PROCEDURE TO CARRYOUT CONCRETEING WORK AT SITE
CODES / SPECIFICATIONS
IS 456, IS 10262 & SP 23
DEPLOYMENT OF LABOR
1 The categorized list for labors is as follows:
2 1Labours
3 Masons
4 Carpenters
5 Carpenter helpers
6 Concrete pump operator
7 Concrete pump helpers
8 Fabricators
As per requirement of the work, labours shall be deployed
accordingly.
REINFORCEMENT STEEL
All reinforcement used in this work shall conform to IS:
1785 with Fy =500N/SQ MM and will be in the form of deformed bars this
reinforcement shall be indicated in the reinforcement details as “T” (For
example T8 @ 150C/C or 4Nos. T12)
CONCRETE
Cement: All cement used for structural purpose shall be 53
grades ordinary Portland cement.
Coarse Aggregate: Coarse Aggregate shall confirm to IS : 383
or 515
Coarse Aggregate: Maximum nominal size of coarse aggregate
shall be 20MM.
Admixtures and other construction chemicals: All such
chemicals shall be approved by the consultants before their use in concrete.
READY MIX CONCRETE
RMC shall be supplied by the Client through different
vendors of grade M 7.5, M15, M40 & M60 and as per approved mix design.
M-15 concrete shall be used for all concrete used as plain
cement concrete under rafts, bases as leveling courses, flooring on grade or
as filling material.
M-40,M-50 & M-60 concrete shall be used for all
structural members.
Temperature of concrete when poured shall not exceed 40˚C
for grades other than M-60 which shall not exceed 25˚C.
WATER
Water shall conform to requirements of IS : 456
Water storage tanks shall be such as to prevent the inclusion of any
deleterious materials.
BINDING WIRE
Binding wire ( GI annealed ) shall be 18 gauges conforming
to IS 280 shall be used.
COVER BLOCKS
Cover blocks shall be of concrete and the thickness of such
cover (exclusive of plaster or other decorative finish) shall be as specified
in drawing. Strength of these cover blocks shall be equal to the strength of
concrete in use. These should be fully cured prior to use in works. The PVC
cover block can be permitted with due approval from Client / Structural
consultant.
SHUTTERING OIL FOR FORM WORK
Form releasing material (oil of good quality) shall be
applied to forms before fixing in position. After removing the form, Form shall
be cleaned properly to maintain good quality of finish.
PVC PIPE FOR WEEP HOLES:
Weep holes shall be provided at5m c/c in both directions for
M7.5 behind retaining wall. 2’ PVC pipe of pressure rating 4Kg/cm² approved
make shall be used.
LIST OF PLANT EQUIPMENT
1 PUMP
2 TOWER CRANE
3 NEEDLE VIBRATOR
4 SURFACE RETARDER SPRAY
5 CONCRETE BUCKET
6 AIR COMPRESSOR
7 HAND BREAKER
LABORATORY EQUIPMENT'S:
Laboratory Equipment at Structural Strengthening, Repairs
& Dismantling Work
Sr. No.
|
Description
|
Specification
|
Unit
|
Quantity
|
1
|
Slump Cone as per IS
|
With Tamping Rod
|
No
|
1
|
2
|
Cube test machine with digital display capacity
|
200 Tons capacity
|
No
|
1
|
3
|
Cube Mould as per
IS: 10086
|
150x150x150mm REGULAR
|
No
|
60-72
|
4
|
Electronic Balance
|
20Kg Accuracy ±1gm
|
No
|
1
|
5
|
Enamel Tray
|
600x450x50mm
|
No
|
2
|
6
|
Enamel Tray
|
450x300x50mm
|
No
|
2
|
7
|
Measuring Beaker
|
500ml
|
No
|
2
|
8
|
Measuring Cylinders
|
500ml
|
No
|
2
|
DEPLOYMENT OF MANPOWER
Following manpower are required for concreting purpose.
Depending upon quantum of work the deployment shall be decided.
PUMP OPERATOR
RIGER AT PUMP
MASON
NEEDLE OPERATORS
MECHANIC
IMPLEMENTATION
Supply of Ready Mix Concrete (RMC):
- The concrete is supplied by the Client through various vendors.
- Transportation of concrete shall be done by a RMC vendor transit mixer.
- Each transit mixer will be accompanied by a batch sheet which will be duly verified by QC Engineer with approved mix design after the slump is found satisfactory as per approved mix design, the contractor shall place concrete into either pump/crane/bucket accordingly depending on the quantity of concrete to be handled, lift of concrete and thickness of concrete.
- No concrete shall be placed without the Client’s approval
- The Contractor shall seek the Client’s / Consultant’s prior approval of the form work and reinforcement being ready for inspection, and the intended time for pour to commence Concrete placement shall not commence until inspection have been carried out outstanding work completed or corrected and approval to proceed given by the Client/ Consultant. All built in conduits, pipes, fittings, guards, block outs, bolts and reinforcement and other fittings shall be in a positions and secured before placing is commenced. Prior to concrete sand mortar shall be applied to horizontal joint mix same as that of concrete.
