Improving the mechanical properties and performance of asphalt mixtures using high density polyethylene and crumb rubber powder

Asphalt cement is considered a necessary bonding material for asphalt mixture manufacturing; nowadays, in Egypt, there is a lack of the amount of asphalt cement due to the rapid progress in highways construction which is necessary for development. The main objective of this research is to use waxy asphalt as a compensatory material to address the shortage of asphalt in Egypt. After modifying its properties by adding polymer (HDPE) and crumb rubber powder (CRP) together because of waxy asphalt may have a harmful effect on road construction, and to obtain the best method of adding polymer and CRP to the asphalt mixture. The experimental program consists of six stages. In the first stage, a control mix M0 was designed without additives, followed by the second stage, in which six asphalt mixtures from M1 to M6 were designed, with varying ratios of HDPE and CRP, both applied through a wet process. The third stage also consists of six asphalt mixtures from M7 to M12, incorporating different ratios of HDPE in a wet process and CRP in a dry process. The fourth stage, included six asphalt mixes from M13 to M18, employing various ratios of CRP in a wet process and HDPE in a dry process. All mixes were designed using Marshall Test. From the prescribed three stages, the optimum asphalt mixtures were identified as M6, M8, and M17, respectively. In the fifth stage, the moisture sensitivity was measured as well as rutting characteristics for the control mix and the three optimum mixes. In the last stage, a Scanning Electron Microscope analysis was conducted. In conclusion, the results indicate that the waxy asphalt can be used by adding HDPE (Wet Process) and CRP (Dry Process) which significantly enhance the Marshall properties, as well as improving resistance to moisture damage and permanent deformation.