Use of modified oil fly ash to enhance asphalt concrete performance

Combustion of heavy fuel oil at power generation facilities and desalination plants produce large quantities of heavy oil fly ash (OFA). Waste ash production is expected to increase with the increasing use of heavy or cracked oil as fuel in inefficient power generation facilities. Oil ash can pose a health hazard by affecting the respiratory system and may contaminate the water table if improperly dumped. Utilization of the heavy oil ash in construction materials provides a viable use for this by-product, thereby protecting the environment and eliminating the need for building special disposal areas for the ash. In this study, three different chemical treatment methods were used for the surface modification of oil fly ash. Elemental analysis indicated that the treatment process removes some of the elements such as vanadium, iron, and nickel from the OFA samples. FTIR analysis shows that the main difference between the three treatment methods is the introduction of three different functional groups. Untreated and surface-modified oil fly ash were blended with asphalt binder at a ratio of 2 % and used in asphalt concrete mixes. Performance grade of ash modified asphalt binders increased from 64–16 to 76–16. Asphalt concrete mixes modified with chemically treated OFA has 11 % higher split tensile strength, 25 % higher resilient modulus, 1,400 % increase in fatigue life and 55 % reduction in rutting as compared to neat asphalt concrete mix treated with the same asphalt content. Modifying asphalt binder with 2 % of chemically treated OFA significantly improves the performance of the asphalt pavement.