Glass-fibre reinforced concrete (GRC) is a material made of a cementatious matrix composed of cement, sand, water and admixtures, in which short length glass fibres are dispersed. It has been widely used in the construction industry for non-structural elements, like façade panels, piping and channels. GFRC offers many advantages, such as being lightweight, fire resistant, good appearance and strength. In this study, trial tests for concrete with glass fibre and without glass fibre are conducted to indicate the differences in compressive strength and flexural strength by using cubes of varying sizes. Various applications of GFRC shown in the study, the experimental test results, techno-economic comparison with other types, as well as the financial calculations presented, indicate tremendous potential of GFRC as an alternative construction material.
GLASS Fiber Reinforced Concrete (GFRC) or (GRC) is a type of fiber reinforced concrete. Glass fiber concretes are mainly used in exterior building façade panels and as architectural precast concrete. This material is very good in making shapes on the front of any building and it is less dense than steel. GFRC is a form of concrete that uses fine sand, cement, polymer (usually an acrylic polymer), water, other admixtures and alkali-resistant (AR) glass fibers. Many mix designs are freely available on various websites, but all share similarities in ingredient proportions.
Glass fibre reinforced cementitious composites have been developed mainly for the production of thin sheet components, with a paste or mortar matrix, and ~5% fibre content. Other applications have been considered, either by making reinforcing bars with continuous glass fibres joined together and impregnated with plastics, or by making similar short, rigid units, impregnated with epoxy, to be dispersed in the concrete during mixing.
Glass fibres are produced in a process in which molten glass is drawn in the form of filaments, through the bottom of a heated platinum tank or bushing. Usually, 204 filaments are drawn simultaneously and they solidify while cooling outside the heated tank; they are then collected on a drum into a strand consisting of the 204 filaments. Prior to winding, the Filaments are coated with a sizing which protects the filaments against weather and abrasion effects, as well as binding them together in the strand .
Following points emerged from a literature review:
– Glass fibres lose a proportion of their pristine strength when placed in a Portland cement environment. AR fibres have a superior performance to other types, and are likely to retain long term tensile strengths of about 1000-1200 N/mm2 at ambient temperatures in a cement environment .
– This includes not only an assessment of fibre content and matrix strength, but also such details as fibre distribution, orientation, and effectiveness of bonding. Possible manufacturing or materials faults can also be diagnosed. Also it shows that the MOR and LOP in drying condition test have higher result than wet condition around (1- 5) MN/m2 difference .
– The main difference between dewatered and non-dewatered GRC is the difference in density which has two effects. Firstly although the fibre content by weight is the same, the higher density of the dewatered board gives a higher fibre volume fraction giving higher strengths. Secondly the dewatered board has better compaction and reduced porosity giving better fibre/matrix bond strength .
– Cement, when reinforced with glass fibre, produces precast elements much thinner-typically 10 mm-than would be possible with traditional steel-reinforced precast concrete, where 30mm or more concrete cover to the steel is essential as protection against corrosion. Thinner sections are also made possible by the low water: cement ratio of the material, the lack of coarse aggregate, and its low permeability. As a result, panels of equal strength and function of precast concrete can be produced with thinner sections and therefore less weight .
– Special methods have been suggested to reduce the sensitivity to poor and non uniform water curing. The addition of polymer latex has been reported to be effective in eliminating the adverse effects of lack of water curing. It has been suggested that for AR-GRC, the addition of 5% polymer solids by volume, without any moist curing, may replace the recommended practice of seven days curing in a composite without the polymer .
– The tests conducted on GFRC in laboratory have shown good resistance for fire, since the major use of GFRCs is for architectural building panels. In these buildings, fire resistance becomes an important factor in design .
– When cement, mortar or concrete is splashed or otherwise brought into contact with window glass, etching occurs. This is because the alkali in cement attacks some of the silicates that are used in glass manufacture. The stock used in making glass fibres has better alkali resistance than window glass because zirconia is used as one of the constituents .
