Criterion to Select the Maximum Aggregate Size of Fine-Aggregate Asphalt Matrices

Fine-aggregate matrices (FAMs) are a relevant constituent of asphalt mixtures. Several FAM mix design, fabrication, and characterization protocols have been recently developed to investigate the behavior of such materials. However, there is a lack of experimental evidence on how to define the most appropriate maximum aggregate size (MAS) to fabricate FAM specimens. The focus of this paper is to develop such experimental evidence. Three asphalt concretes (ACs) and their corresponding FAMs with different MASs were tested to determine their stiffness and fatigue properties in uniaxial cyclic tests. In addition, the AC microstructures were scanned using X-ray micro-computed tomography (micro-CT) and analyzed using image analysis techniques. The combination of the AC microstructure assessed by micro-CT with the mechanical characteristics of the mixtures allowed the determination of the most representative MASs for the fabrication of isolated FAM samples. The key conclusion from this study was that ACs with nominal maximum aggregate sizes of 19.0, 12.5, and 9.5 mm are better characterized by FAMs with a MAS of 2.36 mm.