Characteristics of void distribution and aggregate degradation of asphalt mixture specimens compacted using field and laboratory methods

Abstract

Asphalt mixtures compacted in the field and in a laboratory show obvious differences in their internal structures, and this affects the evaluation of pavement performance. Hence, in this study, to find a laboratory compaction method most similar to the field method, the effect of the field method and multiple laboratory compaction methods on the internal structure of asphalt mixture specimens was investigated. First, based on the principle of keeping the same compaction degree, specimens cored from field specimens were prepared with six laboratory methods. Then X-ray computed tomography (X-ray CT) and digital image processing (DIP) technologies were used to analyze the internal structure of the specimens, including the spatial distribution and particle size of the voids, as well as the aggregate degradation. Finally, the similarity of the laboratory specimens to the field specimens was evaluated. The results indicated that the spatial distribution of the voids was affected by the compaction methods. The edge effect was different in specimens with different heights. The symmetry of the distribution curve of the air voids was affected by the distribution of the compaction effort. The void particles in a certain size range occupied most of the volume, and the size distribution of the void particles inside the specimens was affected by the compaction methods. In the compaction process of the static load method, the aggregates were constrained and seriously broken, while the dynamic load and the kneading action could protect aggregates from being broken. In general, the partial specimens compacted using a Superpave gyratory compactor (SGC) and a shear box compactor (SBC) were more similar to the field specimens than other laboratory specimens. This study offers a reliable basis for studying the internal structure of asphalt mixture specimens compacted using different methods and for guiding laboratory compaction based on the field method.