- Concrete shall be pumped through pump located at convenient location and transferred to location of pour by pipeline. Concrete shall be poured inside forms by connecting bends and 1m long pipe to pipe carrying concrete. Concrete shall be poured in layer of 450mm.
METHOD OF PLACEMENT
- Concrete shall be gently deposited as if practically possible, in its final position to avoid re-handling and shall be so deposited that segregation of aggregates does not occur. In case of deep trenches and footing, it may be done with the help of a chute.
- Concrete on to a sloping surface shall be discharged by providing a chute with a baffle and a drop at its end so that the concrete remains on the slope.
- Concrete shall be placed in a layers not exceeding 450mm deep in deep beams and placed to the full depth in slabs and small beams. When a layer is not completely placed in one operation, it shall be terminated in a vertical bulkhead. Each layer shall be placed and compacted before the preceding layer has taken its initial set and in a manner that will entirely break-up and prevent any construction joint forming between the layers. All placements shall be made in one continuous operation between construction joints or approved by the Consultant. Construction joints shall be properly treated.
- For concreting at greater than 1.5m height, suitable tremie shall be placed.
COMPACTION OF CONCRETE
- Concrete shall be thoroughly compacted as depositing proceeds by means of suitable vibrators. The vibrators shall maintain the entire concrete under treatment in an adequate state of agitation and shall continue during the whole duration of concrete placement. Care shall be taken not to over vibrate the concrete. While withdrawing vibrator needles, no holes should be visible in concreting. Compaction shall be completed before the initial setting time. Successive vibrations shall not disturb concrete already set. If required surface vibrations also will be used.
- It shall be ensured that the needle vibrators are not applied on reinforcement, which may destroy the bond between concrete and reinforcement.
- When electric vibrators are in use, the standby vibrators must always be available at the concreting point. Atleast two (2) vibrators shall be used, and an adequate number of standby vibrators shall be available on site in case of breakdowns. Workmen skilled in their use shall operate vibrators.
CONSTRUCTION JOINTS
Following are the places where the joints shall be treated as mentioned
- In large pours, it is practically not possible to carry on concreting continuously and hence construction joints shall be provided.
- All construction joints – their position and detailed arrangement shall be approved by the consultant before concreting.
- All vertical construction joints shall be formed with a vertical stopping board against which proper vibrating is possible.
- Proper keys shall be provided to form horizontal construction joints.
- Before resuming work at any construction joint where concrete has not yet fully hardened. All laitance shall be removed thoroughly. Before commencement of concreting, adjacent concrete stopper and surfaces shall be chipped and roughened to expose aggregate & cleaned. All loose concrete shall be removed by chipping.
- Location and arrangement of shrinkage strip shall be marked on the drawing and approval shall be obtained from the consultants before proceeding to execute the work the casting of the part of the slabs.
- Maximum dimension of rectangular wall panel cast in one pour shall not exceed length specified by consultant for retaining wall & 16m for raft the minimum time between adjacent pours shall not be less than 48 hours.
- Maximum plan dimension of a rectangular wall panel of the floor slab cast in one pour shall be as specified by the consultant.
EXPANSION JOINTS
Expansion joint shall be formed and located as detailed in
the approved drawing.
CURING
- Curing of concrete is an extremely important aspect of the work. Proper arrangement shall be done so that the concrete is cured to the complete satisfaction of the Client. After concrete has begun to harden (i.e. about 1 to 2 hours after laying), it shall be protected from quick drying with moist or damped Hessian cloth. After 12 hours of laying of the concrete, the surface shall be cured by flooding with water for period of 14 days to keep it moist. Date of casting will be marked on every pour.
- If in the opinion of the Client curing is inadequate, we shall use approved curing compounds.
Shrinkage Cracks.
Concreting shall be avoided in very hot weather. If
necessary exposed concrete surfaces shall be covered with damped hessian within
2-hours of placing of concrete.
To achieve good results the concrete shall be immediately
covered a plastic sheet/ wet hessian cloth and not allowed any direct wind
contact
FINISHING
- Concrete shall be finished keeping in mind the next operation to be carried out over the surface.
- For guidance the following points shall be noted but the Engineer shall be consulted prior to start of concreting and his decision in this regards shall be final.
- All slabs shall be toweled even and smooth with a wooden float.
- Laitance shall be removed from the surface of the finished concrete.
- Surfaces that will receive plaster shall be roughened immediately.
- Surface that will be in contact with any masonry work shall be roughened immediately.
- The surfaces that will receive mosaic floor or IPS or any other type of tile work shall be roughened while it is green. Every care shall be taken not to disturb the freshly laid concrete.
