Formwork is defined as temporary structure whose purpose is to provide support and containment for fresh concrete until it can support itself. It moulds the concrete to the desired shape and size and controls its position and alignment. The development of formworks is parallel with the growth of concrete construction throughout the 20th century. The advancement of technology, increase of population and the space limitation lead the way to construct high-rise buildings. But the task was not very easy at the beginning but now the man made the task easy by inventing new machinery and new techniques. The most important factor in terms of cost, quality and speed in a high-rise building construction project is the type of the formwork used in the project. The first formwork type to be used is the conventional type formwork where the timber planks were supported on timber columns. With the advancement of technology it developed gradually and people used ply wood sheets instead of timber planks and steel pipes with jacks were used to support the ply wood. Then people invented small units of formworks and connect the repeating units in the construction. The larger units were invented like formworks for slab panels, formworks for columns, beams etc. when the same elements are repeating. Then finally the whole system of formwork is made and initially the material used to it was steel and it was very heavy. Then the aim was to reduce the weight of the system and the materials for formwork have extended to aluminium, plastic, fibre glass etc.
Aluminium formwork system provides aluminium formwork for RCC load bearing or RCC framed multi-storied buildings and enables the walls and slabs to be poured in same operation. These increases efficiency and also produces an extraordinarily strong structure with excellent concrete finish. Due to the fine tolerance achieved in the machined metal formwork components, consistent concrete shapes and finishes are obtained floor after floor. This allows plumbing and electrical fittings to be prefabricated with the certain knowledge that there will be an exact fit when assembled. As described by the manufacturers a low-cost system for housing using aluminium formwork. Aluminium formwork system is construction system for forming cast in place concrete structure of building. It is also a system for scheduling and controlling the work of other construction trends such as steel reinforcement, concrete placement and mechanical and electrical conduits. This type of construction requires a restructuring of the entire conventional construction process to enable interaction between the design phase and production planning in order to improve and speed up the construction. The speed of construction by this system will surpass speed of most of the other construction method.
2. INNOVATION IN CONSTRUCTION
The traditional mode of construction for individual houses comprising load bearing walls with an appropriate roof above or reinforced concrete (RC) framed structure construction with infill masonry walls would be totally inadequate for mass housing construction industry in view of the rapid rate of construction. Further, such constructions are prone to poor quality control even in case of contractors with substantial resources and experience.
“For undertaking mass housing works, it is necessary to have innovative technologies which are capable of fast rate construction and are able to deliver good quality and durable structure in cost effective manner”.
Several systems are adopted at different places in the world; eventually the systems which are reasonably economical and easy for operation with skilled labor are useful in India. Certain systems are in vogue and more and more contractors are trying to bring in new technologies. These are essentially based on the basis of mode of construction, namely, pre-cast construction or in-situ construction.
2.1 Cast-in-Situ Construction
Pre-cast and cast-in-situ are techniques that are used for quick construction. Pre-cast includes the wall-panel units and slab units directly added to building structure. The use of aluminium also evolved as one of the technique for quick construction by use of aluminium and steel (tunnel) formwork. As a matter of fact the cost of the formwork may be up to 25% of cost of the structure in building work, and even higher in bridges, it is thus essential that the forms are properly designed to effect economy without sacrificing strength and efficiency.
Certain patented systems based on imported technologies such as “Mascon System” (Canada), “Mivan System” (Malaysia) have come on the Indian scene in recent years. In these systems traditional column and beam construction is eliminated and instead walls and slabs are cast in one operation at site by use of specially designed, easy to handle (with minimum labor and without use of any equipment) light weight pre-engineered aluminium forms. Rapid construction of multiple units of a repetitive type can be achieved with a sort of assembly line production by deployment of a few semi-skilled labors.
The entire operation essentially comprises fitting and erecting the portion of shuttering as already determined (the optimization in use is determined by appropriate planning) and then carrying out concreting of the walls and slabs. Props are so designed that they stay in position while de-shuttering of slabs and/or takes place. The dimensional accuracy of the formwork is of high order. Therefore any possibility of errors does not rise.
