Comparing how PET Particles Affect Some Engineering Properties of Bituminous Mixtures Fabricated by Asphalt Rubber and Conventional Binder

A laboratory study was conducted to determine the differential impact of waste polyethylene terephthalate (PET) on asphaltic mixtures produced using neat asphalt cement and rubber-modified binder. To achieve this, specimens were fabricated using two types of binder: base binder and rubber-modified binder. For the rubber-modified binder, 6% of Crumb Rubber (CR) by weight of the neat bitumen was mixed with the base binder, using the wet process. After mixing aggregates and asphalt binder, various heated PET contents ranging from 0 to 10% in 2% increments were used through the dry process to prepare Marshall specimens. Two different sizes of PET particles were employed: fine-graded PET ranging from 0.297 mm to 0.595 mm and coarse-graded PET ranging from 1.18 mm to 2.36 mm. Marshall stability, indirect tensile strength (ITS), and dynamic creep tests were conducted. Results revealed that the type of binder, regardless of the size of PET particles, plays an important role in the influence of PET on Marshall properties. The ITS ratio of the specimens depends on the air void, however, the trend for each amount of air void is the same for both types of mixtures (rubberized asphalt and conventional binder) containing either fine- or coarse-graded PET particles. The higher the percentage of PET in the mixtures (containing both modified and non-modified binder), the less resistance they showed to permanent deformation. In general, the size of PET had the same effect, and finer PET particles had better results in all mixtures regardless of the type of binder. Mixtures prepared with rubber-modified binder demonstrated good compatibility between CR and PET and exhibited better performance, while mixtures with the conventional binder were more sensitive to the addition of PET.