– Tests on telecommunication towers by using GRC with carbon fibre and/or stainless steel bars have shown that GRC can be used as structural material, with reduced weight and has good durability properties. According to the results of the tests performed in small specimens the average values of the main material properties are: compression strength: 41 MPa, tension strength: 3.7 MPa; initial Young modulus: 16.5
– The mixes with 1.5% volume of fibres gave optimum composite properties in terms of compressive strength with 25.39% strength improvement. The highest increase in split tensile strength was observed in mixes with 1.5% of volumes of fibres and found to be 5.76% higher strength than reference concrete. Similarly, the highest flexural strength was observed in mixes with 1.5% of volume of fibre and found to be 72.5% more than reference concrete .
Objectives Of The Study
In the study, the following objectives are envisaged:
– Study the mix design aspects of the GRC.
– Understand the various applications involving GRC.
– Compare GRC with alternatives such as stone, aluminum, wood, glass, steel, marble and granite.
– Perform laboratory tests that are related to compressive, tensile and flexure by use of glass fibre in the concrete pour.
Methodology Of The Study
In order to achieve the objectives set, data was collected from the field practices which are being followed in the building construction and from the factory manufacturing GRC. Data has been collected from different project sites and from different locations.
The data is collected from these resources:
– Yogi Group
– Grasim Company
– Durocrete Laboratory
– J. Kumar Infraproject Company
– Some project sites like, Della Tower, Sharad Pawar International School, Holakar Bridge…etc.
The type of data collected is to make comparison between GRC with other cladding materials aspect to costs, quality and techniques.
Also an attempt to show up how much building space is required to set up the factory, including all the initial costs and other investment costs, is made.
Other type of data related to experimental work at laboratory. Some tests on concrete with AR-Glass fibre is collected so as to gain differences between them, when using different ratios of glass fibre.
The aim of the study is to introduce glass fibre as an important construction material, with good resistance to alkali, good strength, high tensile and reducing shrinkage cracks. The data is presented as below:
Glass Fibre Reinforced Concrete Projects
– Yogi Project——GRC Work——-Taj Heritage Hotel-Mumbai
A balcony for room no.257 at hotel Taj Heritage was replaced by GRC. Original in RCC same old finish (100 years old) was achieved with same style. Balcony weight: 800 Kg. Cost: cost 250,000 Rs. Duration for replacement: 30 days
– Casting at J.KUMAR INFRAPROJECTS
Name of project: Holakar Bridge, Pune. Location: RMC plant, Holakar Bridge
Date of casting: 17/4/2010
Type of casting: normal concrete mixed with AR-glass fibre.
Mix proportion ratio:
Cement- 400 kg/m3
Micro silica (Silica fume) – 40 kg/m3
Standard sand- 1000 kg/m3
Glass fibre- 1% by weight of cement
Coarse aggregate- Nil
– Experimental program at J. Kumar concrete division
IV. Summary of the Test Results
There are some points, which can be concluded from the test results:
– Using glass fibre in conventional concrete has a limit by percentage to weight. The best amount to use is 1.5% of cement weight because good results are obtained as compared to other amounts of use.
– According to this result, increasing weight of glass fibre in normal concrete affects the cohesiveness between the particle of concrete and this results in degrading of compressive strength, flexural and tensile strength.
– For (M60) mix, a percentage of glass fibre of 2% gave a flexural strength of (6.15 MPa).
– Glass fibre does not effect on high performance concrete, if it especially contains big gradation of coarse concrete because it leaves more porosity and spaces between the particles and allows air to move between. One should try without coarse aggregate or only by using 10 mm coarse aggregate by using good condition of compaction to flow out air entraining.
– One should take care of glass fibre during mixing with concrete. It should be not allowed to mix more than 1 minute, otherwise it will be break to tiny pieces, and it cannot be worked with.
– GRC as a cladding material
Some important points of GFRC for using in cladding of buildings are indicated as follows:
– The materials have a good resistance for tension. That is the reason why Glass fibre is chosen as reinforcement for concrete. Right now, is used mostly for cladding buildings, lining, sewer pipe, shoulder of roads and etc…
– Compatibility of glass fibre with concrete or mortar helps us to use it easily in our daily project especially for façade of buildings, as we said AR-glass fibre that have good resistance to alkalinity that contains in cement (pH > 12.3) with high level.
