G8 - Describe Architectural Formwork

Question 1

What is architectural concrete?

Answer 1

Finish exposed.

Question 2

Why is architectural concrete considered to be an economical choice?

Answer 2

Concrete surface is the finished surface, saving costs of cladding, maintenance costs are also reduced as concrete requires very little maintenance.

Question 3

What is the normal maximum allowable deflection allowed for architectural concrete?

Answer 3

1/400 Canada 1/360 in the USA

Question 4

What is FRP and why is it used?

Answer 4

Fibreglass reinforced plastic - used for forms who smooth and/or unusual shapes are desired.

Question 5

What are form liners used for?

Answer 5

Create textures in concrete - smooth to rough or to create decorative designs.

Question 6

What look does a ground and polished concrete surface give when coated with a sealer?

Answer 6

Mirrored cut-stone look.

Question 7

A good forming system will produce what type of architectural concrete surface?

Answer 7

Smooth, flat, uniform colour & texture. Pattern in concrete should have straight clean lines, holes spaced evenly with no honey combing.

Question 8

Who is responsible for designing forms?

Answer 8

Contractor - but approved by P.Eng

Question 9

The architectural and structural plans will show the locations and details for:

Answer 9

Construction joints, control joints, expansion joints, chamfers, rustication strips, reveals, and other design features.

Question 10

What are allowable tolerances?

Answer 10

Allowed deviation from plumb, level positioning, dimension.

Question 11

Concrete mixes for architectural concrete usually have elevated levels of what two ingredients?

Answer 11

Cement & Plasticizer.

Question 12

Why is tie spacing important?

Answer 12

Proper strength and give a pleasing appearance.

Question 13

WHat are the purposes of embedded metals?

Answer 13

Provide protection or support. Provides a welding surface as well.

Question 14

What type of release agent is normally used on architectural concrete forms?

Answer 14

Non-staining type.

Question 15

What 3 things are rustication strips normally used for?

Answer 15

Formwork seams, control joints, and construction joints.

Question 16

When should rustication strips be removed from the concrete?

Answer 16

When the concrete has sufficient strength to resist damage and the strip have had sufficient time to shrink.

Question 17

When can formwork for architectural concrete be stripped?

Answer 17

Once the P.Eng has been approved.

Question 18

How is a sand-floated finish created?

Answer 18

Within 6 hours of form stripping, surface is wetted and using a wooden hand float in circular motions, sand is worked into the surface to provide a uniform color.

Question 19

Tooling with a bush hammer will give what kind of finish?

Answer 19

A rough texture, and can be used to hide form seam lines and other minor defects.

Question 20

Grinding will give what kind of finish?

Answer 20

Smooth the surface and can be followed up with polishing for a cut-stone mirror-like finish

Question 21

Color can be added to concrete how?

Answer 21

Pigments to the mix, acid etching, using colored aggregate or adding a dry-shake color/hardener during finishing.

Question 22

Architectural ceilings may be textured:

Answer 22

Using a form liner, or other materials. May be shaped using dome pans.

Question 23

To achieve a high-quality surface, it is important for the concrete to consolidate well, to achieve this:

Answer 23

Include increased amounts of cement and plasticizer.

Question 24

For forms:

Answer 24

A high resin-coated paper-faced plywood is used, but it may also be steel, aluminum, hardboard, insulating board, fibreboard, cardboard, fibre-reinforced plastic, or thin pre-cast concrete panels.

Question 25

Formwork design needs to show sequencing in what order?

Answer 25

Forming, placing concrete, curing, stirpping and re-shoring, and any other surface treatments.

Question 26

Embedded metals are anchored to the concrete by?

Answer 26

Deformed rods, bolts, studs or bent bars.

Angle iron must be anchored every 300 mm along their entire length.

Question 27

To prevent leaking concrete formwork must be watertight how?

Answer 27

Joints between sheathing panels will need to be filled with patching material, caulked or covered.

Question 28

How must control joints be installed?

Answer 28

Perfectly plumb & level, secured to the formwork at intervals small enough to eliminate movement during the placement of the concrete.

Question 29

When are waste moulds used?

Answer 29

When there are compound curves or intricate details.

Question 30

Cutting a saw kerf in rustications trip will help:

Answer 30

Removal of wooden strips, soaking the wooden strips in form oil for a few days is a good technique as well.

Question 31

How do you place concrete for architectural forms?

Answer 31

Rate of placement needs to be moderate, stud spacing close. Vibrating one layer of placement will into the previous layer will keep the placement lines hidden.

Question 32

Architectural concrete must reach what strength before stripping?

Answer 32

10 MPa

Question 33

Rough surface treatments:

Answer 33

May just require patching or plugging of the tie holes and defects, unless tie holes are being left open as an architectural feature.

Question 34

Sandblasting surface:

Answer 34

Fine texture, but will not fix any imperfections left by the formwork.

Question 35

Tooling surface:

Answer 35

Rougher texture than sandblasting, the bush hammer chips off the surface of the concrete, exposing aggregate beneath. Bush hammer is rarely done because the amount of labour required.

Question 36

Exposed aggregate surfaces:

Answer 36

Use gap-graded aggregate, 3/8 diameter.

Question 37

Rubbed finish:

Answer 37

A rubbed finish is done after any patching has been completed and as soon as after form removal.

The entire surface is wetted and rubbed with an abrasive such as a brick

Question 38

Sand float finish:

Answer 38

Must be done within 6 hours of form stripping. The surface is wetted, and sand is worked into the surface using a wooden hand flat in a circular motion to produce a uniform color and texture.