Research on Strongly Skeleton-Interlocked Gradation of LSAM-50 Mixture Based on Interlock-Dense Theory

Large stone asphalt mixture (LSAM) base layers for pavements demonstrate outstanding rutting resistance and lower engineering costs, potentially mitigating the structural damage often observed in traditional flexible base layer asphalt pavements. Drawing upon the interlock-dense theory and the variable I method, this study proposes optimal gradations for coarse and fine aggregates; it also suggests an optimal mortar dosage through exploring the impact of asphalt mortar dosage on the mixture’s mechanical properties. Further, the study optimizes the sensitivity of the coarse aggregate mass fraction to the mechanical indices of the mixture to refine the critical sieve size. Eventually, LSAM-50 with strongly skeleton-interlocked gradation was proposed, and a test road was paved to verify its performance. Results indicate that continuous grading significantly improves mechanical properties. Specifically, the mineral grading for LSAM-50 is set as S1∶S2∶S4=5∶2∶3, and S6∶S5=3∶1, with a fine aggregate grading reduction coefficient i of 0.75, and an asphalt mortar dosage of Mj+3%. Compared to traditional asphalt base course mixes, LSAM-50 significantly enhances compressive strength (CS) by at least 37%, splitting strength (SS) by at least 13%, and high temperature performance by over 400%. Both the test road surface and the coarse aggregates in the core samples exhibit a cohesive, strongly integrated dense skeleton structure.