2.2 “3-S” SYSTEM OF PRECAST CONSTRUCTION
An engineered system of building construction, namely “3-S” system was developed by B.G.SHIRKE CONSTRUCTION TECH LTD., for achieving, speed, strength, safety and economy in construction practices. The system involves structural elements such as pre-cast hollow column shells pre-cast concrete beams, light weighed reinforced cellular autoclaved concrete slabs for floor and roofs constituting the basic structural formwork. The “3-S” system involves activities for construction of building such as:
I. Cast in-situ sub-structure including foundations, stem columns, plinth beams, plinth masonry.
II. Erection of partial pre-cast components, jointing of these components using cast in-situ concrete with appropriate reinforcement.
III. Lying of reinforced cast in-situ screed over slab panels, construction of panels, construction of walling, flooring, plastering, water proofing etc.
Achieving the “3-S” system in the MIVAN formwork is quite easy. MIVAN formwork has got the unsurpassed speed of construction due to saving time for required time in masonry and plastering. The strength of raw aluminium is very less but when alloyed with other materials prove to be strong enough to use as a formwork. To ensure safety in the site, an integrated safety/ working platform is developed which ensures labor safety during erection and striking of the formwork. Economy is also one of the main factors of any system. The MIVAN formwork proves to cost efficient as it can be used efficiently for 250 times.
When concrete is placed, it is in plastic state. It requires to be supported by temporary supports and castings of desired shape till it becomes sufficiently strong to support its own weight. This temporary casing is known as the formwork or forms or shuttering. The term moulds is sometimes used to indicate formwork of relatively small units such as lintels, cornices etc.
3.1 Definition of formwork
“Forms or moulds or shutters are the receptacles in which concrete is placed, so that it will have desired shape or outline when hardened. Once concrete develops the adequate strength to support its own weight they can be taken out”.
“Formwork is the term given to either temporary or permanent moulds into which concrete or similar materials are poured”.
3.2 Requirements of a good formwork
The essential requirements of formwork or shuttering are: -
a) It should be strong enough to take the dead and live loads during construction.
b) The joints in the formwork should be rigid so that the bulging, twisting, or sagging due to dead and live load is as small as possible. Excessive deformation may disfigure the surface of concrete.
c) The construction lines in the formwork should be true and the surface plane so that the cost finishing the surface of concrete on removing the shuttering is the least.
d) The formwork should be easily removable without damage to itself so that it could be used repeatedly.
3.3 Types of Formwork
The material most commonly being used to date is timber. However, due to the depleting forest reserves and increasing cost of timber the use of alternate materials such as plywood and steel has become prominent. More recently, materials such as plastics and fiberglass are also being used for pre-fabricating formwork. The type of material to be used depends on the nature of construction as well as availability and cost of material. The constraints on the project such as overall cost, time of completion also play a major role in the use of a Particular material for formwork.
a) TIMBER FORMWORK
Timber is required for practically all jobs of formwork. The timber bring used for formwork must satisfy the following requirements. It should be durable and treatable. It should have sufficient strength characteristics. It should be light weight and well seasoned without warping. It should hold nails well. It is economical for small construction jobs. It is design flexible and easy to erect. It has good thermal insulation which makes it useful to be used in colder Regions. It can easily be made into any shape or size. And it is easy for transporting purpose for in between sites.
Fig 3.1Timber Formwork
b) STEEL FORMWORK
Mostly used in large construction projects or in situations where large number of re-uses of the same shuttering is possible. It is Suitable for circular or curved shaped structures such as tanks, columns, chimneys etc. and also used for structures like sewer tunnel and retaining wall. Strong, durable & have longer life. Reuses can be assumed to vary from 100 to 120 wares timber varies from 10 to 12.Steel can be installed & dismantled with greater ease & speed resulting in saving in labour cost. Excellent quality of exposed concrete surface obtained. No danger of formwork absorbing water from the concrete and minimizing honeycombing.
