Influence of the Aggregate and Specimen Size on the Tensile Behavior of Notched Concrete Beams under Varying Strength Grades
Résumé
The influence of specimen size and maximum aggregate size on the tensile strength of notched C25, C45, and C60 grade concrete beams is investigated. Concrete beams with maximum aggregate sizes of 16 mm and 25 mm were subjected to three-point bending tests using three sample sizes (D1: 100 × 400 × 1200 mm, D2: 100 × 200 × 600 mm, D3: 100 × 100 × 300 mm). The results demonstrated that smaller specimens (D3) consistently exhibited higher tensile strengths than larger specimens (D1), with tensile strength increasing from 26% to 90% as specimen size decreased. The size effect was most pronounced in lower-grade concrete (C25) and diminished in higher-grade concrete (C60) due to enhanced fracture resistance and reduced sensitivity to microcracking. Smaller aggregates (16 mm) outperformed larger aggregates (25 mm) in tensile strength with a notable 17% improvement in D3 samples of C25 concrete. Conversely, larger aggregates demonstrated superior performance in larger C45 and C60 specimens due to their enhanced crack-bridging capacity. The interaction between specimen size and aggregate size highlights the importance of homogeneity and interfacial bonding in smaller specimens, whereas the crack-bridging ability of larger aggregates becomes more critical in larger specimens. These findings align with established fracture mechanics principles and underscore the necessity of considering size and aggregate effects in concrete design and testing to ensure accurate structural performance and reliability.
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