Farmwork shuttering

CONTENTS
• DEFINITION OFFORMWORK
• REQUIREMENTS OFA GOOD FORMWORK
• CATEGORIES OF FORMWORK
• TYPES OFFORMWORK
• PROCESS OFFORM WORKCONSTRUCTION
• DESHUTTERING
• FAILURE OF FORMWORK
• SAFETY PRECAUTION

DEFINITION OF FORMWORK
Formwork is amould or open box, like container into
which fresh concrete is poured and compacted.
When the concrete is set, the formwork is removed and a
solid mass is produced in the shape of the inner face of
the formwork.
It should be capable of carrying all imposed dead and
live loads apart from its own weight.

REQUIREMENTS OF AGOOD FORMWORK
Materials should be cheap and reusable.
Swelling and shrinkage should be minimum.
Surface should be smooth, and afford easystripping.
Light in weight , so that easy to transfer.
It should be practically water proof , so that it should not absorb
water from concrete.
The material of formwork should not warp or get distorted when
exposed to the elements.
The joints in the formwork should be tight against leakage of
cement grout.
 Deflection should be minimum.

CATEGORIES OF FORMWORK
CONVENTIONAL: The formwork is built on site out of timber or moisture -
resistant particle board. It is easy to produce but time -consuming for larger
structures, and the plywood facing has a relatively short lifespan. It is still used
extensively where the labour costs are lower than the costs for procuring
reusable formwork.

M ODERN-DAY FORMWORK :This formwork system are
mostly modular, which are designed for speed and
efficiency. The main types of formwork systems in used
now are
 Table form/flying formwork
 System column formwork
 Slip formwork
 Tunnel formwork

ENGINEERED/PRE-FABRICATED FORMWORK: This formwork is
built out of prefabricated modules with a metal frame (usually steel
or aluminium) and covered on the application (concrete) side with
material having the wanted surface structure (steel, aluminium,
timber, etc.).

Major objectives considered in formwork
 Quality
 Safety
 Economy

Quality:
Forms must be designed and built with sufficient
stiffness and accuracy so that the size, shape, position, and
finish of the cast concrete are maintained .
Safety:
Forms must be built sufficient strength and factor of
safety so that they have the capable of all supporting
loads .
Economy:
Forms must be built efficiently, minimizing time and
cost.

TYPESOF FORMWORK MATERIALS
TIMBER
STEEL
PLASTIC
ALUMINIUM

TIMBER FORMWORK:
Most common material used for
bracing the member, hence called
as the traditional formwork.
Can easily be cut to size on site.

ADVANTAGES OF TIMBERFORMWORK:
 Easy handling because its light weight.
 Easy to disassemble.
 Damaged parts can be replaced with new one.
 It has good thermal insulation which makes it
useful to be used in colder regions.
 Reduced site labour.
 Can be built to exceed 60 year design life.

DISADVANTAGES OF TIMBERFORMWORK:
 Can’t be used for long, have limited reuse.
 If timber is dry, it will absorb moisture from wet
concrete which could weaken the resultant concrete
member.
 Timber with high moisture content (more than
20% moisture content), wet concrete will
shrink & cup
leading to open joints & leakage of grout.

STEEL FORMWORK:
Steel forms are stronger,
durable and have longer life
than timber formwork and
their reuses are more in
number.
Steel forms can be installed
and dismantled with
greater ease and speed.

ADVANTAGES OF STEELFORMWORK:
 Very strong and able to carry loads
 Easy to be fixed.
 Uniform size and surface.
 Can be used for more number of times.
 More durable than timber formwork.
 No shrinkage of formwork occurs.

DISADVANTAGES OF STEELFORMWORK:
 More expensive than wood.
 Due to high weight handlingis difficult.
 Excessive lossof heat.
 Limited size and shape.

ADVANTAGES OF PLASTICFORMWORK:
 Light weight.
 Reusable.
 Chemical resistant.
 Fungus and termites resistant.
 Can be easily cut and nail by using wood working.
 Damages on the formwork can be easily removed.
 Very useful for complex shaped and special features.

DISADVANTAGES OF PLASTICFORMWORK:
 Expensive at first.
 Load carrying capacity low.
 Damage the plastic by the heat.

ALUMINIUM FORMWORK:
Aluminium is strong and light,
and consequently fewer,
supports and ties are required.

