Mechanical evaluation of asphalt–aggregate mixtures prepared with fly ash as a filler replacement

Abstract

The objective of this study is to investigate the effect of fly ash as a filler replacement on the mechanical properties of asphalt–aggregate mixtures. Utilization of fly ash, which is the by-product of coal-fired power generation, is of great importance from an environmental and economical point of view. In this study, a dense bituminous mixture composed of calcareous aggregate was selected as the reference mixture. It was observed that there was a definite increase in Marshall stability and decrease in flow values, especially when calcareous filler was replaced by Soma-type fly ash, which was one of the three types of fly ashes used. The mechanical properties, namely elastic strain, elastic modulus, and permanent strain, of the asphalt mixtures were determined by carrying out fatigue tests with a UMATTA tester for three types of fly ashes, portland cement, lime, and control specimens. The changes in mechanical properties are important in the sense that they affect the behavior of asphalt concrete pavement under applied loads. This mechanism can be explained basically by bitumen extension. The fatigue life of fly ash specimens, especially Soma fly ash, was found to be considerably higher than that of calcareous filler specimens. Based on this study, it is demonstrated that fly ash can be used effectively in a dense-graded wearing course as a filler replacement.