Mechanistic prediction of rutting in LSAM-50 flexible base pavements: a novel master curve model incorporating temperature and load effects

Permanent deformation (rutting) threatens the structural integrity and service life of asphalt pavements. This study investigated the rutting resistance mechanisms of flexible base pavements incorporating LSAM-50, an ultra-large stone asphalt mixture (nominal maximum aggregate size 53 mm), and developed predictive rutting models. Effects of aggregate gradation, binder type, and temperature were analyzed via shear strength theory, using cohesion c and the internal friction angle φ. Compared with conventional mixtures, LSAM-50 exhibited an approximately 10° higher φ and stronger aggregate interlock, and dynamic stability over 2.7 times that of finer-graded materials. A statistical regression model (SR-DS) with correlation coefficient above 0.95 was established. A rutting-depth master curve method was developed based on time–temperature equivalence, using shift factors to consolidate rutting data onto a reference condition, achieving R 2 > 0.92 and MSE < 0.01. Field measurements confirmed that LSAM-50 flexible base pavements exhibit deflection comparable to semi-rigid base pavements at room temperature, with fewer layers, faster construction, and over 30% material savings. With asphalt layer thicknesses of 42–54 cm, the LSAM-50 pavement system is consistent with perpetual pavement design principles. This study provides a mechanistic understanding and predictive tools for designing durable and rutting-resistant asphalt pavement structures.