A comparative study on efficacy of waste plastic and waste Rubber in bitumen

Abstract

This study compares the use of recycled polyethylene terephthalate (PET) and crumb rubber (CR) when they are functionalized with waste vegetable oil and used as modifiers in bitumen. Granules of the same size were used for both modifiers, and both modifiers were treated with waste vegetable oil to enhance their compatibility with bitumen. The efficacy of the treatment was evaluated using Fourier transform infrared spectroscopy. Chemical analysis showed the appearance of intense peaks after bio-oil treatment for both oil-treated polyethylene terephthalate (PEToil-treated) granules and oil–treated crumb rubber (CRoil-treated) granules, indicating changes in the granules’ surface chemistry. Treated granules were introduced into bitumen to produce PEToil-treated bitumen and CRoil-treated bitumen. Then, the phase separation and the thermomechanical properties of the bitumen samples were studied. The results showed that PEToil-treated granules are more compatible with bitumen than are CRoil-treated granules, as evidenced by a lower separation index and a lower softening-point difference observed for PEToil-treated bitumen. PEToil-treated bitumen showed the higher viscosity and recovery; PEToil-treated bitumen increased the recovery by 47.36%, while no effect on the elasticity was seen when introducing the CRoil-treated into bitumen. The results also showed that bitumen containing PEToil-treated had better resistance to permanent deformation, while bitumen containing CRoil-treated showed better resistance to fatigue cracking. In addition, the moisture-induced shear-thinning index (MISTI) showed improvements in resistance to moisture damage when incorporating either PEToil-treated or CRoil-treated into bitumen, with PEToil-treated bitumen having greater resistance to moisture damage. Similarly, improved resistance against thermal-oxidative aging was observed for both PEToil-treated bitumen and CRoil-treated bitumen. Comparing the two bitumens after long-term aging, CRoil-treated bitumen had the lower increase in stiffness, and PEToil-treated bitumen had the lower decrease in phase angle. This in turn indicates that these two waste streams could complement each other, and that an optimized blend of PEToil-treated and CRoil-treated could lead to an enhanced performance while promoting resource conservation and recycling.