Trr No. 1323 Materials And Construction, pp. 123-133 Fillers added to asphalt concrete mixes have long been used as stiffening, extending, or otherwise void-filling materials, depending on their type and particle size. Fly ash, a by-product of the coal burning process for power generation, is a filler that can serve one or more of the above-mentioned functions. The role of fly ash in asphalt c…