Mechanism of low-temperature adhesion failure in asphalt mixtures with dense-suspension and void-skeleton structures

The low-temperature failure mechanism of mineral adhesion in asphalt mixtures with dense-suspension and void-skeleton gradations was investigated. Cylindrical-shaped minerals 60 mm in diameter and 55 mm high were split and then formed uneven surfaces that represented the amplified micro-surfaces of minerals. Based on the adhesion method of minerals in dense-suspension and void-skeleton structures, asphalt mineral powder sol slurry and a combination of fine aggregates were used to bond the specimen. Splitting tests were performed on the specimens at −30 °C. The splitting strength was tested and the adhesion failure zone on the interface of damage was analyzed. Main and secondary adhesion zones were found to exist among the aggregates in the asphalt mixture with the dense-suspension structure. The adhesion failure among the aggregates simultaneously occurred in the secondary adhesion zone and in the combination body of the fine asphalt aggregates. There was no secondary adhesion zone in the asphalt mixture with the void-skeleton structure. The adhesion failure among aggregates occurred in the internal sol slurry of the asphalt mineral powder. At a low temperature, the adhesion failure zone of asphalt mixture aggregates had a close relationship with the type of mixture gradation. There were more adhesion failure zones in the asphalt mixture with the dense-suspension structure than in that with the void-skeleton structure. The lower splitting strength of the combination body of fine asphalt mineral powders may have caused the adhesion failure of the mineral aggregates.

► Adhesion failure at a low temperature does not occur in the main adhesion zones.
► Slurry has a significantly better adhesion effect than the combination.
► Adhesion failure in a void-skeleton mixture occurs in the slurry itself.
► Adhesion failure in dense-suspension mixture occurs mainly in combination itself.
► Failure in dense-suspension mixture also occurs in secondary adhesion zones.