Failure mechanisms and damage evolution of geopolymer concrete beams under flexural loading: Experimental investigation and finite element analysis

This study investigates the failure behavior and damage mechanisms of geopolymer concrete (GPC) and ordinary Portland cement (OPC) reinforced concrete beams through a combined experimental and numerical approach. Flexural tests were conducted, and then displacement and crack development were monitored using high-precision total station measurements. Numerical analyses were performed using ABAQUS, and the consistency between experimental observations and numerical predictions was evaluated at yield and failure stages to characterize inelastic behavior and damage progression. The effects of key parameters, including tensile reinforcement ratio, geopolymer concrete formulations, and curing methods, on cracking behavior, stiffness degradation, and failure modes were investigated in detail. The results indicate that increasing the tensile reinforcement ratio enhances flexural stiffness and load-bearing capacity while reducing ductility at advanced damage stages. Compared to OPC beams, GPC beams exhibited narrower and more distributed crack patterns due to their distinct microstructural characteristics. Quantitatively, GPC beams exhibited approximately 15% greater deformation in the compression zone at failure, while tensile reinforcement strains were up to 23% higher at yield compared to OPC beams. In addition, the maximum crack width at failure in GPC beams was approximately 50% lower than that of OPC beams. These results indicate that, despite similar strength levels, GPC beams exhibit higher deformation capacity and more distributed damage behavior. The findings demonstrate that geopolymer concrete exhibits distinct failure characteristics compared to OPC and should be explicitly considered in structural design to improve damage control and failure prediction. Overall, the study highlights the potential of geopolymer concrete as a reliable and sustainable structural material.