Effects of Filler Properties on the Rheological and Volumetric properties of Mastics and Asphalt Mixes

Abstract

This paper describes the effects of varying filler properties on the rheological properties of mastics and volumetric properties of asphalt mixtures. The main aim of the study was to evaluate how filler properties affect the rheological properties of the mastic that dictate asphalt performance (i.e. rutting, fatigue cracking and thermal cracking). An additional objective of the study was to evaluate some of the volumetric properties of the asphalt mixtures produced with the studied fillers, in particular to see how filler properties affect the compaction of asphalt mixtures.
The fillers used in this study were evaluated according to four common filler properties: Specific Surface Area (SSA), Rigden air voids, specific weight, and average particle size. The laboratory evaluation of the materials was divided into two main sections. First the four different mastics were prepared by blending filler and bitumen, subsequently rheological evaluations of these mastics were conducted using the Dynamic Shear Rheometer (DSR) and the Bending Beam Rheometer (BBR). Specifically, the performance grade (PG) of the mastics with regards to permanent deformation and cracking were evaluated. Next, asphalt mixtures were produced using the studied fillers to evaluate the volumetric properties of asphalt samples prepared with different filler types.
The results of the study indicate that the specific surface area of the filler is strongly correlated with permanent deformation susceptibility of the mortar. Whereby, increasing the specific surface area of the filler was seen to decrease the susceptibility of the pavement to permanent deformation. Weaker correlations were found for specific weight and average particle size for thermal cracking of asphalt pavements.
Some correlations were found linking the volumetric properties of the laboratory prepared asphalt samples with filler properties. However, in general these correlations were weaker than those between the mortar properties and the fillers. These findings suggest that some filler properties may affect asphalt pavement performance, whereby the largest effect is due to the modification of the bitumen due to the presence of the filler.