COMPLETE GUIDELINES, METHODOLOGY, TOLERANCE, AND CHECKLIST FOR FORMWORK
Formwork is also a kind of temporary structure whose purpose
is to support its own weight and that of freshly placed concrete as well as the
construction live loads including materials, equipment and workmen. Formwork as
a temporary structure is desired to safely support the concrete until it gains
adequate strength to stand on its own.
Definition of formwork
According to IS: 6461 (Part 5)–1972, formwork is a complete
system of temporary structure built to contain fresh concrete so as to form it
into the required shape and dimensions and to support it until it hardens
sufficiently to become self-supporting. It includes the surface in contact with
the concrete and all the necessary supporting structure.
as a temporary structure but very important to give full attention , its very important to execute the preparation the erection and di-shuttering of formwork system because entire structure its finish and it faults mainly depends upon the proper formwork system.
this article provides you the complete guidelines for design, construct, erect, maintain and stack the formwork properly after its work is completed.
A) REQUIREMENTS.
1. Form work shall be provided as per required. Shape, size and finish
2. Rigidity and durability during placing (tine & levels)
3. Rigidity and durability for receiving fresh concrete.
4. Easy removal without disturbing concrete.
5. Provide easy access for handling and placing.
B) CODES FOR REFERENCE.
1. IS 303 Specification for plywood for purpose
2. IS 456 Code of practice for construction and design for reinforced concrete.
C) SAFETY REQUIREMENTS.
Displaying safety provisions: These safety provisions shall be brought to the notice of all concerned by display on a notice board at prominent place at the work spot. Precaution shall be taken to ensure safety to all workers and staffs. Use of helmets and safety shoes, safety harness shall be mandatory.
Safety training / inductions shall be organized time to time.
Safe scaffolding system shall be provided with adequate access for concrete works
Workers shall work with required safety measures such as
safety belt, helmet etc.
.
D) MATERIALS TO BE USED.
Material used in formwork shall be combination of timber, plywood, steel adjustable props, steel plates, or specially designed and manufactured mould out of structural steel members.
Use shall depend on its location, type, of finish specified
and subject to acceptability
MS bolts, nuts, clamps, of required standard shall be used. Use of these shall not be harmful to concrete and shall be easily removable or if left in concrete shall be inserting to concrete in all respect.
Form release Agent
Emulsion and oil or chemical agent being used shall not
react with reinforce concrete at any stage, No chemical reaction shall take
place which may be harmful to reinforcement concrete for its durability
strength. These shall not produce any stain and shall not stick to concrete
surfaces which will reduce further bonding strength of masonry mortar, painting
etc.
E) DEPLOYMENT OF LABORS.
Carpenters
Carpenter Helpers
Scaffolds
F) IMPLEMENTATION.
a) Erection.
1. Erection of formwork may be from pre-mould, pre-fabricated, pre-assembled plates or forms reasonable enough to transport and erect at site to correct line and level at site. Supports shall be firm and maintained in position by nails, cross bracing, tie rods, locking bolts and nuts. It shall be rigid and stiff so as to retain its shape during and after concreting. For the starters of column & retaining wall cleat angle shall be welded to the additional reinforcement bar inserted in the wet concrete. After the formwork DE shuttered the cleat angle shall be thoroughly to remove the corrosion & protection coating as directed by client shall be applied.
2. Joints shall be water-tight and no cement slurry shall be allowed to slip through. In joints foamed tapes shall be used.
3. Pre-fabricated or site forms shall be assembled, so as to de-shutter without any jerk to the green concrete. For this double wedges shall be used. Wedges shall be nailed, the heads reasonably left out, allowing easy removal while de-shuttering.
4. On site fabricated form shall be of sufficient thickness and with the required supporting runners in either direction. Supporting runners shall be standardized in size for easy replacement and universal use at site.
5. Props shall be of steel only. The size and verticality shall be approved by the PM. Its spacing shall be as per design it shall be vertical and in correct plumb. Base shall be proper steel plate or timber plank for equal distribution of load.
6. In repeated use, panels shall be clearly marked for using at defined locations.
7. Successive lift shall be tightened with previous lift by fixing foamed strips.
8. In fill pieces and panels shall be well dressed, levelled and jointed with main formwork so as to achieve smooth & even natural finish.
9. Props, Soldiers, Wailers, Shores, Bearers, Clamps, wall & ties etc. shall be at required spacing as per approved design.
10. Props, Shores shall be securely braced with firm bearing.
11. Provide and fix only inserts pockets, to correct line and level and with sufficient rigidity to keep in position while concrete placing is in progress along with vibration.
12. Sloping, brackets, chajjas etc, shall be well secured and firmly restrained.
13. Adequate access and working platform shall be arranged with required safety to avoid reinforcement displacement, damage to shuttering and easy movement of concrete gang.
14. Props and scaffolds are to be erected to correct plumb, line, and level and with required tie. Load carrying of props shall be as per table of manufacturer.
15. Props and scaffolds shall not be loaded more than allowed by the manufacturer.
16. Beams and slabs shall have camber as per structural drawings or as directed by the PM.
17. All angles and corners shall be sharp and well defined, in places where concrete edges are permanently exposed and require no further treatment.
