G Sreenivasa, General Manager - Business Development, UltraTech Cement Limited, Bangalore
Introduction
Besides, food and clothing, shelter is a basic human need. India has been successful in meeting the food and clothing requirements of its vast population; however the problem of providing shelter to all is defying solutions. "While there has been an impressive growth in the total housing stock from 65 million in 1947 to 187.05 million in 2001, and as estimated that 26 million homes are required by 2012, to meet the large gap still exists between the demand and supply of housing units. The shortage of housing is acutely felt in urban areas-more so in the 35 Indian cities, which according to the 2001 census have a population of more than a million". ….. (Carol., 2005).
Trends in Housing Industry
With improve in economy, growth in IT/BT, Retail Business which attract major young unskilled, unemployed youths, shows least interest in construction jobs where one has to sweat very hard to earn his wages. With this, huge shortage of skilled/unskilled labour, construction of quality houses become difficult, lead to abnormal delays in completion of projects with cost overrun. The conventional method of construction in house building, labour availability & labour cost is going to be very critical & challenging for Housing industry in coming days, considering the Welfare Schemes announced by State/Central Govts towards improving the quality life of poor people in India.
Hence, for undertaking mass housing works, it is necessary to have less labour dependency, innovative technologies with mechanization, which are capable of fast rate construction and are able to deliver good quality and durable structure in cost effective manner
Hence, for undertaking mass housing works, it is necessary to have less labour dependency, innovative technologies with mechanization, which are capable of fast rate construction and are able to deliver good quality and durable structure in cost effective manner
RMD Technology
The rapid- monolithic- disaster proof construction practice is one of the options, to meet above all challenges, and thus, reduce the labour dependency, improves quality in construction, early delivery of project with budgeted cost.
The rapid-monolithic- disaster proof construction with aluminium formwork is an upcoming technology which has empowered and motivated the mass construction projects throughout the world. In this paper, discussed about practical approach of this technology with advantage of speed, quality, construction method and financial aspects, which is required for a successful completion of mass housing project. Also includes assembly of form work elements, loads to be considered in design, stages of construction and comparison of RMDC versus conventional system
The RMD construction works on following principles:
The rapid-monolithic- disaster proof construction with aluminium formwork is an upcoming technology which has empowered and motivated the mass construction projects throughout the world. In this paper, discussed about practical approach of this technology with advantage of speed, quality, construction method and financial aspects, which is required for a successful completion of mass housing project. Also includes assembly of form work elements, loads to be considered in design, stages of construction and comparison of RMDC versus conventional system
The RMD construction works on following principles:
- Rapid and best quality construction
- Offer unsurpassed customer satisfaction
- Competitive price
- Affords large degree of controls
- Change in Trust level between the Owner & Contractor community by way of quality, timely completion and at the same cost
- with motto in mind" "Cost is long forgotten, but Quality is remembered forever" and "House for all."
What Is RMD Technology?
The construction in which all the elements are cast together with rcc by using aluminium form/similar form work, which supports wall, beam, column, roof slab and other elements together for concreting in one go. This ensures absolutely no joints (monolithic) between the elements with great surface finish, hence highly durable & earthquake resistant. This is nothing but strong concrete house.
The construction process which involves minimum number of activities which can be simultaneously carried out with less time, exhibits highest quality and brings most durable, disaster proof, and cost effective buildings.
Earlier, The monolithic construction practice limited only to the dome structures, huge shell roof structures, special architectural buildings, large footings for foundation etc, where the structures have no joints, the performance and durability was utmost important. Similar practices were never used in housing construction rather never specified for monolithic construction in housing by designers may be due to less advancement in formwork technology and concrete technology.
The construction process which involves minimum number of activities which can be simultaneously carried out with less time, exhibits highest quality and brings most durable, disaster proof, and cost effective buildings.
Earlier, The monolithic construction practice limited only to the dome structures, huge shell roof structures, special architectural buildings, large footings for foundation etc, where the structures have no joints, the performance and durability was utmost important. Similar practices were never used in housing construction rather never specified for monolithic construction in housing by designers may be due to less advancement in formwork technology and concrete technology.
Selection of Formwork
When you choose aluminium forms, you are investing in highest quality and most durable formworks (over 100 repetition) which are custom designed from state-of-art plants. This ensures the accuracy of the building dimension, finish and quality work. No joints, No re-doing of work, no repair required. The construction of block masonry for walls, plastering of walls (external/internal) was totally eliminated. In Conventional practice, the electrical work will not only take time but also damage the block work (walls) before plastering. The time, labour, materials required for these activities are huge and eliminated in monolithic construction.
