The mammoth size of the program of providing houses to the homeless has forced the government to look beyond conventional construction practices of energy intensive building materials based on natural resources and to introduce fast track emerging technologies, which not only bring speed & quality but are safe, durable leading towards sustainable development. The Building Materials & Technology Promotion Council (BMTPC) under the guidance of Technology Sub Mission and Mission Directorate in the Ministry of of Housing & Urban Poverty Alleviation has identified and evaluated sixteen such technologies from different agencies. Here is brief look at them for their use in mass housing programme.
Monolithic Concrete Construction System – using Plastic – Aluminium Formwork
In this system, in place of traditional RCC framed construction of columns and beams; all walls, floors, slabs, columns, beams, stairs, together with door and window openings are cast-in-place monolithically using appropriate grade of concrete in one operation. The specially custom designed modular formwork made up of Aluminium-Plastic Composite is used for the purpose which facilitates easy handling with minimum labour & without use of any equipment. Being modular formwork system, it enables fast construction of multiple/mass modular units.
Economies of scale depend upon the volume of work and number of repetition of the formwork. To achieve economy, minimum 100 repetitions are desirable. For very small project of less than 500 units, this system may not prove to be economical. However, now with number of formwork manufacturers available, the project with less number units may also be feasible.
Monolithic Concrete Construction System – using Aluminium Formwork
Like Monolithic Concrete Construction System – using Plastic – Aluminium Formworksystem, here also, in place of traditional RCC framed construction of columns and beams; all walls, floors, slabs, columns, beams, stairs, together with door and window openings are cast-in-place monolithically using appropriate grade of concrete in one operation. However, instead of Aluminium-Plastic Composite formwork, the specially custom designed modular formwork made up of Aluminium is used which is easy to handle with minimum labour & without use of any equipment. Being modular formwork system, it facilitates in rapid construction of multiple/mass modular units.
Tunnel formwork is a mechanized system for cellular structures. It is based on two half shells which are placed together to form a room or cell. Several cells make an apartment. With tunnel forms, walls and slab are cast in a single day. The structure is divided into phases. Each phase consists of a section of the structure that will cast in one day. The phasing is determined by the program and the amount of floor area that can be poured in one day. The formwork is set up for the day’s pour in the morning. The reinforcement and services are positioned and concrete is poured in the afternoon. Once reinforcement is placed, concrete for walls and slabs shall be poured in one single operation. The formwork is stripped the early morning next day and positioned for the subsequent phase.
The formwork is manufactured in a fully automated plant. Presently, it is imported from France and there is no plant in India.
However, major limitation of this technology is that the floor spans executed with movable forms shall not be more than 5.60 m, unless accessory units are used. Also, the thickness of vertical in-situ walls shall not be more than 120 mm, unless justified by special provisions.
Sismo Building Technology
Sismo Building Technology is an insulating shuttering kit for whole building based on a three-dimensional lattice made of galvanized steel wire. The lattice is filled with materials of different nature to serve as formwork. The basic structure of the Sismo building module is steel wire lattice. At the exterior sides of the lattice, infill panels are inserted, which transform the lattice into a closed structure that can be filled with concrete. The type of infill panels used depends on the purpose of the wall: load bearing or not, insulated or otherwise, etc. The steel wire also acts as armature and anchoring for the finished material and it holds reinforcement bars in place during concrete filling.
Advanced Building System – EMMEDUE
Expanded Polystyrene (EPS) Core Panel System is based on factory made panels, consisting of self-extinguishing expanded polystyrene sheet (generally corrugated) with minimum density of 15 Kg/m3 , thickness not less than 60-mm, sandwiched between two engineered sheet of welded wire fabric mesh, made of high strength galvanized wire of 2.5-mm to 3-mm dia. A 3-mm to 4-mm dia galvanized steel truss wire is pierced completely through the polystyrene core at the offset angle for superior strength and welded to each of the outer layer sheet of steel welded wire fabric mesh. The panels are finished at the site using minimum 30-mm thick shotcrete of cement & coarse sand in the ratio of 1:4 applied under pressure. The shotcrete coat encases the EPS Core with centrally placed steel welded wire fabric mesh.
The technology (developed about 30 years back) has been successfully used in many countries like Morocco, Algeria, South Africa, Kenya, Austria, Malaysia, Ireland, Romania & Australia with involvement of different agencies and brand names.
The viability depends upon the quantum of work. Generally requirements of 1.5 lakh sq.m of panel per year for minimum period of three years makes the plant viable.
The Rapid Panel is a prefabricated assembly of high-strength steel wire forming a panel with a core of expanded polystyrene (EPS). During construction, Rapid Panels are installed as walls and/or slabs. Specified mixtures of mortar or concrete are applied to the surfaces of the panels to complete the structure.
The basic unit of the Rapid Panel is the zig-zag truss. Steel wire is bent into a zig-zag shape to form a continuous chain of web members. This bent wire is then welded to continuous chord wires at every node to form the complete truss.
The Rapid panels are manufactured in a fully automated plant. This technology was initially developed in USA and the Indian firm has a collaboration with WorldHaus, California, USA. These panels are manufactured in Mexico and there is no plant in India at present.