Fig 3.2 Steel Formwork
c) PLASTICS FORMWORK
These forms have become increasingly popular for casting unique shapes and patterns being designed in concrete because of the excellent finish obtained requiring minimum or no surface treatment and repairs. Different types of plastic forms are available like glass reinforced plastic, fiber reinforced plastic and thermoplastics etc. The material allows greater freedom of design. Unusual textures and designs can be molded into the form. It allows the contractor to pour structural and finished concrete simultaneously. Because sections can be joined on the job site in such a way so as to eliminate joints, there is no size limitation. If carefully handled, a number of reuses are possible making it highly& Economical. It is lightweight and easily stripped. The disadvantage of using plastic forms is that it does not lend itself to field fabrication hence, the design and planning of this form must be carefully carried out. Also care must take not to damage the plastic by the heat applied for accelerated curing of the concrete. Trough and waffle units in fiberglass are used in construction of large floor areas and multistoried office buildings.
Fig 3.3 Plastic Formwork
d) ALUMINIUM FORMWORK
Forms made from aluminum are in many respects similar to those made of steel. However, because of their lower density, aluminum forms are lighter than steel forms, and this is their primary advantage when compared to steel. As the strength of aluminum in handling, tension and compression is less than the strength of steel, it is necessary to use large sections. The formwork turns out to be economical if large numbers of reuses are made in construction. The major disadvantage of aluminum forms is that no changes can be made once the formwork is fabricated.
Fig 3.4 Aluminium Formwork
3.4 Loads acting on Formwork
In Construction, the formwork has to bear, besides its own weight, the weight of wet
concrete, the live load due to labor, and the impact due to pouring concrete and workmen on it. The vibration caused due to vibrators used to compact the concrete should also be taken care off. Thus, the design of the formwork is an essential part during the construction of the building.
concrete, the live load due to labor, and the impact due to pouring concrete and workmen on it. The vibration caused due to vibrators used to compact the concrete should also be taken care off. Thus, the design of the formwork is an essential part during the construction of the building.
For the design of planks and joists in bending & shear, a live load including the impact may be taken as 370kg/m². It is however, usual to work with a small factor of safety in the design of formwork. The surfaces of formwork should be dressed in such a manner that after deflection due to weight of concrete and reinforcement, the surface remains horizontal, or as desired by the designer. The sheathing with full live load of 370 kg/m² should not deflect more than 0.25 cm and the joists with 200kg/m² of live load should not deflect more than 0.25cm.
In the design of formwork for columns or walls, the hydrostatic pressure of the concrete should be taken into account. This pressure depends upon the quantity of water in the concrete, rate of pouring and the temperature.
The hydrostatic pressure of the concrete increases with the following cases:-
· Increase in quantity of water in the mix.
· The smaller size of the aggregate
· The lower temperature.
· The higher rate of pouring concrete
· The smaller size of the aggregate
· The lower temperature.
· The higher rate of pouring concrete
If the concrete is poured in layers at an interval such that concrete has time to set, there will be very little chance of bulging. Aluminium as usual is not a very strong material. So the basic elements of the formwork system are the panel which is a framework of extruded aluminium sections welded to an aluminium sheet. It consists of high strength special aluminium components. This produces a light weight panel with an excellent stiffness-to-weight ratio, yielding minimal deflections when subjected to the load of weight concrete. The panels are manufactured in standard sizes with nonstandard elements produced to the required size and size to suit the project requirements.
4. MIVAN: - A Versatile Formwork
The system of aluminum forms (MIVAN) has been used widely in the construction of residential units and mass housing projects. It is fast, simple, adaptable and cost – effective. It produces total quality work which requires minimum maintenance and when durability is the prime consideration. This system is most suitable for Indian condition as a tailor–made aluminum formwork for cast–in–situ fully concrete structure.
