Properties of Fillers: Relationship with Laboratory Performance in Hot Mix Asphalt

The work presented in this paper describes the research activities of the task group 'Properties of filler aggregates' which was conducted recently at the Belgian Road Research Centre (BRRC). The main objectives of the task group included the investigation of the characteristics of the filler aggregates, the requirements to be met by fillers, and the possible introduction of test methods capable of ensuring a constant quality and performance of fillers in hot mix asphalt. In a first step of the study, the properties of a large number of filler aggregates obtained by processing natural and/or manufactured or recycled materials were assessed, yielding important information about the constancy or possible variability of characteristics over a production period of about two months. During this initial phase, research concentrated on filler properties linked to specifications in the European standard EN 13043. Subsequently, following the manufacture of mastics, the stiffening properties of fillers were investigated by determining the "Delta Ring and Ball" softening temperature and the mastic viscosity at 60 C by DSR. It was anticipated that latter test results could provide useful information with respect to filler performance in an asphalt mix. Finally, the possible impact of filler materials on the performance of asphalt mixes was explored by measuring the Marshall characteristics of an AC-14 binder course. Moreover, the water sensitivity of latter asphalt mixes was evaluated by a series of retained Marshall experiments.