Investigation on strength and ductility of confined geopolymer concrete subjected to axial loads

This paper presents the results of an investigation into geopolymer concrete confined by hoop reinforcement. The investigation focused on the strength and ductility of confined geopolymer concrete subjected to axial loads. The main objective of this research is to evaluate the strength and ductility behavior of confined concrete: by varying several confining reinforcement design parameters, like volumetric ratio, spacing, and yield stress. A total of 15 unconfined and confined geopolymer concrete specimens was produced and tested against axial loads. The test is carried out until the specimen collapses. Experimental results show that unconfined geopolymer concrete is highly brittle, characterized by very sharp post-peak behavior. The volumetric ratio, spacing, and yield stress of reinforcement play a significant role in determining the strength and ductility of confined geopolymer concrete. The comparison between the existing restraint models reviewed in the research was able to predict behavior before the peak of the experimental results very well. However, the existing confinement model has significantly different ductility behavior from the ductility behavior of the experimental results. In this research, an analytical expression of stress–strain for confined geopolymer concrete is developed by modifying the existing confinement model. The validation of confined concrete stress–strain between analytical expressions and experimental results is relatively close.