Mivan is basically an aluminium formwork system developed by one of the construction company from Europe. In 1990, the Mivan Company Ltd from Malaysia started the manufacturing of such formwork systems. Now a days more than 30,000 sq m of formwork used in the world are under their operation. In Mumbai, India there are number of buildings constructed with the help of the above system which has been proved to be very economical and satisfactory for Indian Construction Environment.
The technology has been used extensively in other countries such as Europe, Gulf Countries, Asia and all other parts of the world. MIVAN technology is suitable for constructing large number of houses within short time using room size forms to construct walls and slabs in one continuous pour on concrete. Early removal of forms can be achieved by hot air curing / curing compounds. This facilitates fast construction, say two flats per day. All the activities are planned in assembly line manner and hence result into more accurate, well – controlled and high quality production at optimum cost and in shortest possible time.
In this system of formwork construction, cast – in – situ concrete wall and floor slabs cast monolithic provides the structural system in one continuous pour. Large room sized forms for walls and floors slabs are erected at site. These forms are made strong and sturdy, fabricated with accuracy and easy to handle. They afford large number of repetitions (around 250). The concrete is produced in RMC batching plants under strict quality control and convey it to site with transit mixers.
The frames for windows and door as well as ducts for services are placed in the form before concreting. Staircase flights, facade panels, chajjas and jails etc. and other pre-fabricated items are also integrated into the structure. This proves to be a major advantage as compared to other modern construction techniques.
The method of construction adopted is no difference except for that the sub – structure is constructed using conventional techniques. The super–structure is constructed using MIVAN techniques. The integrated use the technology results in a durable structure.
4.2 Modular Formwork
The formwork system is precisely-engineered system fabricated in aluminium. Using this system, all the elements of a building namely, load bearing walls, columns, beams, floor slabs, stairs, balconies etc can be constructed with cast in place concrete. The resulting structure has a good quality surface finish and accurate dimensional tolerances. Further, the construction speed is high and the work can be done in a cost effective manner.
The modular nature of the formwork system allows easy fixing and removal of formwork and the construction can proceed speedily with very little deviation in dimensional tolerances. Further, the system is quite flexible and can be easily adapted for any variations in the layout.
The availability of concrete from ready mix concrete facility has augured well for the use of this work system. However, the proliferation of RMC facilities in the cities in India and the willingness to use mechanized means of transport and placing of concrete, the use of aluminium formwork system has received a boost. The quality of the resulting concrete is found to be superior.
Structurally speaking, the adoption of the closed box system using monolithic concrete construction has been found to be the most efficient alternatives. The stresses in both the concrete and steel are observed to be much lower even when horizontal forces due to wind or earthquake are taken into consideration.
The formwork system can be used for construction for all types of concrete systems, that is, for a framed structure involving column beam –slab elements or for box-type structure involving slab-walls combination.
4.3 FORMWORK – COMPONENTS
The basic element of the formwork is the panel, which is an extruded aluminium rail section, welded to an aluminium sheet. This produces a lightweight panel with an excellent stiffness to weight ratio, yielding minimal deflection under concrete loading. Panels are manufactured in the size and shape to suit the requirements of specific projects. The panels are made from high strength aluminium alloy with a 4 mm thick skin plate and 6mm thick ribbing behind to stiffen the panels.
The panels are manufactured in MIVAN’S dedicated factories in Europe and South East Asia. Once they are assembled they are subjected to a trial erection in order to eliminate any dimensional or on site problems.
All the formwork components are received at the site whining three months after they are ordered. Following are the components that are regularly used in the construction.
4.3.1 WALL COMPONENTS
1) Wall Panel: - It forms the face of the wall. It is an Aluminium sheet properly cut to fit the exact size of the wall
FIG 4.1 WALL PANEL
2) Rocker: - It is a supporting component of wall. It is L-shaped panel having allotment holes for stub pin
FIG 4.2 ROCKER
3) Kicker: - It forms the wall face at the top of the panels and acts as a ledge to support.
