Shuttering / moulds:
In any concrete shuttering is very much essential which consists of the surface which is directly coming under contact of concrete which holds the concrete in desired shape and alignment which may be of Mud shuttering , steel plates, ply boards , waffle moulds of fiber materials , MS sheets etc. Supported by wooden runners, MS angles, and Acrow spans placed with vertical supporting of casolona bellies runner’s, jacks, Coupler blocks etc. The shuttering will be designed considering the thickness and weight of concrete slab / column beam etc, structures span to be supported working load mode of placement.
Considering all the aspects the mould will be created as per drawings and design aspects care will be taken to avoid slurry leakages, any sort of openings in the mould / to with stand the load above / any dynamic forces at the time of placement / perfect adherence with old concrete structures will be taken in to accounts and also packing or sealing the board joint cavities with cello tape form strip with proper adhesives. Further the proper back up supporting of grid works with runners are column box, back supporting etc considering the design aspects in a direction of keeping the stability of the mould at the time of concrete.
Let us discuss in depth how the mould will be updated
Design :- desired load will be considered in case of slab keeping 110mm ( C ) /150mm ( B ) /200mm ( C ) slab where plate will be the surface which will contact of concrete which also designed load of 250 to 400 Kg load per Running meters with a span between supporting backing runners of 500mm /400mm and 300mm respectively will be of ply of 10mm for 110mm thick and 12mm ply boards for 150mm and 200mm . Fallowed with Acrow / I section / box section support designed for a working load of 2.5Mt to 3Mt per No it will be recommended with 900mm, 750mm and 600mm spacing for C B A loading. However desired Level is the concern on present day as the ceiling final finish now with 4mm Max thickness which needs to be updated with proper check.
Now the load will be transferred Acrow span to end which needs to be of study members to take the half slab loads in general which will help in maintaining rigidity of mould by using Key runners of 3”X 4” / 4’X6” holding all members backed with Jacks / Coupler Blocks / casolona bully with base plate or U clamp and nailed for perfection. now the total load needs to be shifted from top to down bellow supporting slab or ground which considered to be Jacks with 700Kg to 1000Kg based on the thickness of pipes / Coupler block for 2000Kg for one side base plate and one side U clamp and 1500 Kg with both side U clamp however Casolona bully is out dated in our sites still 250 to 400 Kg based on Diameter which wares from 2.5” to 4” with proper base support of 80% + with a single wooden packing with perfect level.
As a safe practice, the cross bracings, diagonal bracings to take care of any jerks, impacts at the time of concrete. Considering the strength attain by the down below structures and age of the structures the props of 50% & 25% of the normal concreting in the moulds soon after the retention period of the shuttering system de-shuttering will be taken care considering the strength attained by the concrete. Retention period of the moulds will be mainly based on span of the supports of the RCC structures that will be very well defined in the detailed specification or in the relevant IS. Which defers between 7 days up 3-4Mts above, 4-5 Mts will be 14 days and 21 days above 5Mts spanning.
The total self load of and any slab load planned to be shifted not more than 300mm will be considered for design aspects which will be between 1Mt – 2.5Mt per RM in general which can be considered in base and sides base off course needs to be with 10mm/ 12mm Ply supported with cross runners of suitable size 300mm, 400mm, 500mm based on load which loaded on Jacks and base plates.
Beam and columns sides needs to be with adequate back supporting depending on heights I.e. 800mm Max for 300mm height , 600mm for 450mm , 500mm for 600 mm height and 300mm for above heights and middle runners backing with Max of 450mm C/C in case of 900 mm above with proper supporting from sides.
For long use more repetitions of the said materials, it is mandatory to use proper shuttering oil to avoid the water entry to the ply boards easy de-shuttering and to achieve a good finish in RCC structures. Greasing will be done for the jacks and screws in the jacks to have a smooth usage clamping will be done as per the manufactures specifications and design concepts. Care should be taken while using Acrow spans by ensuring the central insertions as per the manufactures specifications; usage of proper Acrow spans for proper span of the supporting will ensure the stability of molding system. Apart from all these points it is very much essential to know the sequence of pouring to take extra precautionary measures to see that any sort of eventualities will not occur.
