Influence of concentration and packing of filler particles on the stiffening effect and shearing behaviour of asphalt mastic

[Display omitted] •This paper evaluates lime kiln dust and dolomite powder as mineral fillers in asphalt mastic.•Differences in asphalt and filler properties causes changes in asphalt to particle interaction.•Thus, leads to differences in particle settlement, diffusion, energy dissipation and suspension rheology.•Incorporation of fillers with different properties and concentrations affects mastic behaviour.•Moreover, affect its performance predictability. The experimental investigation of the effects of filler-bitumen interaction on the stiffening and shearing characteristics of asphalt mastic is presented in this paper. The role of filler particles in terms of particle dispersion, particle sedimentation rate, particle dissipation energy, and their shearing response as a function of their viscosities under different concentrations was analysed. Structural and geometrical morphological tests of the filler particles were also carried out using the Scanning Electron Microscope (SEM) analysis. A neat bitumen of 60/70 penetration grade and two alternative mineral fillers, namely lime kiln dust (LKD) and dolomite powder (DP), were used to produce asphalt mastic mixture at a filler- bitumen ratio (F/B) of 0.4, 0.8, and 1.2 in accordance with the Superpave mix design dust to binder ratio specification. The two individual fillers particle size gradations, was assessed using a laser diffraction technique. The delta ring and ball, as well as the penetration index tests were conducted to determine the physical properties of the asphalt mastic. The shearing response of the asphalt mastic was also determined using a rotational viscometer (RV) device for various shear values at mastic mixing temperature. The results of the study inferred that the stiffening ability of mineral fillers was more dependent on the physical filler properties, such as particle surface area, voids between the interstices of particles, the concentration of particles, and the crowding distance of the particles in the asphalt mastic. It also revealed that the resistance of a neat bitumen to shearing occurs in a shear-thinning response behaviour, while that of an asphalt mastic occurs more as a shear thickening resistance response. The morphological analysis of both the fillers highlighted the differences in voids, fines, surface area, and particle shape structure of the two fillers.