FIG 4.3: KICKER
4) Stub Pin: - It helps in joining two wall panels. It helps in joining two joints
FIG 4.4 STUB PIN
4.3.2 BEAM COMPONENTS:
1) Beam Side Panel: - It forms the side of the beams. It is a rectangular structure and is cut according to the size of the beam
FIG 4.5 BEAM SIDE PANEL
2) Prop Head for Soffit Beam: - It forms the soffit beam. It is a V-shaped head for easy dislodging of the formwork.
FIG 4.6 PROP HEAD FOR SOFFIT BEAM.
3) Beam Soffit Panel: - It supports the soffit beam. It is a plain rectangular structure of aluminium.
FIG 4.7 BEAM SOFFIT-PANEL
4) Beam Soffit Bulkhead: - It is the bulkhead for beam. It carries most of the bulk load.
FIG 4.8 BEAM SOFFIT BULKHEAD
4.3.3 DECK COMPONENT
1) Deck Panel: - It forms the horizontal surface for casting of slabs. It is built for proper safety of workers.
FIG 4.9: - DECK PANEL
2) Deck Prop: - It forms a V-shaped prop head. It supports the deck and bears the load coming on the deck panel.
FIG 4.10 DECK PROP
3) Prop Length: - It is the length of the prop. It depends upon the length of the slab.
FIG 4.11 DECK PROP LENGTH
4) Deck Mid – Beam: - It supports the middle portion of the beam. It holds the concrete.
FIG 4.12 DECK MID-BEAM
5) Soffit Length: - It provides support to the edge of the deck panels at their perimeter of the room.
FIG 4.13 SOFFIT LENGTH
6) Deck Beam Bar: - It is the deck for the beam. This component supports the deck and beam.
FIG 4.14 DECK BEAM BAR
4.3.4 OTHER COMPONENTS
1) Internal Soffit Corner: - It forms the vertical internal corner between the walls and the beams, slabs, and the horizontal internal cornice between the walls and the beam slabs and the beam soffit.
FIG 4.15 INTERNAL SOFFIT CORNER
2) External Soffit Corner: - It forms the external corner between the components
FIG 4.16 EXTERNAL SOFFIT CORNER
3) External Corner: - It forms the external corner of the formwork system.
FIG 4.17 EXTENAL CORNER
4) Internal Corner: - It connects two pieces of vertical formwork pieces at their exterior intersections.
FIG 4.18 INTERNAL CORNERS
4.4 CONSTRUCTION ACTIVITIES WITH MIVAN FORMWORK
The construction activities are divided as pre – concrete activities, during concreting and post – concrete activities. They are as follows:
4.4.1 PRE – CONCRETE ACTIVITIES:
a) Receipt of Equipment on Site – The equipments is received in the site as ordered.
b) Level Surveys – Level checking are made to maintain horizontal level check.
c) Setting Out – The setting out of the formwork is done.
d) Control / Correction of Deviation – Deviation or any correction are carried out.
e) Erect Formwork – The formwork is erected on site.
f) Erect Deck Formwork – Deck is erected for labours to work.
g) Setting Kickers – kickers are provided over the beam.
After the above activities have been completed it is necessary to check the following.
i. All formwork should be cleaned and coated with approved realize agent.
ii. Ensure wall formwork is erected to the setting out lines.
iii. Check all openings are of correct dimensions, not twist.
iv. Check all horizontal formwork (deck soffit, and beam soffit etc.) in level.
v. Ensure deck and beam props are vertical and there is vertical movement in the prop lengths.
vi. Check wall ties, pins and wedges are all in position and secure.
vii. Any surplus material or items to be cleared from the area to be cast.
viii. Ensure working platform brackets are securely fastened to the concrete.
Fig 4.19 Fixing Mivan Plates
4.4.2 ON CONCRETE ACTIVITIES:
At least two operatives should be on standby during concreting for checking pins, wedges and wall ties as the pour is in progress. Pins, wedges or wall ties missing could lead to a movement of the formwork and possibility of the formwork being damaged. This – affected area will then required remedial work after striking of the formwork. Things to look for during concreting:
i. Dislodging of pins / wedges due to vibration.
ii. Beam / deck props adjacent to drop areas slipping due to vibration.
iii. Ensure all bracing at special areas slipping due to vibration.
iv. Overspill of concrete at window opening etc.