Merits of Aluminium Shuttering
- In contrast to most of the modern construction systems, which are machine and equipment oriented, the formwork does not depend upon heavy lifting equipment and can be handled by unskilled labors.
- Unsurpassed construction speed can be achieved due to light weight of forms, and less labor required for carrying the formwork.
- Construction carried out by this system has exceptionally good quality with accurate dimensions for all openings to receive windows and doors, right angles at meeting points of wall to wall, wall to floor, wall to ceiling, etc, concrete surface finishes are good to receive painting directly without plaster.
- Integral and smooth finishing of wall and slab of aluminum form work can be seen vividly on walls.
- Formwork components are durable and can be used several times without sacrificing quality or correctness of dimensions and surface.
Merits of Monolithic Construction:
- Higher carpet area, due to thinner shear wall construction and simplified foundation design for consistent/continuous load distribution.
- Monolithic construction of load bearing walls and slabs, produces structurally superior quality with very few construction joints, provides more seismic resistance to structure and highly durable than that of conventional column and beam slabs construction combined with brick or block work subsequently covered by plaster.
- The walls will not have plaster, problems associated with plaster cracks, etc. eliminated.
- Uniform quality will be achieved by using uniform grade of concrete for walls & columns and the natural density of concrete wall, result in better sound transmission coefficient. The maintenance cost of such structures will be negligible.
- In view of the 7 days cycle of casting a floor together with all slabs, as against 40-50 days cycle in the conventional method, completed reinforced concrete structure is available for subsequent finishing, uninterrupted progress can be planned, continuity maintained in each trade, thereby providing a scope for employing increased labor force on reducing finishing item. Hence, 2/3 of construction time in overall project period can be reduced.
- As the system establishes a kind of "Assembly line production," phase-wise completion in desired groups of buildings can be planned to achieve early utilization of the buildings.
Structural Components of Aluminium shuttering
1) Wall Components
- Wall panels, Rockers, Kickers, Stub-pins
- Beam side panels, Prop head for soffit beams, Beam soffit panels, Beam soffit bulkhead
- Deck panels, Deck props, Deck prop lengths, Deck mid beams, Deck beam bars, Soffit lengths, Soffit corners etc..
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Wall Assembly Details
Loads Acting on the Aluminium Formwork
In construction, the formwork has to bear, besides its own weight, the weight of wet concrete, the live load of 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 of. Thus, the design of the formwork is an essential part during the construction of the building.
For the design of planks and joints 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.
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:
For the design of planks and joints 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.
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
- 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.
Construction Stages
The concrete quality is most important, shall be cohesive and of good quality, specially designed for flowable, into forms without segregation and bleeding (slump of 140-160mm) is needed. The concrete shall be pumped by concrete pumps (preferably boom pumps or other pumps). This type of concrete can be sourced from reputed RMC suppliers.
The construction activities are divided as pre - concrete activities, during concreting and post - concrete activities. They are as follows:
The construction activities are divided as pre - concrete activities, during concreting and post - concrete activities. They are as follows:
Pre - concrete Activities:
- Receipt of Forms/Shuttering material on site as ordered
- Level Surveys - Level checking are made to maintain horizontal level check
- Setting Out - the setting out of the formwork is done
- Control / Correction of Deviation - Deviation or any correction are carried out
- Erect Formwork - the formwork is erected on site
- Erect Deck Formwork - Deck is erected for labour to work
- Setting Kickers - kickers are provided over the beam.
Things to look for during concreting:
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| Pictures show (RPD Technology) the details of reinforcement, aluminium formwork and finishes of G+3 buildings (courtesy PG Shetty’s Project Mysore) |
- Dislodging of pins / wedges due to vibration.
- Beam / deck props adjacent to drop areas slipping due to vibration.
- Ensure all bracing at special areas slipping due to vibration.
- Overspill of concrete at window opening etc.
The post-concreting activities include:
- Striking
- Cleaning
- Transporting
Aluminium Formwork Cycle Period
The system usually follows a 4- day cycle:
The above calculation does not include the additional cost-benefits such as the increased carpet area cost (5-8%), early occupational cost (4-5 months), and saving in interest cost, resources holding charges (4-5 months) etc.. as in case of conventional construction. The wastage of materials at site not accounted (3-5%). Also not considered the scrap value of Aluminium forms after 100 repetition (generally scrap value is higher compared to steel). Considering above, about 15-20% of overall cost shall be saved.
