Meso-scale study on compaction characteristics of asphalt mixtures in Superpave gyratory compaction using SmartRock sensors

Abstract

Compaction degree is an essential parameter to characterize the construction quality and performance of asphalt pavement. Under the same compaction conditions, asphalt mixtures with different aggregate sizes and gradation may exhibit different compaction characteristics. Accordingly, this paper aims to study the compaction characteristics of asphalt mixture at the meso-scale through particle response of the mixture by using SmartRock sensor. Firstly, a laboratory test scheme of the asphalt mixture is designed and the SmartRock sensors are used to obtain the internal stress of the mixture during compaction. By comparing the particle stress with the height of the specimen, it is inferred that the stress state of the particles can reflect the compactness of the compacted material, and the change rate of compaction degree in logarithmic coordinates is proposed to characterize the compaction performance of the asphalt mixture. Furthermore, the quantitative analysis is comprehensively conducted related to the different nominal maximum aggregate size (NMAS), locations and gradation types. The results reveal that the asphalt mixture with larger NMAS has a better compactibility in terms of forming a stable skeleton structure, and the mixture in the middle of specimen can be compacted more easily than that in the top and bottom area of specimen. It can be aslo found that the gradation type affects the compaction performance through the probability of coarse aggregates interlocking with each other. The open-graded mixture (i.e, PAC-16) is relatively faster to achieve the target compaction degree than gap-graded and dense-graded mixtures (i.e, SMA-16 and AC-16, respectively). Although the asphalt mixture with larger NMAS and coarser gradation can reach a certain compaction degree with a rapid speed, it doesn't mean the mixture can achieve higher compaction degree finally under the action of subsequent compaction work. The test result shows that the asphalt mixture with coarser aggreages is relatively difficult to compact with lower final compactness. The experimental research sheds substantial light on the internal relationships between the response of the particles and compaction charateristics of asphalt mixture at meso-scale.