Fig 4.20 Concreting Work of Column, Beam, Slab
4.4.3 POST – CONCRETE ACTIVITIES:
i) Strike Wall Form- It is required to strike down the wall form.
ii) Strike Deck Form- The deck form is then removed.
iii) Clean, Transport and stack formwork
iv) Strike Kicker Formwork – The kicker are removed.
v) Strike wall – Mounted on a Working Platform the wall are fitted on next floor.
vi) Erect Wall – Mount Working Platform and the wall is erected.
Normally all formwork can be struck after 12 hours. The post – concreting activities includes:
All components should be cleaned with scrapers and wire brushes as soon as they are struck. Wire brush is to be used on side rails only. The longer cleaning is delayed, the more difficult the task will be. It is usually best to clean panels in the area where they are struck.
There are basic three methods recommended when transporting to the next floor:
i. The heaviest and the longest, which is a full height wall panel, can be carried up the nearest stairway.
ii. Passes through void areas.
iii. Rose through slots specially formed in the floor slab for this purpose. Once they have served their purpose they are closed by casting in concrete filter
Once cleaned and transported to the next point of erection, panels should be stacked at right place and in right order. Proper stacking is a clean sign of a wall – managed operation greatly aids the next sequence of erection as well as prevents clutters and impend other activities
Fig 4.21: - Erection of Platform
Fig 4.22:- Striking of formwork
Fig 4.23: - Positioning of Platform
Fig 4.24: - Removal of kicker
4.5 SPEED OF CONSTRUCTION
4.5.1 Work cycle
MIVAN is a system for scheduling & controlling the work of other connected construction trades such as steel reinforcement, concrete placements & electrical inserts. The work at site hence follows a particular sequence. The work cycle begins with the deshuttering of the panels. It takes about 12-15hrs. It is followed by positioning of the brackets & platforms on the level. It takes about 10-15hrs simultaneously.
The deshuttered panels are lifted & fixed on the floor .The activity requires 7-10hrs Kicker and External shutters are fixed in 7 hrs. The wall shutters are erected in 6-8 hrs. One of the major activity reinforcement requires 10-12 hrs. The fixing of the electrical conduits takes about 10 hrs and finally pouring of concrete takes place in these.
This is a well synchronized work cycle for a period of 7 days. A period of 10-12 hrs is left after concreting for the concrete to gain strength before the beginning of the next cycle. This work schedule has been planned for 1010-1080 sq m of formwork with 72-25cu m of concreting & approximate reinforcement.
The formwork assembling at the site is a quick & easy process. On leaving the MIVAN factory all panels are clearly labeled to ensure that they are easily identifiable on site and can be smoothly fitted together using formwork modulation drawings. All formwork begins from corners and proceeds from there.
The system usually follows a four day cycle: -
Day 1: -The first activity consists of erection of vertical reinforcement bars and one side of the vertical formwork for the entire floor or a part of one floor.
Day 2: -The second activity involves erection of the second side of the vertical formwork and formwork for the floor
Day 3: - Fixing reinforcement bars for floor slabs and casting of walls and slabs.
Day 4: -Removal of vertical form work panels after 24hours, leaving the props in place for 7 days and floor slab formwork in place for 2.5 days.
4.6 FEATURES OF MIVAN FORMWORK
1) Sheet Thickness & Panel Sizes
• The concrete face of panels (Al Sheet) is 4 mm thick.
• Standard sizes of Panels are: 2000x600, 2000x300, 1200x300, 850x300.
• Apart from above any size as required shall be manufactured and delivered.
2) Load Carrying Capacity
• High load carrying capacity of 7-8 Tonnes Per square meter
• Light weight is the main advantage over conventional formwork technology.
