Particle-size sensors of different geometry to assess the workability of asphalt mixtures

The compaction process of asphalt mixtures has a great influence on the durability and long-term performance of flexible pavements. To improve the field compaction process, particle-size sensors have recently been introduced and standardised to assess the workability of asphalt mixtures. Most studies employ cubic shell sensors or sensors with an irregular shape. Moreover, to date, no study has assessed whether the choice of the gyratory compactor can affect the sensor measurements. Within this context, the objective of this study is to compare particle-size sensors with easily reproducible shell geometries (cubic, spherical), in order to verify their behaviour during compaction and their ability to assess the workability of three asphalt mixtures with different characteristics. Moreover, the study compares two gyratory compactors with different compaction mechanisms to provide a preliminary analysis of the gyratory compactor influence. The results indicate that the spherical sensor can be more sensitive to workability variations. Furthermore, the cubic sensor may hinder compaction in the surrounding area by impeding the movement of the adjacent aggregates. The compaction mechanism, which can vary for different gyratory compactors, may have a certain influence on the compaction process. Finally, the ratio between the sensor size and the mixture nominal maximum aggregate size is an aspect to be taken into due consideration.