Short term freeze-thaw effects on waste plastic bags and industrial polyethylene modified hot mix asphalt (hma)

Environmental and climate conditions are two very important factors that affect flexible asphalt pavements in roads. Asphalt Pavements (AP) are usually under continuous expansion and contraction effects from the nonstop increases and decreases of temperatures. As a result, AP structures are subjected to critical stresses and strains leading to cracks and defects. The physical and mechanical properties of hot mix asphalt (HMA) must be improved to resist the thermal cracking defects that generally occur in a pavement’s asphalt. Meanwhile, many types and huge quantities of waste plastics and industrial polyethylene are being generated. These wastes are harmful to the environment. This research aims to improve HMA specimen’s properties by adding waste plastic bags and industrial polyethylene to pure asphalt with replacement percentages of 2%, 3%, 4%, 5%, and 6% by total weight of asphalt. The optimal contents of additives to asphalt were found to be 4.6% and 4.1% for waste plastic bags and polyethylene, respectively. The effect of the short term freeze–thaw cycle on asphalt mixtures with and without additives was also studied. Durability curves and indexes were used to find the resistances of mixtures against freeze–thaw stresses. Three types of asphalt mixtures were prepared according to the Marshall method; all were exposed to freeze-thaw cycles according to the following timetable (1, 2, 3, 4, and 5) cycles, where each cycle represent 48 hours (24 hours freezing and 24 hours thawing). The first durability index (FDI) for asphalt mixtures with polyethylene had a lower loss rate in stability in one day, at 30.86 %, followed by asphalt mixtures with waste plastic bags where the value of FDI was 38.59%, while asphalt mixtures without additives gave an FDI value of 55.22%. Adding polyethylene and waste plastic clearly improves the mixtures properties and in turn increases the durability of asphalt pavements.