• Aluminium formwork weighs around 18-20 kg per meter square.
3) Cycle Time
High speed of construction can be achieved by this system that means faster completion of project. 7 Days per floor.
4) Striking time
• Vertical (Wall) Formwork – 12 hours after concreting or when concrete strength has reached 2N/mm2.
• Horizontal (Deck) Formwork – 36 hours after concreting or when concrete strength has reached 10N/mm2.
5) Pouring System
Monolithic pouring for:
• The panels are made out of Structural Grade Aluminium alloy.
• Around 200 repetitions can be achieved while using Aluminium Formwork System.
4.7 Design Aspects
The comparison is done between buildings constructed by: -
i) Conventional RC columns, beams, and slab construction (RC moment resisting frame d structure)
ii) RC load-bearing walls and slabs.
In the case of RC moment-resisting framed structures, the horizontal forces due to wind or earthquake are resisted by the frames resulting in the bending moments in columns to resist bending moment and vertical loads would be more than that required to resist vertical loads without bending moment. Similarly, additional reinforcement will be required in beams at supports. In the case of RC load-bearing walls, monolithic casting of slab along with RC walls results in a box type structure, which is very strong in resisting horizontal forces due to wind or earthquake. In view of large depth of shear walls, the resulting stresses due to bending moment and vertical loads are smaller and in many cases, concrete alone is capable of resisting these forces.
On evaluating these alternatives, it is seen that the beam column frame system in
i) Performs poorly against earthquake forces compared to RCC wall and slab construction. Recent changes in the IS Codes, as well as recommended good practice demand provision of additional reinforcement comply with ductility requirements.
ii) The sizing and detailing of columns needed to be –that they are 20% stronger than beams they support.
The cost per flat (or per m² built up area) using MIVAN shuttering system depends upon the number of repetition and period of completion of the project. As the formwork can be reused over 250 times, the initial cost per unit of forming area is less when compared to traditional methods. The reduction of cost is also due to the elimination of brickwork and plaster and also due to reduction in time. The cost of the project gets substantially reduced due to shear wall construction. These are due to the reduced consumption of steel, masonry, and plaster even though the use of concrete decreases. For the same number of repetition, the cost will be less if the period of completion is longer. This is because for a shorter completion period, the area of formwork is more than required for longer completion period. Cost of formwork is illustrated in Table 4.1.
The aluminium formwork provides an integrated scaffolding system which reduces the cost of scaffolding requirements. The mechanical and electrical installation is simplified as conduits are embedded in the structure by precise engineering of outlets and service ducts. Thus, we can conclude that the overall cost of the project is lesser when compared to project using traditional methods of formwork.
4.8.1 Cost comparison of mivan and conventional formwork
Initial cost of mivan formwork is high when compared with conventional formwork. Mivan formwork is economical when floors are typical and also labour cost for mivan is slightly less when compared with conventional formwork. Aluminium formworks are more durable, maximum repetition of 300 can be achieved where as in conventional maximum repetition of 10 can be achieved which makes aluminium formwork more economical.
Table 4.1 COST COMPARISON
Following the graphical representation of the above study of rates at the different rates of formwork. The chart shows the aluminium formwork is economical when the use of cycle. The steel formwork is economical than the other formwork.
Fig 4.25 Cost Analysis Graph
4.9 Comparison of Aluminum Form Construction Technique over
Table 4.2 Comparison Between Mivan and Conventional Form Work
5. HONEYCOMBING AND CRACKS IN SHEAR WALL
The mivan technology follows monolithic construction i.e. all the structural member viz. beam, shear wall, slab are casted at same time. In conventional construction the concrete is placed from height of 0.6 to 1 meter, and that is what recommended height to place the concrete. In Mivan Technology of construction the concrete is placed from height of 3 meter in shear wall and compacted using vibrator, now as height of placing concrete is more there are chances of segregation in concrete resulting in honeycombing and cracks in wall. In mivan construction it is generally happened that after removing formwork there is honeycombing in shear wall, in this project we had tried to fix the problem of honeycombing in shear wall. We had gone to BASF The chemical company pertaining this problem; they suggested us to use the MasterGlenium ACE 30JP as admixture to concrete so as to increase the workability of concrete to reduce honeycombing and increase the strength of concrete. One of the measures to check the workability of concrete is its slump and to check the strength is compressive strength. In this project we have compared the slump and strength of concrete using admixture and no admixture by slump cone test and compressive testing machine respectively. Following are the details.
