Concrete Formwork - PowerPoint PPT Presentation

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Concrete Formwork

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Concrete Formwork General Requirements Safe must hold concrete in place until cured. Economical provide desired shape and surface texture Formwork usually cost ... – PowerPoint PPT presentation

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Title: Concrete Formwork


1
Concrete Formwork
2
  • General Requirements
  • Safe must hold concrete in place until cured.
  • Economical
  • provide desired shape and surface texture
  • Formwork usually cost more than the concrete

3
  • Typical formwork
  • Can be
  • wood
  • Steel
  • Aluminum
  • Must be braced to withstand load (concrete weighs
    150pcf)

4
  • Wall form F 11-18
  • Double wales used above and below ties to allow
    tie to be secured
  • Also need a spreader to keep forms correct
    distance apart
  • Need to have good bracing at foot of form
  • Ties F 11-19
  • Most common can be broken off just inside
    concrete allows for patching

5
  • Column Forms
  • Use column clamps for support/bracing
  • May have windows to making pouring easier
  • F 11-20
  • Slabs
  • F 11- 21 -gt 11-25

6
Construction Practices
  • Forms need tight joints
  • Forms need to be aligned and checked for
    alignment during pour
  • Dont forget uplift on some types of forms
  • Dont drop concrete more than 5
  • Dont vibrate previously poured concrete too
    deeply could cause form failure
  • Carefully remove forms dont want surface
    damage

7
Expansion and control joints
  • Permit differential movement in concrete shapes
  • Concrete shrinkage, temperature change, moisture
    change, settlement
  • Isolate interior columns from floor slab cut
    around column

8
Formwork safety
  • Pg 321

9
Reinforcing Steel
  • Reinforcing bars
  • Usually deformed (manufactured with ridges to
    increase bond with concrete)
  • Can be plain or epoxy coated
  • Sized by 1/8th inch and strength of steel
  • T 11-1, F 11-28

10
Reinforcing Steel
  • Welded wire fabric
  • Common for slabs
  • Smooth or deformed wire
  • WWF is identifier
  • WWF 6x6-4.0x4.0 is a welded wire fabric with 6
    inch spacing longitudinally and transversely made
    of W4 size (0.04 x section area) wire

11
  • Spirals (for columns)
  • 3 standard sizes 3/8 inch, ½ inch, 5/8 inch
    diameter rods
  • Sprial diameters (outside to outside) 12 minimum
    to 33 max
  • Pitch from 1.75 3.25 (distance from center to
    center of rod)

12
Placing Reinforcing
  • Rebar goes in areas of tension
  • F 11-29
  • Need to protect rebar from corrosion fire and
    weather
  • Pg 325 gives min cover
  • Minimum clear distance between parallel bars in
    columns 1.5 or 1.5 x max aggregate size
  • For other shapes 1 or 1.333 x max aggregate size

13
Placing Reinforcing
  • Rebars kept in place by ties
  • F 11-30, 11-31

14
QC
  • Common deficiencies
  • Pg 329
  • Inspection and Testing
  • Usually concrete is a fast paced activity
  • Need to inspect product from stockpile to
    placement and then test for strength, air
    entrainment, beam flexure
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