Effect of Jordanian Oil Shale Fly Ash on Asphalt Mixes

Abstract

It is estimated that about 40 billion tons of oil shale is available in the southern part of Jordan. Several studies are being carried out to utilize this source of energy efficiently. Upon direct combustion of this oil shale, more than 50% of its quantity will be left as fly ash. Resulting fly ash is considered undesirable and environmentally hazardous. This investigation was conducted to make use of the fly ash in the modification of local asphalt mixes. The modification efficiency was evaluated by the improvement in the performance of prepared asphalt concrete mixes. To carry out this study, enough quantity of oil shale was collected from Al-Lajjoun quarries (about 100 km south of Amman, Jordan). This material was then crushed, sieved, and burned to obtain the fly ash. Chemical and physical analyses of the fly ash were then performed. Asphalt concrete mixes having different percentages of fly ash (0, 10, 50, and 100%) as a replacement of the mineral filler, material passing the 0.075 mm sieve, were prepared. These samples were characterized using the Marshall Stability, indirect tensile strength, stripping resistance, resilient modulus, dynamic creep, fatigue, and rutting tests. Test results were statistically analyzed and indicated that, in general, the addition of fly ash improved both strength, and water sensitivity of the asphalt concrete mixes. Replacing 10% of the mineral filler by fly ash proved to be the most effective percentage in improving the mechanical properties of all the prepared samples.