Reinforced EPS Core Panel System
Reinforced Expanded Polystyrene Core (EPC) Panel System is a factory produced panel system for the construction of low rise buildings upto G+3 and as filler walls in high rise RCC and steel frame buildings. In this technique, a core of undulated polystyrene is covered with interconnected zinc coated welded wire mesh on both sided reinforcement and shortcrete concrete.
The panels are finished on site by pouring concrete (double panel, floors and stairs) and spraying concrete to realise the following different elements of the system:
- Vertical Structural Walls
- Horizontal Structural elements
- Cladding elements
QuickBuild 3D Panels
In quick build 3 D Panel system, the panels consist of fire resistant grade insulated polystyrene core, two engineered layers of Galvanized Steel Mesh and galvanized steel trusses. The steel trusses are pierced through the polystyrene core and welded to the outer layer sheets of Galvanized steel mesh.
The wall panel is placed in position and a wythe of structural plaster is applied to both sides. The wall panel receives its strength and rigidity from the diagonal cross wires welded to the welded-wire fabric on each side. This combination produces a truss behavior, which provides rigidity and shear terms for a full composite behavior.
The shell of the structure is built by manually erecting the panels directly onto the slab with reinforcement rods. Desired utilities like doors, windows and ventilators may be pre-built while plumbing, electrical conduits may be added onsite. These panels are used in the construction of exterior and interior load-bearing and non-load bearing walls and floors of buildings of all types of construction.
Concrewall Panel System
The Concrewall System is an industrial system for the construction of structural walls of reinforced concrete for building in single panel up to G+3.
The system is composed of a factory produced panel of undulated (wave shape) polystyrene covered on both sides by an electro-welded zinc coated square mesh of galvanized steel and linked by 40 connectors per sq m made of high-elastic-limit, 3 mm dia wires realizing a 3 dimensional hyper-static reinforced steel.
The panels are assembled on site and in-situ concrete (double panels, floors, stairs) and shotcreted concrete sprayed (single panel) to realize the following different elements of the system:
- Vertical structural walls
- Horizontal structural elements
- Cladding element
- Internal walls
Glass Fibre Reinforced Gypsum (GFRG) PanelBuilding System
Glass Fibre Reinforced Gypsum (GFRG) Panel also known as Rapidwall is made-up of calcined gypsum plaster, reinforced with glass fibers. The panel was originally developed by GFRG Building System Australia and used since 1990 in Australia for mass scale building construction. In recent times, these panels are being produced in India and the technology is being used in India.
The panel, manufactured to a thickness of 124mm under carefully controlled conditions to a length of 12m and height of 3m, contains cavities that may be unfilled, partially filled or fully filled with reinforced concrete as per structural requirement. Experimental studies and research in Australia, China and India have shown that GFRG panels, suitably filled with plain reinforced concrete possesses substantial strength to act not only as load bearing elements but also as shear wall, capable of resisting lateral loads due to earthquake and wind. GFRG panel can also be used advantageously as in-fills (non-load bearing) in combination with RCC framed columns and beams (conventional framed construction of multi-storey building) without any restriction on number of storeyes. Micro-beams and RCC screed (acting as T-beam) can be used as floor/ roof slab.
The GFRG Panel is manufactured in semi-automatic plant using slurry of calcined gypsum plaster mixed with certain chemicals including water repellent emulsion and glass fibre rovings, cut, spread and imbedded uniformly into the slurry with the help of screen roller. The panels are dried at a temperature of 2750C before shifting to storage area or the cutting table. The wall panels can be cut as per dimensions & requirements of the building planned.
It is an integrated composite building system using factory made prefab load bearing cage panels & monolithic cast-in situ RC infilled for walling & floor/roof slab, suitable for low rise to medium rise (single to 10 storeys) building.
Light Gauge Steel Framed Structures
Light Gauge Steel Framed Structures (LGSF) is based on factory made galvanized light gauge steel components, designed as per codal requirements. The system is produced by cold forming method and assembled as panels at site forming structural steel framework of a building of varying sizes of wall and floor.
The basic building elements of light gauge steel framing are cold formed sections which can be prefabricated at site using various methods of connection. The assembly is done using special types of screws and bolts.
Cold formed sections are widely used in construction including residential floors, industrial buildings, commercial buildings, hotels and are gaining greater acceptance in the residential sector. LGSF is a well-established technology for residential construction in North America, Australia and Japan and is gaining ground in India.
LGSF is typically ideal for one to three storey high buildings, especially for residential and commercial buildings. Due to its flexibility, fast construction and durability, this technology has great potential for counties like India.
LGSF can be combined with composite steel / concrete deck resting on light steel framing stud walls. Apart from having potential for mass housing, modular buildings can be used for long term temporary or permanent structures such as schools and classroom, military and civil housing needs, post – disaster relief structures andindustrial buildings. Advisable maximum span for LGSF buildings should be 7.5-m.
