Fly ash has been effectively used in concrete; however, there are limited applications in which fly ash has been used in asphalt pavements. The reported research demonstrates that the use of fly ash in bitumen materials is an attractive option because it improves performance and reduces costs and environmental impacts. Microstructural investigation demonstrated that the crack-arresting was induced by the fly ash particles evenly distributed within bitumen matrix. To assess the effect of fly ash on the rheological performance of asphalt cement, a dynamic shear rheometer was used to measure the binder's resistance to shear deformation in the linear viscoelastic region. The rutting factor, G*/ sin(delta) and dynamic viscosity, eta', were determined for different types of bitumen at different temperatures, with 5%, 15%, 30% and 60% of binder replacement by weight of fly ash class C and F. The addition of fly ash improved the rutting factor and reached a higher performance grade of the binders. The viscosity for both bitumen types increased at 124 degrees C degrees, but for the most of the compositions it remained within the range for mixing and placement of asphalt concrete. (C) 2013 Elsevier Ltd. All rights reserved.