<p>Understanding the effects of weathering on the porous structure of ballast materials is crucial for optimizing their selection and application in various environmental conditions. However, limited research exists on the porosimetric behavior of ballast materials under accelerated weathering conditions. This study investigates the porosimetric behavior of LD steel slag, basalt, and gneiss under accelerated weathering conditions, simulating 75 freeze-thaw and 40 sulfate soundness cycles. The research employed X-ray microtomography (Micro-CT) to analyze the three-dimensional pore structure of the materials before and after weathering. Additionally, standard laboratory tests were conducted to determine specific gravity, water absorption, and apparent porosity. Results indicate that weathering significantly impacts the porous structure of all materials. Basalt exhibited increased susceptibility to chemical weathering, leading to a notable rise in open porosity. Gneiss demonstrated superior resistance to both weathering cycles, maintaining a stable pore structure. LD steel slag, however, proved highly vulnerable to physical weathering, experiencing significant increases in both open and closed porosity. These findings provide valuable insights into the long-term durability and performance of these materials as railway ballast.</p>