- 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 (roof slab)
- Day 3 - Fixing reinforcement bars for floor slabs and casting of walls and slabs
- Day 4 - Removal of vertical form work panels after 24 hours, leaving the props in place for 7 days and floor slab formwork in place for 2.5 days.
| Comparison of Speed of construction (For Typical Plan): | ||||
| Sl No | Desription of Activity | Conventional | RMDC | Remarks |
| 1 | Foundation | 30 | 16 | Excluding excavation 4 repetition |
| 2 | Plinth | 10 | 0 | |
| 3 | Columns | 15 | 0 | Includes curing |
| 4 | Beams | 10 | 0 | |
| 5 | Slab | 15 | 0 | Includes curing |
| 6 | Walls | 30 | 24 | 6- day cycle-4 repetition |
| 7 | Plastering | 30 | 0 | |
| Total | 140 days | 40 days | 3.5 times (1/3 of conventional) | |
| Note: In the above case Form work procured only ¼ of Plan area (4- repetitions per floor area) | ||||
The above calculation does not include the additional cost-benefits such as the increased carpet area cost (5-8%), early occupational cost (4-5 months), and saving in interest cost, resources holding charges (4-5 months) etc.. as in case of conventional construction. The wastage of materials at site not accounted (3-5%). Also not considered the scrap value of Aluminium forms after 100 repetition (generally scrap value is higher compared to steel). Considering above, about 15-20% of overall cost shall be saved.
Limitations
- Generally, used in mass housing project with same plan and the multi-storey structures having same plan area at all floors.
- Huge initial investment for formwork procurement- Clients can invest and issue to contractor
- Large number of repetitions makes this technology cost -effective.
- About 70-80% of formwork elements shall be useful for new project (new plan) after first project, rest shall be suitably designed and procured for next projects
- Initial setting of formwork at site (as demo), as per drawing dimension, may take more time
- The training of labor to handle designed formworks at site- however, this would overcome with support of formwork suppliers
- All the utilities, have to lay & embedded in concrete walls/slabs, hence relocation, repair of these will be very difficult.
- Since, structure is monolithic and wall thickness is less, these houses are little warmer than the conventional during summer/ sunny days. However, this problem can be overcome by using suitable thermal insulated paint for external wall or by adopting simple thermal insulation techniques or growing creepers & plants around the external walls.
| Sl No | Description of Item | Conventional | RMDC | Remarks |
| 1 | Initial investment on Aluminium Form- work | Nil | Rs 300 / sqm | Rs 10000 per sqm -life of 100 repetition |
| 2 | Handling charges | Nil | Rs 100 / sqm | |
| 3 | Solid Block work for Wall(8”thick) | Rs 850 / sqm | Nil | Market price |
| 4 | Plastering for walls(Both side) | Rs 175 /sqm | Nil | Market price |
| 5 | M25 grade- Ready mix concrete | Nil | Rs 500 /sqm | Rs 3800/cum |
| 6 | Steel for Shear walls | Nil | Rs 200/sqm | Rs 40000/MT |
| 7 | Miscellaneous | Rs 100 /sqm | Rs 100 / sqm | |
| Total | Rs 1125/sqm | Rs 1200/sqm | ||
Conclusion
Population explosion has always been a bottleneck to the development for Indian society especially providing housing for economically weaker sections (EWS) and low income groups are both gigantic and a complex problem. India desperately needs a lot of rapid dwelling units. Mass housing projects with RMDC technique is one of the solutions to the overgrowing problem. The speed & quality construction drives this technology;
- Cost effective - average 15% cost saving for load bearing wall over conventional timber/plywood shuttering
- Increased Carpet area/Usable floor space of (5 - 8%) over Conventional Design
- Speedy construction - 1/5th - 1/6th of time required to complete construction against the conventional
- Easy to use, since it’s simplified design
- Monolithic construction-box type strong structures with minimum/ no joints
- Structures are better earthquake and wind resistant
- Highly durable structures - required least maintenance
- Smooth finish of wall/roof/floor- ready to take the paint
- Block/Brick masonry eliminated thus Internal & External Plaster eliminated
- Environment-friendly - no wood/timber used
- Formwork-Lightweight section are used-hence easy to lift and used
- Only hammer required to erect - joining by simple pins & wedges and horizontal ties
- Aluminium shuttering material has higher scrap value compared to plywood/steel
