Experimental and Numerical Assessment of Structure and Coarse Aggregate Size Effects on the Mechanical Properties of Concrete

ABSTRACT This study investigates the influence of cylindrical specimen size and coarse aggregate size on the mechanical properties of concrete by testing samples of proportionally varying dimensions across three concrete grades (C25, C45, and C60) with two maximum aggregate sizes (16 and 25 mm) under static loading. Additionally, a mesoscale numerical study was conducted to assess structural size effects, aggregate size effects, and failure mechanisms. The findings confirm a significant size effect, with compressive strength reductions ranging from 51.54% to 56.42% as specimen dimensions increase. Lower‐strength concrete (C25) exhibited greater susceptibility to this effect, while high‐strength concrete (C60) displayed improved resistance. The modulus of elasticity also declined substantially, with reductions reaching 30.5%, particularly in mixes with larger aggregates. Poisson's ratio exhibited minor variations, slightly increasing with specimen size (0.15–0.25), indicating higher lateral deformation in larger samples. Smaller aggregates enhanced compressive strength and stiffness, improving performance by up to 10% in high‐strength mixes, while their effect on Poisson's ratio was negligible. Numerical simulations at mesoscale validated these experimental trends, revealing that larger specimens exhibit more complex crack propagation and lower strength retention. Compared with previous studies that examined smaller specimens, this study extends the analysis, revealing greater strength reductions at larger scales.