The effect of incorporating magnetic fly ash in asphalt binders with respect to permanent deformation and fatigue

Abstract

The search for efficient and environmentally viable materials to improve the quality and durability of asphalt binders used in roadways has been growing in recent years. This is especially true giving the increase in the volume and magnitude of traffic loads, as well as the changes in the earth's temperature that cause frequent pavement distresses, such as permanent deformation and fatigue. In this context, the objective of this work is to evaluate the potential of magnetic particles from fly ash, as a residual resource with high added value and low-cost raw material for modifying asphalt binders. Magnetic particles were incorporated into the asphalt binder at 2%, 4%, 6% and 8%, content by weight. The materials were characterized by chemical, empirical and rheological tests, specifically the Multiple Stress Creep and Recovery and the Linear Amplitude Sweep test. X-ray Fluorescence data revealed silicon, aluminum and iron as the main elements present in the fly ash, as well as the increase in iron concentration after magnetic separation in the magnetic particle sample. A homogeneous dispersion of magnetic particles in the asphalt binder observed by Scanning Electron Microscopy and shifts in infrared bands characteristic of iron (ca. 450 cm-1) and of asphalt binder (ca. 1456 cm-1) clearly indicated a significative interaction between the magnetic particles and the asphalt binder. The rheological results indicated that the incorporation of particles provide better performance to the binder in terms of both permanent deformation and fatigue. The modified binders were less susceptible to permanent deformation than the neat binder, and this is reflected in the increase in adequate traffic levels, moving from standard traffic to heavy traffic at a temperature of 64 °C. This economical, easy, and sustainable approach to using magnetic particles in hot asphalt binders can contribute to producing asphalts that are more efficient with changes in temperature and traffic.