Experimental and statistical comparison of fracture and fatigue performance of notched geopolymer and conventional concrete beams

Sustainable alternatives to conventional concrete are gaining attention, and fly ash-based geopolymer concrete (GPC) is emerging as a promising material because of its potential for a lower carbon footprint and improved mechanical performance. However, existing studies lack detailed comparison of fracture and fatigue behavior of plain fly ash-based GPC with PCC at similar compressive strengths. This study investigates and compares the fracture and fatigue performance of fly ash-based plain GPC with ordinary Portland cement-based plain cement concrete (PCC) having the same compressive strength (M25) by conducting experiments on notched three-point bend specimens with three different initial notch lengths under static and cyclic loading. The results indicate that GPC demonstrates superior fracture and fatigue performance, withstanding more load cycles than PCC. The analysis reveals that the crack growth coefficient $C$ of the size adjusted Paris’ law for GPC is significantly lower than that of PCC. However, both materials exhibit a similar crack growth exponent $m$. Microstructural analysis suggests that GPC’s enhanced fracture and fatigue performance is linked to its spheroidal globular type three dimensional microstructure and its elemental composition. Statistical analysis further confirms the superior performance of GPC over PCC at different stages of crack growth, with its variability best captured by log-uniform distribution in monotonic loading and Beta distribution in cyclic loading. Furthermore, the application of a predictive boundary effect method (BEM) confirmed the existence of a size effect in GPC. The findings of this study suggest that GPC could serve as a more durable and sustainable material for transit infrastructure such as roads, bridges, and rail sleepers subjected to cyclic loads.