– AR-glass fibre can control shrinkage cracks easily; it shows this property particularly in cladding purpose or rendering. Because of most important thing in GRC it is water: cement ratio maximum 0.35, which helps to control the shrinkage and bonding each other by glass fibre.
– GRC can be used as alternative material of natural stone, especially in those countries where stone is less or unavailable. Also for those countries that favour stone only, the cost is higher, but because of less maintenance one can return back this money.
– Changing GRC panel is very easy as compared to other cladding because of making GRC by panel and just installing on the site. Also if broken one panel can be repaired or removed and a new one can be put, but if stone or tile is broken, it is not easy to change.
– This material is eco-friendly material because it consumes less energy during production; one can use to control pollution and carbon dioxide which is dangerous to human life.
– GRC is a new growing industry in India, customer awareness is increasing and more projects have GFRC components.
– GFRC industry in India can be started anywhere. Existing manufactures do not have their units in city industrial areas.
– As of today GFRC cladding to building surface has emerged as main application on account of reasons as below;
– Alternative cladding materials like glass, aluminium have not performed well in Indian climate leading to leakages, warp pages, panels falling…etc.
– Granite, marble and PCC (Precast Cement Concrete) panels are very heavy compared to GFRC panels leading to site handling problems; there are major procurement problems with granite and marble.
– With GRC claddings building heat losses are minimum compared to aluminium and glass cladding. Civil aviation authorities have already taken decision to go for GRC claddings on their airport buildings.
– Facility to provide, indicate shapes, curves and profiles.
– One can impart any finish like stone, heritage, acid wash, flame hardened…etc on GRC panels which is not possible in other materials.
– GFRC manufacturers work on turnkey basis from concept to installation, where as for other materials one needs more than one agency.
– Suitability in earthquake prone areas.
– By adding suitable additives, GRC panels can be made
– Green’ which is not easily possible with other materials.
– Result and conclusion of glass fibre use in normal concrete
Depending on the tests results which are obtained, the following observations are made:
– Glass fibre helps concrete to increase compressive strength until indicated limit. A limit exists to a particular percentage from glass fibre mixed with concrete because increasing it affects on the bond of materials as is seen in the result. For 1.5% of cementitous weight gained best results are obtained as compared to other results.
– Air entrainment affects the ft/fc (tensile strength to compressive strength) ratio because the presence of air lowers the compressive strength of concrete more than the tensile strength particularly in the case of rich and strong mixes. The influences of in complete compaction is similar to that of entrained air or may be broken of fibre reasons to could not get good result of flexural and compressive strength.
– By using 20 mm of coarse aggregate more air entraining is increased in the concrete: use of only 10 mm coarse aggregate to solve problem of reduced flexural strength is advocated.
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2 Arnon Bentur and Sidney Mindess, “Fibre Reinforced Cementitious Composites”, Second Edition 2007, Chapter 8, (pp 278).
3 J.G. Ferreira, F.A. Branco 2005, “Structural application of GRC in telecommunication towers”, Construction and Building Materials Journal, August 2005.
4 Majumdar, A.J. (1974), “The role of the interface in glass fibre reinforced cement”, Building Research Establishment, 1974, Current Paper (cp 57-74).
5 M. Levitt 1997 “Concrete materials problems and solutions”, “GRC and Alkali-Glass reaction”, First Edition 1997, pp 22-24.
6 M.W. Fordyce and R.G. Wodehouse, “GRC and buildings”, First Edition 1983.
7 Perumelsamy N. Balaguru and Surendra P. Shah, “Fibre reinforced cement composites”, February 1992, Chapter 13, (pp 351).
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9 R .N. Swamy, “Testing and Test Methods of Fibre Cement Composites”, 1978, pp 42-43.
10 Surendra P. Shah, James I. Daniel and Darmawan Ludirdja, “Toughness of Glass Fiber reinforced concrete panels subjected to accelerated aging”, PCI Journal, September-October 1987, pp 83-88.
11 U. M. Ghare, “Manufacture of Glass Fibre Reinforced Concrete Products”, Unit 1, Division of YOGI group-UAE, August 2008.