Effects of Crushing Methods on Particle Morphology and Microcrack Damage of Moderately Weathered Rock Aggregates

Moderately weathered rocks contain primary fissures and mineralogical heterogeneity, making them susceptible to over-crushing and secondary microcracking during manufactured aggregate production. This study aimed to evaluate how different crushing methods affect particle morphology, fines generation, mechanical response, apparent porosity, and surface microcrack characteristics of moderately weathered rock aggregates. Feed and product samples from six field crushing operations, including double-roll, column-type, impact, hammer, vertical shaft impact (VSI), and cone crushers, were examined using particle-size analysis, flaky and elongated particle content, stone powder content, crushing value, apparent porosity, SEM observation, and image analysis. The column-type crusher showed the strongest fine-crushing effect, with a crushing ratio of 4.46, a −2.36 mm fraction of 96.15%, and stone powder content of 25.14%. Impact and hammer crushing were effective for coarse-size reduction but increased stone powder contents to 3.22% and 6.29%, respectively. In contrast, VSI crushing generated lower stone powder content (2.03%), limited apparent porosity increase (11.36%), and reduced crushing value to 3.91%, while improving particle shape. These results provide field-based guidance for low-damage crushing and process optimization of moderately weathered rock aggregates.