Structural behavior of GFRP reinforced concrete columns under the influence of chloride at casting and service stages

Corrosion attack due to chloride ions is a major problem found in steel reinforced concrete structures when subjected to marine environment. Glass fiber reinforced polymer (GFRP) has become an alternative reinforcement in marine concrete structures due to its excellent corrosion resistance, making it possible to combine with concrete composed of seawater and sea sand. However, the knowledge on the short-term and long-term properties of GFRP reinforced concrete columns is still limited. In order to facilitate the practical application of GFRP reinforced concrete in marine environment, the effect of chloride ions on the structural behaviors of GFRP reinforced concrete columns is investigated here. Numerous specimens consisting of GFRP reinforced concrete columns and steel reinforced concrete columns with different chloride concentrations were fabricated, conditioned and tested. The test results show that GFRP reinforced concrete columns cast with saturated water suffer a deterioration of 27.9% in load carrying capacity, but possess an enhancement of 104% in ductility when compared to those of specimens cast with distilled water. Meanwhile, it is observed that the GFRP reinforced concrete column possess a ductile failure mode, which indicates that the GFRP spirals can provide an effective confinement to the concrete core even in high chloride environment for a prolonged time. Such findings provide solid evidence to the feasibility and application of GFRP reinforced concrete in the offshore structures or artificial islands with great environmental and economic benefits.