Sustainable, Rapid, Affordable
Cost-effective and faster project deliveries are the key challenges in affordable mass housing. Through research works carried out for over a decade, IIT-Madras has developed a housing technology - glass fibre-reinforced gypsum (GFRG) - that is affordable, sustainable and environment-friendly, to address the need for rapid affordable mass housing in India. Over 1,200 houses in the country have already been constructed using this technology. Dr A Meher Prasad, Professor, Structural Engineering Division, Department of Civil Engineering, IIT Madras, shares more on the advantages of constructing with GFRG...
GFRG panels (commercially known as "Rapidwall"), made of high-quality gypsum plaster reinforced with special glass rovings, were first introduced in Australia in 1990. These lightweight hollow panels were originally intended for rapid wall construction as load-bearing walls.
In India, unlike Australia, we need to deal with earthquake-resistant design, as over 50 per cent of our population lives in seismically-prone areas with moderate to severe earthquakes. Hence, the GFRG building system had to be designed to meet the requirements of the prevailing standards of seismic resistance in India. Extensive studies had been conducted by a team of researchers of the Civil Engineering Department of IIT-Madras on the use of GFRG wall panels, with different infill (reinforced concrete) configurations, as structural walls, including earthquake-resistant design, and a detailed design methodology developed. The research extended the application of this product for the entire building system - including floors, roofs and staircases -with reinforced concrete embedded in every third cavity of panel, along with a layer of 50 mm screed concrete on top. Use of GFRG panels were found to be significantly reducing the consumption of reinforced concrete in such construction. The use of GFRG panels for walls, floors and staircases, appropriately designed for composite action with reinforced concrete, and with tie beams at all the wall-floor junctions, provided for a complete GFRG building system. Building Materials and Technology Promotion Council (BMTPC), under MoHUA, approved the use of GFRG for construction of buildings up to 10 floors in India, without the use of any beams and columns.
Manufacturing of GFRG panels
GFRG is a building construction technology that makes use of waste gypsum in India. While it can be manufactured out of any kind of gypsum, with the production process requiring relatively low energy, the panels are made from processed phosphogypsum in India.
Currently, GFRG panels are manufactured in India at Fertilisers and Chemicals Travancore, Kochi, to fixed dimensions of 12 m length, 3 m height and 124 mm thickness, with hollow cavities inside.
The applications of GFRG panels include lightweight load-bearing walls capable of resisting gravity and wind loads; shear walls resisting earthquake load, floor or roof slabs, infill or partition walls for framed structures; compound walls; etc. While the proposal is primarily for mass housing, it can also be used for individual houses and other buildings (with spans in one direction not exceeding about 4.5 m). This is a load-bearing construction, ie, with the walls going all the way down to the foundations.
The foundation for GFRG buildings can be based on conventional methods, depending on local site conditions. For low-rise GFRG buildings, it is sufficient to provide simple masonry spread footings with a network of reinforced concrete plinth beams on top, above which, the GFRG wall panels can be placed (with "starter bars" embedded in the plinth beams). If the depth of the foundation is high, the plinth beams can be framed to reinforced concrete pedestals that are provided with small isolated footings, properly designed. In the case of taller GFRG buildings, it is desirable to provide reinforced concrete walls below the plinth beams, with a suitable spread footing or raft below. Panels can be quickly installed with the help of cranes.
Advantages over conventional buildings
High speed of construction: GFRG demo building in IIT-Madras with four flats in two storeys (total 1,981 sq ft) built within a month.
Less built-up area for the same carpet area: Wall panels are only 124 mm thick.
Less embodied energy and carbon footprint: Significant reduction in use of cement, sand, steel and water; recycling of industrial waste gypsum.
Lower cost of structure: Savings in materials; no plastering.
Lesser building weight (panels weigh only 44 kg per sq m), contributing to savings in foundation and reduction in design for earthquake forces, particularly in multi-storeyed construction.
Buildings up to 8-10 storeys can be designed using this load-bearing system, without the need for beams and columns
Excellent finishes of prefabricated GFRG panels - used for all the walls, floors and staircases, with minimal embedded concrete:
No need for additional plastering The use of GFRG panels not only facilitates fast construction but reduces labour requirements.
Better thermal performance in comparison to conventional building.
Thermal performance and water-resistant properties
The thermal performance of the GFRG demo building at IIT-Madras was analysed through field measurements. In-situ thermal measurements showed that the GFRG demo building was around 2oC cooler compared to an adjacent conventional building during the harsh summer. Further, tests have shown that GFRG panels absorb less water.
The water absorption of the panels is found to be less than 2 per cent even after 24 hours of immersion in water; the panels are therefore water-resistant. But as GFRG buildings system are prefabricated systems, all the construction joints (including the vertical and horizontal wall panel joints) should be treated with waterproofing compounds.
GFRG is environment-friendly, as it utilises industrial waste, and the construction minimises the usage of scarce and energy-intensive materials such as cement, sand, steel and water. Since gypsum is an inert material, GFRG building construction entails far less embodied energy (from manufacturing to completion of construction) compared to conventional construction using brick, reinforced concrete or precast concrete. Hence, GFRG has been confirmed as a green material by the United Nations Framework on Climate Change (UNFCC).
This technology has been well demonstrated and the design procedure is now being codified. With increased production of GFRG panels across the country, it can serve as a sustainable solution for the Centre's Housing for All mission. A scheme for construction of 36, two-storeyed GFRG houses has been completed at Nellore by the Building Materials and Technology Promotion Council in 2016. Besides, five GFRG hostel buildings of four storeys each are currently under construction and nearing completion at the IIT-Tirupati transit campus with a built area of 1.4 lakh sq ft. Moreover, a structural design code has also been approved by the BIS, based on the extensive studies carried out on GFRG building systems. BIS has also published two draft standards for GFRG material specification and method of analysis and design of GFRG buildings.
Now, to take GFRG forward for mass housing in a big way in India, one needs easy availability of the panels in all regions, requiring manufacturing plants to be set up; builders taking up projects aimed exclusively for mass housing, using this technology; and training of skilled workers in erection and construction methods, as well as training for architects and structural designers. As of now, the panels are available only in Kochi.
Tried and Tested
With the idea of demonstrating this building system using the technology developed, a two-storey GFRG demonstration building of 1,981 sq ft was constructed at the IIT-Madras campus in 2013. The entire superstructure was completed and rendered fit for occupation within 29 days after the laying of the foundation. There was a saving of over 50 per cent in embodied energy for GFRG construction.
The demo building was constructed using glass fibre-reinforced gypsum panels, originally designed for use as walls by Rapid Building Systems, Australia. The IIT-Madras research group extended the application of this product for the entire building system - including floors, roofs and staircases û thus significantly reducing the consumption of reinforced cement concrete (RCC). The team also collaborated in the indigenous development of an excellent waterproofing material, which is essential for prolonged durability of GFRG panels, especially in the case of roofs and toilets.
Currently, the cost of GFRG construction stands at Rs 1,600-1,700 per sq ft. The GFRG demo building inside the IIT-Madras campus, covering a total plinth area of about 1,981 sq ft, costed about Rs 23 lakh. A comparison of the cost of this building with a conventional building of the same plan showed that the demo building was 25 per cent cheaper compared to the latter.