Impact Dynamic Characteristics and Damage Features of Early-Age Concrete-Mudstone Composite

To investigate the dynamic mechanical properties of early-age concrete-mudstone composites under impact loading, split Hopkinson pressure bar (SHPB) tests integrated with a high-speed camera were conducted on composite specimens with curing ages of 1, 3, and 7 d. Digital image correlation (DIC) technology was employed to analyze the evolution of displacement and strain fields, systematically revealing the dynamic damage and failure characteristics of the composites. The test results indicate that as the strain rate increases, the composite specimens exhibit significant strain rate dependence across all curing ages, and their dynamic strength growth follows a logarithmic function model. The energy dissipation density increases linearly with incident energy. DIC measurements show that the maximum surface displacements of the 1, 3, and 7 d specimens are 1.564, 1.196, and 0.924 mm, respectively, with corresponding maximum strains of 1.886%, 1.352%, and 1.184%. This study elucidates the dynamic mechanical behavior and damage-failure mechanisms of early-age concrete-mudstone composites under impact loading, providing a theoretical foundation for damage prevention and control in surrounding rock-initial support structures during tunnel blasting construction.