Fly ash as low cost and environmentally friendly filler and its effect on the properties of mix asphalt

Abstract

Abstract In the countries where the energy industry is based mainly on coal, the management of the waste generated in the process of its combustion (fly ash) is a serious problem. The article presents the properties of mix asphalt where the traditional limestone filler was replaced by fly ash in 25%, 50% and 75%. Two kinds of ashes were used for the tests: class F and class C; these ashes were characterized in terms of chemical composition, mineralogy and grain size. In total, the tests were carried out for 7 types of mix asphalt: reference AC 11 S and 6 mixes with lime-ash filler. Bulk density of an mix asphalt, maximum density of a mix, air voids content, indirect tensile strength and water and frost resistance for obtained mix asphalt were determined. For the samples with fly ash addition, the air voids ranged from 1.2% to 1.6% in the case of class F and from 1.3% to 2.8% in the case of class C fly ash. Water and frost resistance was 96%–104% and 102%–104%, respectively for the samples with the addition of class F and class C fly ash. The results indicate that both classes of fly ash can be applied as the alternative mineral filler, since the air voids as well as resistance to water and frost of the obtained mix asphalt met the standards.