It is very essential to take proper maintenance of the ply boards by filling the cavities of Tie-rods /gugu-rods / shikanja or tie rods as well as the damages occurred at the time of concrete or de-shuttering activities by filling the wax, wooden plugs or any glue adhesives to ensure more repetition.
Removing with back propping without keeping the slab on hanging is the technique which needs to be well managed by adequate temp supports for this shuttering needs to be planned for specific ply board placement to minimize the resources management for Ex maintaining 1200mm ply and 300mm py alternative in crosswise of spanning supporting 300mm ply and removing all / maintaining add supports in alternative play and updating with back-propping etc witch needs to be with proper supervision.
Special type of shuttering:
Other than our conventional shuttering using ply, Acrow spans jacks and normal runners we are having modern systems like Doca, this as weight will be more where Crain / tower Crain are available it can be used for structures with larger dimensions which also minimize no of pours still becomes economical considering reduction in project period.
Now, pre fabricated structural members of fixed sizes, are available in industry which will be lifted by hydraulic jacks and supported by verticals with try pots, supposed to be most efficient, because of increase of repetitions. Man handling is being least because de-shuttering will also by using hydraulic jacks. This requires professional training for handling the system, perfect numbering to avoid miss matches in ply also usage of standard shuttering oil and maintenance of ply after successive repetition is mandatory. In beginning it seems to be not viable but in due course it is more economical, time saving.
Double height / Malty height shuttering which will be having a rigid platform at 3mts with proper brazing and further updated in normal shuttering however all the above design in general for 3 Mts which can be updated single Brazing between 3-5Mts can be Double brazing. Load considerations in this case can be limited to 80% for Jacks and Coupler blocks and bully stated above.
Slip form shuttering which will be used in Circular concrete members which will be having a grid platform moves with designed speed in verticality with centralized jack / pulley blocks with proper motors to pull up during the time all re baring I P members electrical installations needs to be updated
Acceptance of Materials: Conforming to IS-786 for chemical as well as physical test. In site the soon the material arrive the respective QC, in charge must take the assistance of the bar bender fitters to ensure about temper of the material to ascertain the quality of the material against localized resting and stripping in between. Bending and re-bending test can be done by the fitter in site to asset the range of quality after getting the guarantee that the materials can be unloaded. Subsequently the three samples of known length can be taken and sent to laboratories where it will go under physical and chemical analysis test. In physical test, specific weight and proof stress will going to be carried out and checked for the respective results, for chemical analysis carbon, phosphorous, sulphur. Contents will also be checked for 0.32%, 0.065% and 0.065% respectively as the maximum criteria’s. Samples, which are not fulfilling the requirement, will be rejected and intimated to suppliers and take back to stock at the earliest.
Stacking of the materials: The materials received will be stacked making raised/bifurcated from the ground to see that water stagnation will come in contact with the rivers; it is also necessary to stack these materials preferably in protected area to avoid rust. Rods are to be stacked diameter wise separately to avoid confusion in identification and suitable boards with bin cards are tagged it is very much essential to see that cut rods which may going to be termed as scrap is also to be stacked properly diameter wise to see that this can be utilized whenever lower sides dimensional requirements exists which will give a very good reduction in scrap. Logical planning and calculation of clubbing the same diameter rods at the time of cutting will definitely give a very good saving which will direct towards zero scrap age.
It is very much mandatory to take care of the positioning of the bars for updating the design criteria, the cover thickness as desired by the drawings should be maintained to achieve more effectiveness. Binding of rebar should be with the specific binding wire mentioned: must be ascertained. It is very much essential to see that place of binding should be free from muck, fungi and other foreign elements. It is always mandatory to keep lap lengths, development lengths any protruding of rods from the structure for further construction activities as desired by the drawing without fail, it is also mandatory to get the four cards checked and duly signed by the competitive authority before the start of any concrete.
Now in industry spicing is being started in major projects which is economical in higher diameter technically also much superior then normal lapping, where quality binding of rods kinking at end is doubtable in most of time. In spicing also quality of threading, protecting the threads till tightening and proper tightening will play major role as well as quality is concerns. In one of projects for 2000MT usage Iron rings to hold rod bundles amounted to 10 Mt which is 5% of rod weight. If we use spicing as a hole for rod more than 20mm diameter we can achieve saving not less than 15 % as a hole by avoiding lapses which also amounts to global resources conservation.
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