Development of morphological properties of road surfacing aggregates during the polishing process

This study investigated the morphological properties of different road surfacing aggregates. Eleven types of aggregates with great variances in their mineralogical properties were chosen for the study. For each type, 500-gram test samples were prepared and subjected to polishing using the Micro-Deval (MD) apparatus. Before and after polishing, 48 particles from each type of aggregate were selected and run through the aggregate imaging system and X-ray computed tomography equipment to capture the change of morphological characteristics, including sphericity, angularity and texture. The results showed that log-normal functions are ideally suited to describe distributions of the analysed morphological characteristics before and after MD. The mass loss of each aggregate can be well described with a function using the expected value of morphological parameters with the aid of a multiple regression analysis. The change of angularity is the main cause for the mass loss whilst the changes of both the sphericity and texture only have an ancillary influence.