Effect of Stress Corrosion on Relaxation of Large Diameter BGFRP Bars

Fibre reinforced polymer (FRP) rebars do not corrode like steel rebars when they are exposed to moisture such as water. Instead they have been shown to degrade when exposed to alkaline media and, in some cases, acids. It has especially demonstrated extensive deterioration when it has been simultaneously stressed and exposed to harsh environments. This combined effect has been termed as stress corrosion. The effect of stress corrosion on the stress relaxation of large sized prestressed basalt-glass fibre reinforced polymer (BGFRP) bars was analyzed by laboratory experiments. Two stressed bars were submerged in aqueous solutions of acid and alkaline in two separate plastic tanks under constant strain. Stress reduction values were observed over a period of about 7 months. Bars immersed in acid bath had an average stress relaxation of 9.2% and that in the alkali bath was observed to be about 13.4%. These results support earlier assertions that exposure of GFRP bars to alkali media is likely to be detrimental to the long-term durability of the reinforced structure.