Macroscopic and Microscopic Performance Study of Filling-Type Large-Size Cement-Stabilized Macadam

Filling-type large-size cement-stabilized macadam (F-LSBC) is a promising base material for mitigating reflection cracking in semi-rigid pavements. However, its engineering application is hindered by the challenge of balancing strength, crack resistance, and construction adaptability. More fundamentally, the relationship between micromechanical features-especially the interfacial transition zone (ITZ)-and the macroscopic behavior of filling-type cement-stabilized composites remains insufficiently understood. This study used conventional cement-stabilized macadam (CSM) as a reference and combined nanoindentation with macro-scale mechanical, fatigue, and drying shrinkage tests to clarify the micro-macro mechanisms of F-LSBC. Results show that the ITZ in F-LSBC exhibits substantially lower elastic modulus (reduced by 60-75%) and hardness (reduced by 55%), along with greater porosity and phase volume fraction than CSM. Cluster analysis revealed a thicker ITZ (55-90 μm vs. 40 μm), indicating notable interfacial weakening. These microstructural features lead to reduced strength and fatigue life. Nevertheless, due to its high coarse aggregate content and weak-interface-induced "crack-without-displacement" mechanism, F-LSBC demonstrates enhanced shrinkage resistance, with drying shrinkage reduced to 81.36% of that of CSM at 180 days. The findings emphasize the key role of ITZ characteristics in determining performance and suggest that improved interface engineering could enhance durability and shrinkage control in pavement bases.