Influence of fly ashes as alternative filler in asphalt mixtures

This study defined the mechanical/volumetric properties and the environmental compatibility of bituminous mixtures containing fly ashes as alternative of traditional limestone filler. The research study is articulated in different steps as follows: a) characterization of fly ashes according to UNI EN 1303 Standard; b) environmental compatibility analysis of mastics containing fly ashes by using a leaching test; c) stiffness evaluation of the mastics containing limestone and fly ash filler by static testing, as Delta Ring and Ball Test, and dynamic testing, as Frequency Sweep Test; d) mechanical and volumetric characterization of asphalt concrete containing fly ashes and limestone filler starting from a phase of mix design of hot mix asphalt mixtures. The characteristics of rigidity of the bituminous conglomerates has been evaluated using the HMA optimal mixture analysis through a dynamic test with a sinusoidal load. Then, the ability of two different HMA to endure a permanent deformation was evaluated by a Repeated Load Axial Test. The results has shown that mixtures of Hot Mix Asphalt with flying ashes as filler, compared to Hot Mix Asphalt containing limestone filler, is preferred in terms of mechanical performances and relevant environmental compatibility evaluated with a leaching test.