- Workshop floor shall be broom finished transverse to the direction of the slope.
- All the construction joints in the retaining walls, raft, junctions of column footings and raft, junctions of retaining wall foundations and raft/column footings and floor slabs up to plinth level/ground floor level/podium level shall be grouted with waterproof Cementations grout to ensure leak proof joints by specialized agency.
- Particular attention should be given to the surface level tolerance for all floors.
This
being ± 6mm.
INSPECTIONS AND CORRECTIVE MEASURES
On removal of form work, the surface shall be examined by the
Client. Till such time, no remedial measures shall be carried out by the
contractor. All patching, rectification or chipping shall be done only on the
Client’s instruction.
Cracks observed shall be brought to the notice of client who
shall examine them. It shall be kept under observation and a record shall be
maintained for period of 45 days. It shall be shown to the client and the
following procedure shall be followed:
Cracks not developing further and in the opinion of Consultant,
detrimental to the strength of the concrete shall be grouted with non-shrinking
cement slurry, cementations grout or as directed by the Consultant.
Cracks developing further and in the opinion of the
structural Engineer, detrimental to the strength
Based on the results of the test, on consultation with the
Design Consultant shall order remedial measures.
The decision of the Consultant in this matter shall be final
and binding on all parties.
REPAIR METHOD
Following compounds used for repair works
POLYALK EP as POLYMER MODIFIED CEMENT MORTAR (PMCM)
Take 1 kg. POLYALK EP, 5 kg. Fresh Cement, 15 kg. Quartz
sand (Graded). (Polymer: Cement Quartz sand ratio is 1:5:15).
This is globally
recommended composition. However, the proportion can be modified based on
Consultant’s recommendations.
First dry mix the cement and graded sand in a mixer.
Mix POLYALK EP with the premixed cement sand in the mixer.
Mix it for at least 3 minutes. A mechanical mixer with a
specially designed stirrer may be conveniently used.
Add requisite quantity of water to attain dough like
consistency so that it can be hand packed. The mortar is now ready for use.
TESTING / ACCEPTANCE
As per IS 516, IS 456 & SP 23
QUANTUM OF CUBES AND TESTING:
- The minimum frequency of cube casting shall be as follows. Each sample shall consist of 6 cubes.
Concrete Quantity
|
Number of Sample
|
Upto 5 cu. m in a day
|
1
|
6 cu. m to 15 cu. m
|
2
|
16cu. m to 30 cu. m
|
3
|
31 cu. m to 50. cu. m
|
4
|
More than 50 cu. m
|
4 + one additional per each 50 cu. m or part thereof
|
- Cubes would be tested for compressive strength of 28 days, as per above criteria. Additional samples shall be cast and tested for accelerated curing, 3 days, 5 days, 7 days as required.
- In addition, samples shall be taken whenever any of the materials or the proportions of the mix are changed or whenever directed by the Engineer.
- The samples shall be taken and the test cubes cured in accordance with the requirements of IS-516. Three shall be tested after 7 days and remaining thereafter 28 days in a laboratory approved by the Consultant.
METHODOLOGY OF FOR CLOSING OF TIE-ROD HOLES IN WALL
- As per approved shuttering design tie-rods are provided through PVC conduct / PVC cones while shuttering of Retaining.
- After de-shuttering of wall these holes of tie-rod in concrete need to be closed.
Preparation
- Along with de-shuttering of wall tie-rods are removed.
- PVC conduct / PVC cones left out in concrete used to fix tie-rods are removed.
Material used for closing holes:
- Polymer treatment material which is generally used
Procedure
- Cut the PVC pipe equivalent to the concrete face.
- Apply polymer material in the hole and match it with the existing concrete face.
PLUM CONCRETE
- Before Proceeding with plum concrete the raft surface to be cleaned properly by removing left out concrete, any loose material on raft & footing. Pour area shall be marked.
- The shuttering like concrete stopper shall be placed in position with required supporting arrangement.
Stacking
- The required quantity of plum of size from150 to 300mm shall be stacked near the pour area.
Shifting
- The shifting of plum shall be done manually with the help of wheel barrows & mechanical means by tough rider, or tower crane with bucket arrangement.
- All plums shall be hard, durable and clean and shall not have sharp corners.
Laying of Plum Concrete
- During concreting the first layer of concrete of the specified mix (M7.5) shall be laid to a thickness of at least 350mm with the help of concrete pump.
- The plums shall then be laid while the top portion of this concrete is still green but sufficiently stiff to prevent complete submergence of the plum under their own weight.
- These plums shall be about half embedded in the concrete and remaining part exposed so as to form a key with the next layer of concrete. Successive layers of concrete and plum shall be laid over and above this layer in proportion 70% concrete and 30% plum and this procedure shall be continued till necessary level is achieved.
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