Mechanical properties and energy evolution of coal gangue under multi-stage loading rates

This study investigates the mechanical behavior and energy characteristics of coal gangue for CO2 mineralization applications through x-ray diffraction (XRD) analysis, uniaxial compression tests, and cyclic compression testing. Key findings demonstrate the following. (1) Quartz and feldspar dominance endows coal gangue with high strength and exceptional elastic energy storage capacity. (2) The loading rate elevation enhances the mechanical performance, with the UCS and elastic modulus increasing by 20.85% and 27.6%, respectively, across 0.2–0.6 MPa/s range, whereas the peak strain decreases by 5.79%, indicating progressive embrittlement. (3) Under cyclic loading–unloading conditions, the elastic energy proportion in coal gangue specimens follows a declining-then-rising pattern in response to elevated loading rates, whereas the dissipated energy proportion displays an inversely correlated relationship. This observation implies that heightened loading rates suppress energy dissipation mechanisms, preferentially directing energy conversion toward elastic deformation pathways. (4) Under low loading rates, coal gangue specimens exhibit shear-dominated fracture patterns, whereas high loading rates lead to fragmentation failure with increased morphological complexity. These findings establish the crucial role of loading rate in controlling the energy distribution and failure mechanisms, providing fundamental guidance for optimizing comminution processes in carbon sequestration technologies.