Rolling friction and particle shape as controls on the static angle of repose of a recycled granular sub-base material

Recycled concrete aggregate is the most direct route to reusing construction and demolition waste as structural sub-base fill, yet its DEM contact parameters remain unconstrained. This study verifies a static angle-of-repose pipeline for ATAIR-EDEM framework material M6 and quantifies three controls on the simulated angle. A funnel-pour deck (1,500 particles, Hertz–Mindlin no-slip with constant-torque rolling friction) was authored from first principles in EDEM 2024; the angle was fitted by least squares to radial-bin surface heights across eight azimuthal sectors inside a 120 mm analysis domain. The verified baseline gives δ = 12.53° ± 0.88° (CV 7.1%). Raising rolling friction from 0.12/0.01 to 0.30/0.35 (RCA–RCA/RCA–steel) moved δ to 26.73°, at least seven times the between-pour standard deviation measured across independently seeded pours (0.60°, n = 3; 0.80°, n = 2). Replacing the near-spherical three-sphere clump with a five-sphere angular template added 3.66° at High friction, replicated to a between-pour SD of 0.08°. A + 0.25 static-friction increment moved the pooled result by 0.92–1.21°, the smallest of the three effects and contrary to the ranking reported for cylindrical-discharge geometry. At least 16° of the gap to the 47° measured recycled-aggregate benchmark stays unclosed. This is a verification and sensitivity study for M6, not a completed calibration.