Investigation on torsional behavior of geopolymer concrete members

This study investigates the pure torsional performance of Geopolymer Concrete (GPC) members using a self-designed loading device. The parameters investigated include concrete strength, stirrup ratio, and longitudinal reinforcement ratio. A total of 17 test members were designed, including three control members using Ordinary Portland Concrete (OPC). Through the tests, failure modes, crack propagation, torque-angle of twist curves, torque-reinforcement strain curves, and torque-concrete strain curves of the members were obtained. The influence of various parameters on the torsional performance of GPC members was investigated. The findings suggest that the failure modes of GPC members closely resemble those of OPC members, with similar ultimate torques. However, GPC members exhibit a lower cracking torque and more densely distributed cracks. The post-cracking stiffness of GPC members is slightly influenced by the concrete strength and increases with the stirrup ratio and longitudinal reinforcement ratio. The cracking torque of GPC is significantly influenced by the concrete strength grade. Lastly, the study discusses calculation formulas for the main crack inclination angle, cracking torque, and ultimate torque of the members, and modifies the ultimate torque formulas based on experimental results.