Manufacturing reclaimed asphalt test specimens using gyratory compactor

Abstract

This paper presents a laboratory investigation aiming to provide a protocol that allows to confidently using gyratory compaction for the production of reclaimed asphalt test specimens. The presented investigation is part of a wider experimental programme aiming at obtaining input parameters for modelling purposes. For this reason, it has been necessary to define a quick and reliable and repeatable procedure to manufacture a high number of specimens with a limited amount of material. Gyratory specimens were compacted by targeting to densities defined in previous Marshall mix design and with the final aim of obtaining specimens with a fixed and homogeneous distribution of air voids content. The study has been developed by comparing results of two Stone Mastic Asphalt mixtures, a control mix with virgin material and a reclaimed asphalt mix with 30% of RA. The mixtures had almost identical air void contents, aggregate grading curves and the binders had similar conventional binder properties. Homogeneity of air void distribution was investigated by X-ray Computed Tomography (CT), image analysis techniques and buoyancy tests. Coring and trimming of the compacted specimens were used to obtain the final test specimens with fixed homogeneous properties. The study concluded that gyratory compaction is suitable to produce homogeneous test specimens also for mixtures containing high amount of reclaimed asphalt. Nevertheless final coring and trimming of the specimens are mandatory as well as performing a preliminary investigation for each material consisting in the compaction, and the further buoyancy tests, of few specimens having densities ranging from 100 to 90% of the initial target. The presence of high percentage of RA did not present remarkable issues apart making the compaction harder. This study has been developed within the FP7 European Project Re-Road.