Light Gauge Steel Framed Structure with Infill ConcretePanel (LGSFS-ICP) Technology
Light Gauge Steel Framed Structure with Infill Concrete Panels (LGSFS-ICP) Technology is an innovative emerging building and construction technology using factory made Light Gauge Steel Framed Structure (LGSFS), lightweight concrete and precast panels. The LGS frame is a “C” cross-section with built in notch, dimpling, slots, service holes etc. produced by computerized roll forming machine. These frames are assembled using metal screws to form into LGSF wall and roof structures of a building. Provisions for doors, windows, ventilators and other cutouts as required are incorporated in the LGSFS.
Factory Made Fast Track Modular Building System
Factory Made Fast Track Modular Building System comprises of prefabricated steel structure with different walling components. About 70 percent of the work is done in the factory with minimal usage of concrete, which enables system to deliver the building within a few days of work at site. The steel moduled are pre-fitted with flooring, ceiling tiles, electrical and plumbing fittings. The assembled steel modules are transported to the site for installation which is done using crane and other required machineries. Once all the components are assembled and erected at site, factory made 3–D Expanded Polystyrene (EPS) wall panels are fixedand shotcreting is done from both sides.
The uniqueness of system is the efficient and simultaneousactivities of site preparation and building construction infactory, rather than two phased customary process.
Speed Floor System
The Speed Floor System is a suspended concrete flooring system using a roll formed steel joist as an integral part of the final concrete and steel composite floor. It is essentially a hybrid concrete/steel tee-beam in one direction and an integrated continuous one-way slab in other direction. The joists of different depths are manufactured from pre-galvanized high tensile steel in a one pass roll former, where it is roll formed, punched, pressed and slotted in a fully computerized machine. The joist depth and the concrete thickness are varied depending on the span, imposed loads and other functional considerations. The Speedfloor composite floor system is suitable for use in all types of construction. The Speedfloor joists are designed and custom manufactured to suit particular job conditions.
Waffle Crete Building System
Waffle-Crete Building System consists of large, structural, ribbed panels of reinforced precast concrete, bolted together and the joints between the panels are caulked to form the walls, floor and pitched or flat roofs of buildings.
The surface of each panel consists of 51-mm thick slab or skin, stiffened with the ribs around the perimeter and across the panel, giving an overall panel thickness of 152-mm or 203-mm.
In single storey buildings, floors are constructed using precast reinforced concrete floor panels supported on precast concrete grade beams on well- compacted earth. The walls are constructed of 152-mm thick wall panels of precast reinforced dense concrete.
For buildings of more than one storey, the walls are supported on foundations designed as per the soil condition. A concrete apron are laid around the perimeter of buildings where there is a danger of water or wind erosion of the ground adjacent to the building. Metal or timber window and door frames are incorporated into the wall panels during casting or fitted after erection into openings that are formed in the panels during casting.
Internal walls consist of either reinforced precast concrete ribbed panels, conventional masonry walls or concrete walls. Where precast concrete panel or masonry internal walls are used in single storey buildings, these are normally be erected on a concrete surface bed or on concrete strip footings and not on suspended floor.
Services like water supply and electricity shall be normally accommodated in preformed slots in the ribs of panels, before the walls are lined. The casting can be done in casting yard while foundation is done, which reduces the construction time. Curing time is reduced by trapping the moisture generated from the concrete. The building after construction can be shifted from one place to another as the structure is joined using bolt connections.
Precast Large Concrete Panel System
Precast Large Construction Panel (PLCP) system consists of various precast elements such as walls, beams, slabs, columns, staircase, landing and some customized elements that are standardized and designed for stability, durability and structural integrity of the building. Precast residential building construction involves design, strategic yard planning, lifting, handling and transportation of precast elements. This technology is suitable for construction of high rise buildings resisting seismic and wind induced lateral loads along with gravity loads. The building framing is planned in such a way that maximum number of repetitions of moulds is obtained. These elements are cast in a controlled factory condition. The factory is developed at or near the site which provides an economical solution in terms of storage and transportation.
Industrialized 3-S System using Precast RCC Columns, Beams & Cellular Light Weight Concrete Precast RCC Slabs
The industrialized total prefab construction technology, being used since 1972, is based on factory mass manufactured structural prefab components conforming to provisions of relevant Indian Standards. The major precast elements are:
- RCC hollow columns with notches
- RCC solid beams (T/L/Square Shape)
- RCC precast slab
- AAC precast slab
- AAC precast block
In the system, precast dense concrete hollow column shell of appropriate sizes are used in combination withprecast dense concrete rectangular / ‘T’ shape / ‘L’ Shape beams with light weight reinforced autoclaved cellularconcrete/Precast RCC slabs for floors and roofs. The hollow columns are grouted with appropriate grade of in situconcrete. All the components and jointing of various structures are accomplished through on-site concerting alongwith secured embedded reinforcement of appropriate size, length and configuration to ensure monolithic continuousresilient, ductile and durable behaviour. Autoclaved Aerated Concrete (AAC) slabs can be used as floor / roof slabs.
Joints are filled with reinforced screed concrete (minimum 40 mm thick) of M20 grade minimum. RCC screed is laid over entire area of slab before flooring / water proofing.