from a number of prestressing wires, usually seven

• They consist of a single wire

What is the purpose of the hydraulic jack in prestressing?

• To cure the concrete

• To cut the steel

• To apply stress to the wires

• To mix concrete

What is a requirement for steel used in pre-tensioning?

• It must be lightweight

• It must have low yield strength

• It must be non-corrosive

• It must be extensible

In post-tensioned concrete, when are the tendons tensioned?

• At the time of installation

• During the mixing of concrete

• After the concrete hardens

• Before the concrete hardens