FORMWORK

Question 1

Discuss the factors that affect pressure on formwork

Answer 1

Rate of Placement: Faster placement increases pressure due to the weight of the concrete above.
Concrete Weight: Heavier concrete exerts more pressure
Temperature: Higher temperatures can reduce concrete viscosity, increasing lateral pressure.
Concrete Mix Characteristics: The mix’s slump (fluidity) and the use of admixtures can affect pressure.
Vibration: Vibration helps compact concrete but can also temporarily increase pressure.
Ambient Conditions: External conditions like wind can impact the formwork pressure

Question 2

Discuss the properties, types and the application of formwork release oils

Answer 2

1. Significance
   Facilitate the easy removal of formwork without damaging the concrete surface.
2. Properties
   Nonstick (thus preventing adhesion)
   Surface Finish (smooth concrete achieved)
   Easy applicaton
   Facilitate easy removal of formwork
   Compatability (form face)
3. Types
   Mineral oil based
   Emulsion of water (oil based)
   Chemically active (ingredients react with concrete to form a layer)
   Wax emulsion
4. Application
   Apply on: clean formwork, before reinforcement, each time formwork is used etc.

Question 3

Joints

Answer 3

1. Define
   Planned and intentional joints placed for different purposes.
2. Types
   Expansion
   Control
   Contraction
3. Purpose
   * Control Cracks (control where cracks form in concrete, directing them to planned locations)
   * Ease of Construction (Joints divide large pours into manageable sections)
   * Expansion and Contraction (joints allow for the natural expansion and contraction of concrete, preventing damage from thermal stress).
   *Aesthetic Purposes (they can enhance the appearance of the concrete surface, more
   organized)

Question 4

Discuss the preparation of a cold joint

Answer 4

1. Define
   Occurs when a break or delay in the concrete pouring process
2. Effects
   Batches of concrete that don’t bond as well as they should
   Creates a weak spot in structure

Question 5

Discuss the requirements for formwork

Answer 5

Strength (withstand the weight, concrete pressure, workmen)
Rigid
Accuracy
Imparts required surface finish
Tight joints to prevent leakage
Easy and quick erection and dismantling (striking)

Question 6

Different types of formwork

Answer 6

1. Timber
   Provide wide range of surface finish and can be cut on site
   Short life span
2. Steel
   Long lasting and resusable
   heavy and expensive

Question 7

Describe when formwork can be struck and to care for formwork

Answer 7

Striking according to:
Type of member
Direction of form face
Concrete properties
Curing conditions

Care of formwork
KEEP CLEAN!!!! (Residue after use removal, brush before use or wipe etc.)
Repair defects
Store properly
Protect and keep dry
Maintenance

Question 8

Define construction and emergency joints, cold joint and a water stop

Answer 8

1.Construction
Planned joints where fresh concrete meets concrete that has already set.
Used to divide large pours into manageable sections and accommodate construction schedules.

2. Emergency Joints
   Unplanned joints created due to unexpected interruptions in the concrete pouring process.
   To manage the unplanned break and ensure structural integrity.
3. Cold Joint
   Occurs when there is a delay between concrete pours, and the first batch starts to set before the next is poured.
4. Water stop
   barrier within construction joints to prevent water from passing through the joint.

Question 9

Discuss the position of joints in a structure

Answer 9

1. Control Joints
   Placed at regular intervals in slabs and pavements.
2. Expansion
   Different positions
3. Cold
   Occur wherever there is an unintended break.
4. Construction
   Different positions