Using Fly Ash as a Filler Replacing Agent and the Mechanical Evaluation of Dense Bituminous Mixtures by Repeated Load Indirect Tensile Tests

In this study, it is aimed to explore the outcome of fly ash as a filler replacing agent on the mechanical properties of dense bituminous mixtures prepared by utilizing calcareous filler as control specimens. Fly ash, which is the by-product of coal fired power generation, and mainly defined as a waste material, is of great importance from the economical and environmental point of view in pavement engineering. In this study, a dense bituminous mixture was selected as reference mixture, composed of calcareous aggregate. It was observed that there was a definite increase in Marshall stability and decrease in flow values when calcareous filler was replaced by different types of fly ashes, Portland cement and lime. Moreover the mechanical properties, namely elastic modulus, elastic strain and permanent strain of the dense bituminous mixtures were termined by carrying out repeated load indirect tensile tests with UMATTA tester for three types of fly ashes, Portland cement, lime and control specimens. The change in the mechanical properties are important in the sense that they affect the asphalt concrete pavement behaviour under applied loads and this mechanism can be explained basically by bitumen extension which is the main cause of the increase in stiffness values of dense bituminous mixtures. The fatigue life of fly ash specimens, especially Soma fly ash, was found to be considerably higher than control specimens. Based on this rationale, it is demonstrated that fly ash can be used effectively in a dense graded wearing course as a filler replacing agent and this results in great economy and shows another application area of fly ash other than concrete engineering which results in improved asphalt aggregate mixture properties which is very important from soundness of the flexible pavements.

Keywords:

fly ash , filler replacement , Marshall stability , flow , mechanical properties , repeated load indirect tensile test , bitumen extension , fatigue life