GLASS FIBER REINFORCED CONCRETE

ABSTRACT:-
Glassfibre Reinforced Concrete or GRC is one of the most versatile building materials available to architects and engineers. Composed principally of cement, sand and special alkali resistant (AR) glassfibres, GRC is a thin, high strength concrete with many applications in construction.
The GRC-Glass Fibre Reinforced Concrete, which was first invented by 'pilkington' in UK and developed successfully by rest of the continent, is a product having unique combination of properties unchallenged by any other existing material in the construction industry.
Glass Fibre Concrete can be moulded into wide varieties of shapes and contours to become an architectural element of any building. In fact CRC is tailor made; it can take any profile or shape as per consumer's requirement. This flexibility is what gives the material its tremendous demand in a wide ranging variety of applications.
INTRODUCTION :-
WHAT'S GRC?
Glass Fibre Reinforced Concrete (sometimes called Glass Fibre Reinforced Cement) is a mixture of Cement, fine aggregate, water, chemical admixtures and Alkali Resistant Glass Fibres.
There are a number of different manufacturing processes, the most common are Hand Spray and Premix.
Glass Fibre Reinforced Concrete (GRC) is a material which today is making a significant contribution to the economics, to the technology and to the aesthetics of the construction industry worldwide.
The Alkali Resistant Glass fibre is generally used at the 3 to 5% level in Hand Spray GRC Process and 2 to 3% in Premix GRC Process to manufacture of factory finished prefabricated products.
ROLE OF FIBRES:-
When the loads imposed on concrete approach that for failure, cracks will propagate sometimes rapidly, fibres in concrete provide a means of assisting the growth. Reinforced Steel bars in concrete have the same beneficial effect because they at as long continuous fibres. Short discontinuous Glass Fibre has the advantage, however, being uniformly mixed and dispersed throughout the concrete.
WHY "ALKALI RESISTANT" GLASS FIBRE MUST BE USED IN GRC?
When specifying the constituent materials of Glassfbire Reinforced Concrete it is an essential part of the overall Quality and Quantity Assurance in GRC products that a high zirconia alkali Resistant Glass fibre is used to manufacture GRC products.
The reasons for this are clearly illustrated. Figure-1 shows the loss in weight of Glass Fibres held in a saturated cements solutions (PH=12.9) for 200 Hours at 80 degree Celsius ploated against the Zirconia content. As is seen, the higher the Zirconia cotent the lower the weight loss.
Figure-2 visually illustrates the difference between high Zirnonia Alkali Resistant Glassfibres and standard E-glass, the type of glassfibre generally used in polyester resins and gypsum, quickly deteriorates and loses strength, where as the high Zirconia Resistant Glassfibre remains virtually unaffected.
The cost of the Zirconia makes Alkali Resistant Glassfbires considerably more expensive than E-glass but, as seen the price for security is well work paying.
GRC promise of thinner and stronger elements, reduced weight (1/3rd of Precast Concrete) and controlled cracking by simply adding a small amount of fibres an attractive feature of Fibre Reinforced Concrete.