Maximum aggregate size effects on fracture parameters and crack extensions in recycled aggregate concrete: Experimental and predictions

Abstract The use of recycled aggregates in concrete can lead to structural differences, which in turn affect its fracture behavior. These differences are expected to influence crack propagation and fracture parameters. Therefore, investigating the crack behavior of recycled aggregate concrete (RAC) and applying fracture mechanics, which examines crack initiation and propagation, is essential. This study aims to evaluate the effect of maximum aggregate size ( d max = 9.5, 12.5, 19 mm) at two water‐to‐cement ratios ( w/c = 0.35, 0.5) on the fracture parameters and ductility of RAC using the boundary effect method (BEM). Experiments were conducted on 72 notched beams under a controlled testing system using the three‐point bending test method. Results show that the size‐independent fracture energy ( G F ), initial fracture energy ( G f ), and fracture toughness ( K IC ) obtained from BEM improved by approximately 31.91%, 33.68%, and 25.51%, respectively, as d max increased from 9.5 to 19 mm. Furthermore, the reference crack length parameter () indicates that with increasing d max at both w/c levels, the concrete becomes more ductile, and its design criterion aligns with strength‐based criteria. The value of for RACs increases by approximately 42.11% and 24.36% at w/c ratios of 0.35 and 0.5, respectively, as d max increases from 9.5 to 19 mm. On average, the ratio of G F / G f obtained from BEM for RAC with different d max at both w/c levels was 3.84. Finally, the obtained mechanical properties and test variables were used to develop multivariate predictive models for RAC fracture parameters with varying d max . A comparison between the experimental results of this study and those of other researchers showed acceptable accuracy.