Comparative evaluation of crushing methods on the deagglomeration and enhanced properties of reclaimed asphalt pavement

Crushing treatment is essential for improving reclaimed asphalt pavement (RAP) quality, but how different crushing mechanisms affect aggregate-scale properties remains poorly quantified. Four crushing methods, namely small mesh hammer crushing, hammer crushing, jaw crushing, and double roller crushing, were compared in terms of deagglomeration efficiency and aggregate property enhancement. The residual mass ratio and physical and mechanical properties, including water absorption, crushing value, abrasion value, and needle and flake particle content, were evaluated. The surface micromorphology and roughness of RAP aggregates were examined using scanning electron microscopy (SEM) and 3D laser scanning. Small mesh hammer crushing achieved the highest deagglomeration efficiency, with residual mass ratios of 77.8%–96.6%. Hammer crushing reduced crushing and abrasion values by 6.14% and 23.87%, respectively. Water absorption increased by up to 32.86% in coarse fractions but remained within technical limits. Regression analysis confirmed strong correlations (R² > 0.7) between the residual mass ratio and aggregate properties. These findings provide a mechanistic basis for selecting crushing methods to optimize RAP quality for highway base applications.