Long Term Durability Studies on Glass Fibre Reinforced Concrete Using Rapid Chloride Permeability Test

Corrosion of reinforcing steel due to chloride ingress is one of the most common environmental attacks that lead to the deterioration of concrete structures. Corrosion related damage to concrete structures is a major problem. This durability problem has received widespread attention in recent years because of its frequent occurrence and the associated high cost of repairs. Chlorides penetrate crack-free concrete by a variety of mechanisms: capillary absorption, hydrostatic pressure, diffusion and evaporative transport. Of these, diffusion is predominant. Diffusion occurs when the concentration of chloride on the outside of the concrete member is greater than on the inside. This results in chloride ions moving through the concrete to the level of the rebar. When this occurs in combination with wetting and drying cycles and in the presence of oxygen, conditions are right for reinforcement corrosion.

The rate of chloride ion ingress into concrete is primarily dependent on the internal pore structure. The pore structure in turn depends on other factors such as the mix design, degree of hydration, curing conditions, use of supplementary cementitious materials and construction practices. Therefore, wherever there is a potential risk of chloride-induced corrosion, the concrete should be evaluated for chloride permeability.

Researchers all over the world are attempting to develop high performance concretes by using fibres and other admixtures in concrete upto certain proportions. In the view of the global sustainable developments, it is imperative that fibres like glass, carbon, aramid and polypropylene fibres provide improvements in tensile strength. Research in glass fibre reinforced concrete resulted in the development of an alkali resistance fibre (AR Glass fibres High Dispersion) that provided improved long term durability. In the present experimental investigation cylinders of 100 mm x 150 mm of M30, M40 and M50 grade concrete were cast with varying percentage of addition of 0.03, 0.06 and 0.10% of glass fibre. The rapid chloride permeability tests were conducted for a period of 180 days. The test results show that the addition of glass fibres exhibit better performance.