18. Props of steel shall be provided with adequate horizontal and cross bracing above 3,5m ht, Steel props shall be high steel pipes and steel couplers.
19. At the design and erection stage, the following additional points shall be considered and incorporated.
a) Opening for cleaning prior to start of
concreting.
20. Surfaces shall be treated with mould releasing oil or emulsion as approved by the PM prior to reinforcement laying.
G) FOLLOWING POINTS SHALL BE OBSERVED VERY CAREFULLY.
a) Joints of moulds shall be water-light.
b) Props shall be on solid base, in correct plumb, in one straight line, and brazed horizontally and
cross-sectionally.
c) Tie bars in beams, walls and columns shall be at the correct place and fully tight.
d) Wedges shall be fully secured and nailed with head left out for easy removal.
e) All saw dust, dirt, shaving and nailed with head left out shall be removed.
f) Provision shall be made for watching form work while concreting and any other platform needed
for movement of workers without any disturbance to reinforcement.
H) CHECKS BEFORE CONCRETING.
1. All props and struts are in correct plum at right spacing properly tightened up and locked.
2. Formwork is correctly aligned and levelled.
3. Stop ends are properly secured and sealed.
4. Secured ties are properly tightened...
5. Joints are sealed and no possibility of leakage of grouts.
6. Reinforcement has proper covers and required spacers.
7. All forms are cleaned, free from rubbish, tie wires etc.
8. Proper access for concreting and compaction available.
9. Required guard rails, toe boards are provided.
I) TOLERANCE FOR FORM WORK.
Tolerances for RCC buildings
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1
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Variation from
the plumb
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a
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In the lines and
surfaces of columns, piers, walls and in arises 3mm per 2.5 m but not more
than 10mm.
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b
|
For exposed
corner columns and other conspicuous lines,
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In any bay up to
5m maximum
|
5mm
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In 10m or more
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10mm
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2
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Variation from
the level or from the grades indicted on fie drawings
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||
a
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In soffits of
slabs, ceilings, beam and in arises
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In 2.5mm
|
5mm
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In any bay up to
5m maximum
|
8mm
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||
In 10m or
more
|
10mm
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||
b
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For exposed
lintels, sills, parapets, horizontal grooves and other conspicuous lines,
|
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In any bay 5m
maximum
|
5mm
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In 10m or
more
|
8mm
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3
|
Variation of the
linear building lines from established position related position of columns,
walls and partitions.
|
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In any bay up to
5m maximum
|
5mm
|
||
In 10m or
more
|
10mm
|
||
4
|
Variation in the
sizes and location of sleeves, openings in walls and floors 5mm (except in
the case of and for anchor bolts).
|
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5
|
Variation in
cross-sectional dimensions of columns and beams and in the thickness of slabs
and walls – 5mm + 10mm.
|
||
6
|
footings
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||
a
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Variation in
dimension in plan
|
-5mm
+ 50mm
|
|
b
|
Misplacement or
eccentricity
|
2% of footings
width in the direction of misplacement but not more than 50mm
|
|
c
|
Reduction in
thickness
|
5% of specified
thickness subject to a minimum of a 50mm.
|
|
7
|
Variation in
steps
|
Riser
|
Treads
|
In a flight of
stairs
|
3mm
|
5mm
|
|
Consecutive
steps
|
1.5mm
|
3mm
|
|
Tolerances in other concrete structures.
|
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1
|
Variations of
dimensions to individual structure features from established position in plan
|
||
In 5mm
|
5mm
|
||
In 10mm or
more
|
10mm
|
||
2
|
Variations of
dimensions to individual structure features from established positions
|
||
In 20mm or
more
|
25mm
|
||
In buried construction
|
50mm
|
||
3
|
Variation from
plumb, specified batter or from curved Surfaces of all structures
|
||
Up
to
2.5m
|
3mm
|
||
2.5 to
5m
|
8mm
|
||
5m to 10m
|
12mm
|
||
In the buried
construction
|
Twice the above
|
||
4
|
Variation in
cross sectional dimensions of columns, beams, buttresses, piers, and similar
members.
|
(-) 5mm
(+) 10mm
|
|
5
|
Variation in the
thickness of slab, walls, arch section, and similar members.
|
(-) 5mm (+)
10mm.
|
|
6
|
Footings for
columns, pipers, was, buttresses and similar members
|
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Variations of
dimensions in plan
|
(-) 10mm
(+) 50mm
|
||
7
|
Misplacement
or eccentricity
|
2% of footing
width in the direction of misplacement but not more than 50mm
|
|
8
|
Reduction in
thickness
|
5% of specified
thickness subject to a maximum of 50mm
|
|
PASCHAL offers various system solutions for forming square and rectangular concrete columns. The adjustable Modular column formwork by PASCHAL is a steel frame formwork whose elements are assembled according to the so-called windmill principle. With four elements each square and rectangular column the cross-sections can be formed in the adjustment range of 20 cm to 50 cm in increments of 5 cm.
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