Comparison of the air voids characteristics of different hot mix asphalt (HMA) mixture types
Academic Article
Overview
Identity
Additional Document Info
Other
View All
Overview
abstract
The internal structure of the hot mix asphalt (HMA) mixtures plays an important role in the response and performance of these paving mixtures. The objective of this paper is to conduct a quantitative comparison of the differences in internal structure -evaluated in terms of the air voids (AV) characteristics-of four HMA mixture types. Although the performance assessment of the HMA mixtures analyzed is out of the scope of this paper, the comparison conducted is useful to improve the understanding of the differences exhibited, at the macroscopic level, by different HMA mixture types. The AV characteristics (i.e., content, distribution, and size) were computed based on analysis of X-ray Computed Tomography images obtained from specimens compacted using the Superpave gyratory compactor (SGC). Corresponding results and analysis suggested that the mixtures studied presented irregular vertical distributions of total AV content and AV size, with a degree of heterogeneity that is mixture dependent, but not specimen dependent. Consequently, the specific laboratory procedure used to obtain SGC compacted specimens should be designed based on both the specimen height and mixture type. In addition, the comparative analysis also indicated that the mixtures considered as "difficult to handle" in the laboratory (i.e., PFC mixtures fabricated with asphalt rubber) did not exhibit the highest degree of heterogeneity in their internal structure. This conclusion suggests the need for proper handling of all types of HMA mixtures to get true replicate specimens.
