Utilization of Syrian Natural Asphalt in Hot – Mix Concrete Mixtures

Abstract

This research covers evaluating the design and performance of hot-mix asphalt concrete mixtures for highways by utilizing Al-Beshery natural asphalt-sand material either alone or modified by compatible, lowcost and practical additives. Results of laboratory tests showed that Al-Beshery natural asphalt contains about 18% asphalt cement mixed with open-graded natural sand. Al-Beshery asphalt cement was found to be aged, stiff and hard as reflected by its high viscosity and low penetration values. Chemical analysis of this asphalt also indicated its hardness nature as explained by high asphaltenes content and heavy molecular weight of oils. Two types of rejuvenating agents were investigated to soften the aged Al- Beshery asphalt. The first is a compatible waste hydrocarbon material (lubricating used oil). The second is soft refinery asphalt (200-250 pen-grade). Different combinations between Al-Beshery natural asphalt and the two additive types were investigated to choose optimum contents of additives. Optimum contents for the waste hydrocarbon material and refinery 200-250 pen-grade asphalt cement were concluded as 6% and 30%, respectively, by weight of Al-Beshery extracted asphalt cement. Performance of designed asphalt concrete mixtures was measured under static and dynamic loading. Stability, indirect tensile strength, resilient modulus, fatigue cracking and rutting tests were all utilized to measure the different mechanical properties of the designed hot-mix asphalt concrete mixtures. Results of this research yielded promising improvements in the chemical and physical characteristics of Al-Beshery asphalt. Furthermore, performance of Al- Beshery treated asphalt concrete mixtures was significantly improved compared to the base case (i.e., no treatment).