403A Concrete Formwork 3

Question 1

What is a kicker (or brace) in wall formwork and where is it positioned?

Accepted Answer

A diagonal brace from the top of the form to an anchor on the ground to prevent the form from tipping

Answer

Kickers are diagonal braces running from the upper portion of the form down to ground anchors or floor anchors. They prevent the form from tipping outward under the lateral pressure and weight of the concrete and prevent overturn.

Question 2

What is the purpose of a grout stop (or base seal) at the bottom of a wall form?

Accepted Answer

To prevent cement paste from leaking out at the form base during the pour

Answer

Fresh concrete is fluid and cement paste can leak out through gaps at the base of the form. A grout stop (foam strip, rubber seal, or mortar) seals the bottom to prevent leakage, which would create voids, honeycombing, and grout loss at the bottom of the wall.

Question 3

What is 'honeycombing' in concrete and what causes it?

Accepted Answer

Voids in the concrete surface caused by inadequate consolidation or cement paste leakage

Answer

Honeycombing appears as rough, porous, void-filled areas on the concrete surface after form stripping. It is caused by inadequate vibration (air and voids not consolidated), concrete mix that is too stiff, reinforcing steel that blocks flow, or leakage of cement paste through form joints.

Question 4

What is the difference between a control joint and an expansion joint in a concrete slab?

Accepted Answer

Control joints are tooled or sawn to induce cracking at planned locations; expansion joints allow thermal movement between separate concrete sections

Answer

Control joints (contraction joints) are weakened planes that cause the concrete to crack at a predetermined location rather than randomly — they do not allow movement. Expansion joints use a compressible filler to allow adjacent slabs to move toward each other without cracking.

Question 5

What is the maximum allowable slump for structural concrete placed in wall forms under normal conditions per CSA A23.1?

Accepted Answer

100 mm

Answer

CSA A23.1 typically specifies slump limits of 80-100 mm for wall concrete without superplasticizers. Higher slump increases segregation and bleed water, reducing concrete quality. Actual slump limits depend on the mix design and project specifications.

Red Seal Carpenter 403A Practice Test

Red Seal Carpenter 403A Practice Test

403A Concrete Formwork 3