Gradation design of cement-stabilized macadam with large-stone skeleton using the multi-point supporting principle: performance evaluation and mechanistic analysis

The LSS-CSM consists of a large-sized stone (LSS) skeleton whose voids are filled with cement-stabilized macadam (CSM). Despite favourable anti-cracking performance, its standardized application is restricted by insufficient theories for determining the nominal maximum size (NMS) of CSM filler and the LSS/CSM mass ratio. This work extends the volumetric design method based on multi-point supporting skeleton (VDMPSS) to LSS-CSM design. Filling tests and penetration resistance analysis identify key gradation parameters and the optimal CSM filler NMS of 16 mm. The VDMPSS-optimized mixtures achieve 5.4% higher 7-day compressive strength (3.68 vs. 3.49 MPa) and 5.9% higher 28-day strength (5.77 vs. 5.45 MPa, p < 0.001), together with a 7.5% lower 60-day drying shrinkage strain (368 vs. 398 µϵ). Microscopic observations further confirm a denser and more continuous interfacial transition zone (ITZ) between the LSS skeleton and filling matrix. This research provides theoretical support for standardized design and engineering implementation of LSS-CSM.