Comparing The Effect of Using Waste PET Polymer on The Performance of Asphalt Concrete Made of Unmodified and Rubber Modified Asphalt Binder

In this research, in order to study the effect of using PET on the performance of asphalt concrete containing rubber modified and unmodified binder, PET particles were added into the mixtures in different dosages of 0, 2, 4, 6, 8 and 10% (by the weight of binder). After determination of the optimum binder content of the mixtures, the specimens were made and subjected to Marshall, indirect tensile and dynamic creep tests. The dynamic creep tests were performed using a universal testing machine (UTM-10) by applying a vertical stress of 300kPa at a temperature of 40°C, to investigate the resistance against permanent deformation. Results show that adding PET into the mixtures improves the Marshall stability and Marshall Quotient compared with those for the control mixture. However, the trend of variation with PET content is different for the unmodified and rubber modified mixtures. While the Marshall stability and Marshall quotient increase with increasing PET content in the rubber modified asphalt concrete, they reach to the highest value by adding 4% of PET into the unmodified mixture, and after that they decrease with increase of PET content. The indirect tensile test results show that the indirect tensile strength (ITS) of the mixtures made by rubber modified and unmodified binder and containing air voids content within 6.5 to 7.5%, reaches to its highest value by adding 2% of PET. However, for the mixtures containing air voids content within 3-5% ITS decreases with increasing PET content. Dynamic creep tests reveal that the resistance against permanent deformation decreases with increasing PET content in both mixtures, with a lower reduction in the mixtures made by rubber modified binder. Comparing the results of Marshall Quotient and dynamic creep tests show that the deformation behavior of PET modified mixtures is different under static and dynamic loading. While, the mixtures resistance against deformation under static loading is improved, under dynamic loading they show less resistance than the control mixtures. Also, results of this research show that PET is less effective on the rubber modified mixtures than the unmodified mixtures.