ADVANTAGES OF ALUMINIUM FORMWORK:
 Monolithic crack free structures.
 Doesn’t require timber or plywood for construction
activities.
 Casting of walls and slabs possible simultaneously.
 Doesn’t required skilled labour.

DISADVANTAGES OF ALUMINIUM FORMWORK:
 Architectural changes are not possible on the structure.
 Due to the tremendous speed of construction, working
capital finance needs to the planned in advance.

PROCESS OF FORMWORK
CONSTRUCTION
FORMWORK FOR VARIOUS STRUCTURAL MEMBERS

FORMWORKFOR WALL
It consists of
-Timber sheeting
-Vertical posts
-Horizontal member
-Rackers
-Stakes
-Wedges

Wall formwork and its components

FORMWORK FOR COLUMN
Itconsistsof
-Side and end planks
-Yoke
-Nuts and bolts
Two end and two side planks are joined by
the yokes and bolts.

Erection s equence for a column:
cleared fPrior to positioning column formwork check that steel for the columnhas been inspected and
or casting.
- Position formwork for the column from predeterminedgrids.
- Plumb formwork both ways and securely support using adjustable steel props.
- The propping angle should be 45° to the floor.
- Ensure the steel props are safely secured to the column formwork and
the floor, and that adjustment for pushing and pulling isoperational.
- Set out the positions of column clamps from a storeyrod.
- Transfer the column clamp positions from the storey rod onto columnformwork.
- Use nails to support the arms of column clamps while wedging.
- Position and wedge the bottom, middle and top clampssets.
- Check the formwork at the top for square.
- Position and wedge the remainder of the columnclamps.
- Using a plumb bob suspended from a gauge block plumb the column
 When all the column formwork is securely propped a final check must be ma
de for plumb and column alignment before and immediately after the
concrete has been poured and vibrated.

Formwork for staircase
 Points to consider when designing
staircase formwork:
Stair formwork must support the weight
of concrete.
Because of the slope of the stair, some of
the force is transmitted to the sideways. All
formwork must be well tied together to
prevent sideway movement.

Erection sequence for a beam:
 Marking out and setting height for formwork
 Assemble and position props, adjustable head jacks, formworks,
bearers and spreaders.
 Construct and erect sidewalls and beam soffit.
 Position of sole plates.

DESHUTTERING
“DESHUTTERING” means the process of removing the shuttering.
Order and method of removing formwork:
Shutte ri ng formi ng verti cal fac es of wal ls, beams
and colum ns sho ul d be re moved firs t. Shutte ri ng
form ing soffit to slab sho ul d be re moved ne xt.
Shutte ri ng formi ng soffit to beams or othe r
he avy loade d members sho ul d be re moved in the
end.

Time of removal of formwork:
Sl
.
N
o
Structural Member
OPC
(Ordinary Portland
Cement)
Rapid
Hardening
Cement
1 Beam sides, walls & Columns 2-3 Days 2 Days
2 Slab (Vertical Supports remains intact) 4 Days 3 Days
3 Slab (Complete Formwork removal) 10 Days 5 Days
4 Beams (Removal of Sheeting,
Props remains intact)
8 Days 5 Days
5 Beams & Arches (Complete formwork
removal) (up to 6 m span)
14 Days 5-8 Days
6 Beams & Arches (Complete
formwork removal) (more than 6 m
span)
21 Days 8-10 Days

Cost of formwork:
For normal works formwork costs about 30 -40% of
the concrete cost.

 Generally someunexpectedeventcausesone member
tofail,thenothersbecomeoverloaded ormisaligneda
ndtheentireformwork
structurecollapses.
 Vibration.
 Inadequatebracing.
 Unstablesoilunderfoundations.
 Inadequatecontrolofconcrete placement.
 Lackofattentionofformworkdetails.
 Inadequatecrossbracingandhorizontal
bracingofshores.
 Passingtraffic.
 Movementof workers andequipmenton the
formwork.

SAFETY PRECAUTION
 Mate ri al us ed for the construc tion of form wo rk must ful fill the
specificati on.
 Formwo rk is fixed firml y and pro perl y.
 Construc tion are a must be pro tected to pre vent vandal ism of
form wo rk .
 Warni ng sign must be put up at the are a whe re the form wo rk
is fixed to pre vent entranc e of people that may dam ag e the
form wo rk .
 The form wo rk must be inspected before the conc re te is po ure d.

Farmwork shuttering

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Farmwork shuttering