Modification of bitumen with waste plastics for road construction

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2013-12-16
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The absence of efficient management of municipal solid waste (MSW), with regards to used plastic components, which have overwhelmed our major cities and towns, is a growing challenge for developing countries including Ghana. Another challenge is the deformation of our roads due to excessive traffic and binder quality used; thus, new technologies need to be adopted to improve road construction. This study examines the effect of blending waste thermoplastic polymers, namely high density polyethylene (HDPE) and polypropylene (PP) in conventional AC-20 graded bitumen, at different plastic compositions. The plastics were chopped and blended with the bitumen ‘in-situ’, with a shear mixer at a temperature range of 160 ºC-170 ºC. Basic rheological parameters such as penetration, ring and ball softening point and viscosity test were employed to determine the resulting changes from the base bitumen. FTIR spectroscopy was also employed to study the chemical functionalities present in the bitumen composite. Three prominent peaks were identified in the spectrum of the unmodified bitumen, occurring at the 3000-2850cm-1 IR frequency range, typical of aliphatic –C-H symmetrical and asymmetrical stretches in alkanes. CH2 and CH3 bends were also observed at the characteristic frequencies of 1465cm-1 and 1375cm-1 respectively. A low intensity peak was observed within the 2400 cm-1-2100cm-1 range, indicating the presence of a very weak -C≡C- or -C≡N group with an absorbance of precisely 0.12. The properties of the unmodified bitumen were found to be enhanced with the changes in the rheological properties of the polymer modified bitumen (PMB). The viscosity of unmodified bitumen was enhanced with the addition of the polymers and thixotropic effect was observed for both HDPE and PP at 60°C. For all modified binders prepared, the penetration values decrease as polymer ratio increases whilst, softening temperature generally increases as polymer ratio increases. The most compatible and incompatible blends for HDPE were respectively observed at 2% and 3% polymer loading. The most enhanced, homogenous blend is achieved with PP at 3% polymer loading. The use of waste commodity plastics in binder modification carries the advantage of a cheap and effective means of enhancing conventional binder performance and is an alternative way to utilise plastic waste.
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A thesis submitted to the Department Of Chemistry, Kwame Nkrumah University of Science and Technology, Kumasi in partial fulfilment of the requirements for the award of Master of Philosophy degree (Mphil) in Polymer Science and Technology, June-2013
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