Abstract
This study presents a modified compaction concept of asphalt mixtures based on aggregate frictional behavior using self-developed image processing for measuring the aggregate orientation. The compaction energy index was introduced to evaluate the aggregate orientation on different compaction temperatures. For the better rearrangement of aggregates, there was an optimum temperature at which a preferred orientation exists, providing lower compaction efforts. An excessively high temperature reduced the asphalt contents for lubrication and caused additional aggregate friction to require higher compaction efforts. This phenomenon can be found in the changes of the volume of the effective asphalt binder (Veac) and the absorbed asphalt binder (Pba). The mixture produced higher Veac, at which an optimum compaction temperature required lower compaction energy. Despite being higher than the optimum temperature for the PG62-28 mixture, the Veac decreased by 0.4%. An increase of 0.35% in the Pba was inferred to flow into the aggregates. Clearly, a reduction of lubricant in the mixture caused a higher frictional interaction between aggregates. Changes in the Veac and the Pba can eliminate the viscosity effect for the rearrangement of aggregates. Based on the aggregate orientation and change in mixture volumetrics, the aggregate interaction effect was introduced to the Mohr–Coulomb compaction theory to explain the additional friction.
Highlights
There is overwhelming evidence regarding the significance of the fabric of asphalt mixtures, which is referred to as the internal structure of asphalt mixtures, on the compaction of asphalt pavements.With respect to material properties, the internal structure of asphalt mixtures is influenced by asphalt binder type, aggregate gradation, and aggregate shape/texture [1,2,3,4,5,6,7,8,9,10,11,12]
The compaction behavior of asphalt mixtures can be represented by the vector magnitudes (∆) as a parameter of aggregate orientation
Aggregate orientation is well-known as a good representative to reflect the shear resistance and stiffness of asphalt mixtures against compaction
Summary
There is overwhelming evidence regarding the significance of the fabric of asphalt mixtures, which is referred to as the internal structure of asphalt mixtures, on the compaction of asphalt pavements.With respect to material properties, the internal structure of asphalt mixtures is influenced by asphalt binder type, aggregate gradation, and aggregate shape/texture [1,2,3,4,5,6,7,8,9,10,11,12]. There is overwhelming evidence regarding the significance of the fabric of asphalt mixtures, which is referred to as the internal structure of asphalt mixtures, on the compaction of asphalt pavements. The importance of internal structure in asphalt mixtures has been recognized by experimental researchers in that the internal structure of an asphalt mixture affects the compaction performance and the pavement performance and distresses such as rutting, fatigue, and thermal cracking [18,19,20,21,22,23,24,25]. As a part of the Strategic Highway Research Program (SHRP) study for a new asphalt mixture design, the adoption of the Superpave Gyratory Compaction (SGC) method, which is a convenient way of assessing the compaction process of asphalt mixtures, shows pavement technologists to volumetrically characterize asphalt mixtures and its constituents on a more rational basis [26,27,28].
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