A. Specification of MasterGlenium ACE 30JP
Appearance: Brownish Liquid
Specific gravity -1.02 g/cm3
pH Value: 6-9
B. Concrete mix design
Grade designation: M35
Type of cement: OPC 53 Grade
Reduced water content for admixture: 20 %
Conventional Concrete: 1:1.4:2.2
Concrete using admixture: 1:1.2:3.2
C. Slump cone test result
Table 4.3 SLUMP CONE TEST RESULT
D. Compressive strength testing result
Table 4.4 Compressive strength testing result
By using admixture the workability of concrete is increased by 120 % whereas the strength of concrete is increased by 13 %
6. THE ADVANTAGES AND DISADVANTAGES OF MIVAN:
The MIVAN formwork is specifically designed to allow rapid construction of all types of architectural layouts.
1) Total system forms the complete concrete structure.
2) Custom designed to suit project requirements.
3) Unsurpassed construction speed.
4) High quality finish.
5) Cost effective.
6) Panels can be reused up to 250 times.
7) Erected using unskilled labor.
Quality and speed must be given due consideration along with economy. Good quality construction will never deter to projects speed nor should it be uneconomical. In fact, time consuming repairs and modifications due to poor quality work generally delay the job and cause additional financial impact on the project. Some experts feel that housing alternatives with low maintenance requirements may be preferred even if the initial cost is high.
6.2 LIMITATION OF MIVAN FORMWORK:
Even though there are so many advantages of MIVAN formwork the limitations cannot be ignored. However the limitations do not pose any serious problems. They are as follows: -
1) Because of small sizes finishing lines are seen on the concrete surfaces.
2) Concealed services become difficult due to small thickness of components.
3) It requires uniform planning as well as uniform elevations to be cost effective.
4) Modifications are not possible as all members are caste in RCC.
5) Large volume of work is necessary to be cost effective i.e. at least 200 repetitions of the forms should be possible at work.
6) The formwork requires number of spacer, wall ties etc. which are placed @ 2 feet c/c; these create problems such as seepage, leakages during monsoon.
7) Due to box-type construction shrinkage cracks are likely to appear.
8) Heat of Hydration is high due to shear walls.
The task of housing due to the rising population of the country is becoming increasingly monumental. In terms of technical capabilities to face this challenge, the potential is enormous; it only needs to be judiciously exploited.
Civil engineers not only build but also enhance the quality of life. Their creativity and technical skill help to plan, design, construct and operate the facilities essential to life. It is important for civil engineers to gain and harness the potent and versatile construction tools.
Traditionally, construction firms all over the world have been slow to adopt the innovation and changes. Contractors are a conservative lot. It is the need of time to analyze the depth of the problem and find effective solutions. MIVAN serves as a cost effective and efficient tool to solve the problems of the mega housing project all over the world. MIVAN aims to maximize the use of modern construction techniques and equipments on its entire project.
We have tried to cover each and every aspect related to aluminium (MIVAN) form construction. We thus infer that MIVAN form construction is able to provide high quality construction at unbelievable speed and at reasonable cost. This technology has great potential for application in India to provide affordable housing to its rising population.
Thus it can be concluded that quality and speed must be given due consideration with regards to economy. Good quality construction will never deter to projects speed nor will it be uneconomical. In fact time consuming repairs and modification due to poor quality work generally delay the job and cause additional financial impact on the project. Some experts feel that housing alternatives with low maintenance requirements may be preferred even if at the slightly may preferred even if at the higher initial cost.
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