When Ar. Sanjay Puri designed 72 Screens, Jaipur, the project became a sensation. What is striking in that project is the use of perforated screen or Jaali, a reminiscent from the rich Rajasthani heritage that clads the entire façade of the building.
Designed to cater the blistering heat of Jaipur, the building is enveloped in abstract folded planes of perforated 3D screens that reduce the heat gain. Additionally, the light weight panels made the installations fast and without the need for heavy lifting further reducing the weight of the structure.
These panels were made out of Glass Fiber Reinforced Concrete, sometimes called GRC or GFRC, an interesting composite having high strength alkali resistant glass fiber embedded in a cementitious mix having numerous applications.
SURFACES REPORTER, in this article, has tried to understand the material, its composition and various applications.
Unlike the traditional Pre-cast reinforced concrete that relies on steel as the reinforcement, Glass Fiber Reinforced Concrete (GFRC), is a homogenously dispersed network of tiny strands of glass in the slurry of cement and sand. Concrete is used as a building material primarily because of its resistance to aging and its compressive strength. By using glass fibers as the matrix-bound by cementitious adhesion, substantial increases in flexural, tensile and impact strengths are achieved without losing the superb ageing properties of concrete.
According to www.stonewear.com, early efforts to incorporate glass fiber in a concrete matrix date back to 1941. These efforts failed because the alkaline environment present in a portland cement composite rapidly eroded plain glass fibers. The Great Britain Building Research Establishment succeeded in making an alkaline- resistant (AR) glass fiber in 1967 by adding zirconia to the fiber manufacturing process. The AR process was further refined by the Pilkington Corporation in the U.K.
Glass fiber Reinforced concrete (GFRC/ GRC) is generally manufactured by either the "spray" process or the "premix" vibration casting process. The method chosen is normally dictated by factors such as strength requirements, size of mould, architects specification etc. Sprayed GFRC is generally stronger than premix vibration cast GFRC. The reasons for this are, firstly, with sprayed GFRC it is possible to achieve a fiber content of 5 - 6% whereas premix GFRC is limited to around 3 - 3.5%. Secondly, Sprayed GFRC has lower water content than Premix GFRC.
Sand and cement are typically used at a ratio of about 1 to 1, although some mix designs call for slightly higher cementitious materials content.
The fibers are added to the mix at about 2% to 3% premixed GFRC or 4% to 6% by weight for spray-up mixes.
Many GFRC experts also use silica fume, metakaolin, or other pozzolans in their mix. This reduces the permeability of the concrete, making it more water-resistant and also reduces the alkalinity of
the concrete, which means it doesn't affect the glass-both of these factors mean increased concrete durability.
GFRC is a versatile material with numerous design applications:
Flexibility- GFRC has the characteristics to be cast into almost any shape hence has numerous applications.
Thickness- Thickness of GFRC varies as per the size of the panel, from 12 to 25 mm. GFRC can be cast in any size but we need to see the transportation constraints.
It could be up to 8’ x 4’.
Light-weight- GFRC weighs only one-third of the original solid concrete weight. This makes it ideal for outdoor or indoor applications where lightweight and durable concrete is needed.
Structural part- GFRC is not a structural element. It is just cladded on the structure, and it is not designed to take any structural load.
Corrosiveness- Having no steel as reinforcement, there’s no chance of any corrosion in GFRC. Hence it is more durable than any other substitute.
Flammability- GFRC consists of materials that are unlikely to burn. The concrete takes the role of a thermal regulator while exposed to fire and protects the materials from the flame heat.
Density- The elasticity and density of the GFRC are greater than precast concrete. The cement to the sand ratio for GFRC is approximately 1:1, while for precast concrete it is 1:6.
Impact strength and water permeability- The glass fibers included reinforcing the concrete produce considerably greater impact strength and lower permeability to water and air than precast concrete. GFRC looks like a natural stone and permits the designer greater flexibility in form, color, and texture.
Reinforcement- Since GFRC is reinforced internally, there is no need for other kinds of reinforcement, which can be difficult to place into complex shapes.
Toughness- GFRC doesn't crack easily-it can be cut without chipping.
Recyclability- Once used, GFRC panels
cannot be recycled.
According to GFRC guide available on Birla White Cement website, the typical applications of GFRC include:
Architecture- Prefabricated architectural cladding, architectural mouldings and features , Environment & Landscaping.
Building- Industrial and agricultural roofing, Walls and Windows, Renovation, Foundations and Floors, Modular Buildings.
Engineering- Permanent Formwork, Utilities, Acoustics, Bridges and Tunnels, Water and Drainage.
GFRC & Its future
So far, GFRC as a material has proved its mettle since last three decades. It has been used well for indoor as well as outdoor applications. The composite, with its low consumption of energy and natural raw materials, is being formed into a great variety of products. According to its manufacturers, the material has great possibilities and the future seem very bright. “On using GFRC elements one can express the creative best in terms of blending design elements that add life to a façade namely panels, grills, cornice, columns, balustrades, brackets, arches, door & window surrounds, domes, and many more, and these elements could be made to desired shape, size & colour, moreover a stone finish could be achieved that eliminates the painting. I really do not see any other building material that is even near to GFRC, wherein an architect can express better,” says Srihari Nilkar, Partner, GRC India Co.
However, there are some considerations to be done before using GFRC. The biggest is pricing as it is said to be higher placed than its counterparts. Mukul Gupta, MD, Ecoearth Solutions OPC Pvt Ltd. thinks that price cannot be deterrent in the growth of GRFC due to modern look, finish, color, as well as moldability aspect. Surfaces Reporter has come across observations that over a long period of time, GFRC may lose its strength. Moreover, GFRC requires forward planning as it is made pre-cast rather than on site. So once designed, altercations in structure is costly & time consuming. We will continue our research and get back with more information on this material.
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