Experimental Study of GFRP-Reinforced Geopolymer Concrete Columns under Different Loading Conditions

This study discusses the behavior of ambient-cured circular geopolymer concrete specimens tested under different loading conditions. Twelve specimens were cast and tested to investigate the influence of the type of the reinforcement, that is, steel and glass fiber-reinforced polymer (GFRP), the pitch of the transverse reinforcement, and loading conditions (concentric axial load, 15 and 35 mm eccentric load, and four-point bending). The axial load carrying capacity, confinement efficiency, and deformability of the specimens decreased for the replacement of the steel reinforcement with the same amount of GFRP reinforcement under concentric and eccentric loads. However, the deformability of the GFRP reinforced concrete (RC) specimen was higher than the deformability of its steel counterpart specimen under four-point bending. Overall, the reduction in the pitch of the GFRP helices in the GFRP-RC specimens resulted in a significant improvement in the confinement efficiency, deformability, postpeak behavior, and the axial load-bending moment capacity of the specimens under different loading conditions. Moreover, theoretical equations based on the confinement pressure of transverse reinforcement provide accurate predictions of the theoretical load-carrying capacity of the columns reinforced with GFRP bars and helices.