Spatial and directional distribution of aggregates in asphalt mixes

This study presents experiments and analytical methods to capture and quantify the directional and spatial aggregate distributions in hot mix asphalt (HMA). The quantifying parameters were obtained by processing and analyzing images of HMA sections. An experimental technique in which HMA sections were treated with hydrofluoric acid was developed in order to improve the contrast between aggregates and asphalt prior to capturing an image. The developed methods were used to analyze the aggregate distribution in mixes compacted in the laboratory using the Superpave gyratory compactor (SGC) under different compaction variables, and in the field using different compaction patterns. The field cores exhibited similar aggregate distributions irrespective of the compaction pattern, whereas the angle of gyration and specimen height in the SGC were found to influence significantly the aggregate distribution. Laboratory specimens compacted to a height close to that of field cores, and using an angle of gyration of 1.25°, were better in simulating the aggregate distribution in the field.