403A Formwork — Questions and Answers
Question 1: What is the primary purpose of formwork in concrete construction?
- To reinforce the concrete after it cures
- To shape and support wet concrete until it gains sufficient strength (Correct answer)
- To insulate the concrete from temperature changes
- To prevent moisture from entering the concrete mix
Correct answer: To shape and support wet concrete until it gains sufficient strength
Formwork is a temporary mould used to shape and support wet (plastic) concrete until it hardens and gains sufficient strength to support its own weight and applied loads. It defines the shape, size, and surface finish of the concrete element.
Question 2: What is the maximum recommended rate of concrete pour for wall forms to minimize lateral pressure?
- 0.5 m per hour
- 1.0 m per hour (Correct answer)
- 2.0 m per hour
- 3.0 m per hour
Correct answer: 1.0 m per hour
A common recommended pour rate for wall forms is approximately 1.0 m per hour, which allows the concrete at the bottom to begin setting and reduces the maximum lateral pressure on the forms. Higher pour rates require stronger formwork.
Question 3: What is the purpose of form ties (snap ties) in wall formwork?
- To connect the formwork to the foundation
- To hold opposing form walls at the correct spacing and resist concrete pressure (Correct answer)
- To provide attachment points for scaffolding
- To create expansion joints in the finished wall
Correct answer: To hold opposing form walls at the correct spacing and resist concrete pressure
Form ties (snap ties) extend through the wall thickness to hold the two opposing form faces at the correct spacing while resisting the lateral pressure exerted by the wet concrete. They break off at the form face after stripping.
Question 4: When is it generally safe to strip wall formwork for a standard residential foundation in moderate Canadian temperatures?
- Immediately after pouring
- 12 hours after pouring
- 24 to 48 hours after pouring (Correct answer)
- 7 days after pouring
Correct answer: 24 to 48 hours after pouring
Wall formwork can typically be stripped 24 to 48 hours after pouring in moderate temperatures (above 10°C), as the concrete will have gained enough strength to be self-supporting. Cold weather may require longer curing times before stripping.
Question 5: What is a keyway in footing formwork?
- A locking mechanism for form panels
- A groove formed in the top of a footing to interlock with the foundation wall above (Correct answer)
- A drainage channel at the bottom of the footing
- A removable strip for creating expansion joints
Correct answer: A groove formed in the top of a footing to interlock with the foundation wall above
A keyway is a continuous groove formed in the top surface of a concrete footing. When the foundation wall is poured on top, concrete fills the keyway, creating a mechanical interlock that resists lateral movement.
Question 6: What type of release agent is applied to formwork before placing concrete?
- Concrete adhesive
- Form oil or release agent to prevent concrete from bonding to the forms (Correct answer)
- Waterproofing membrane
- Anti-corrosion primer
Correct answer: Form oil or release agent to prevent concrete from bonding to the forms
Form oil or release agent is applied to the form surfaces before concrete is placed. It prevents the concrete from bonding to the forms, allowing clean stripping and extending the life of the formwork materials.
403A Formwork
What is the primary purpose of formwork in concrete construction?