The dynamic mechanical properties of dam concrete play a critical role in the seismic design of dams. Conducting experiments on large-scale fully graded specimens to accurately obtain the mechanical properties of dam concrete is a challenging task. Dam concrete performance is typically evaluated using standard-sized wet-screened specimens. Therefore, it is essential to understand the relationship between the mechanical properties of fully graded and wet-screened specimens under dynamic loading; however, research in this field is scarce. This study investigated the dynamic flexural and compression tests of fully graded and wet-screened dam concrete specimens under strain rates corresponding to seismic loading. The strain rates for the flexural tests were set to 10⁻⁶ s⁻¹, 2 × 10⁻⁴ s⁻¹, 8 × 10⁻⁴ s⁻¹, and 3 × 10⁻³ s⁻¹, while the strain rates for the compression tests were set to 10⁻⁶ s⁻¹, 5 × 10⁻⁴ s⁻¹, 8 × 10⁻³ s⁻¹, and 2 × 10⁻² s⁻¹. Failure modes and strain–stress curves were obtained for various strain rates. Based on the experimental data, the strength, elastic modulus, crack propagation velocity, cracking stress, cracking strain, peak compressive strain, and compressive energy absorption capacity of dam concrete under dynamic strain rates corresponding to seismic loading were determined. The effects of strain rate on these mechanical properties of dam concrete were analyzed. The relationship between fully graded and wet-screened concrete was explored, leading to a linear empirical formula for predicting the strength and elastic modulus of dam concrete based on wet-screened concrete test data. This study enriches the experimental research on the mechanical properties of dam concrete, deepens the understanding of the relationship between fully graded and wet-screened specimens, and provides scientific experimental data to support the seismic safety design of dams.

Tensile behavior governs the seismic safety of high concrete dams. This study integrates testing with mesoscale simulation to elucidate the tensile-failure mechanisms of dam fully graded concrete. Uniaxial tension, splitting tension, and flexural tests were performed on 450 mm-scale specimens using a 15 MN servo-hydraulic system. A two-dimensional random-aggregate model was then developed with globally inserted cohesive interfaces, and parameters were calibrated against the tests. Across ten random aggregate mesoscale models per loading case, simulations reproduced the measured responses. Predicted failure patterns matched observations, with cracks initiating along interfacial transition zones (ITZs), linking through mortar, and forming through-cracks. Quantified damage evolution revealed three stages—elastic response, ITZ crack initiation and extension, and mortar penetration—with >80% of cumulative damage localized in ITZs. One-at-a-time sensitivity analyses showed that (i) mortar tensile strength primarily controls peak strength but increases brittleness; (ii) ITZ tensile strength governs crack-initiation stress, ITZ shear strength shapes splitting-failure mode, and fracture energies mainly delay post-peak softening; and (iii) aggregate parameters exert comparatively weak influence on macroscopic behavior. The combined experimental–mesoscale framework provides mechanism-based guidance for selecting material parameters in seismic analyses, supporting performance-informed design and assessment of high dams.