Use of waste plastic blended bitumen for road construction and maintenance

Abstract

In this research work waste plastic (Low Density Polyethylene) is used as modifier to prepare samples required for tests to determine the engineering and rheological properties of the modified bitumen. Other objectives of the research were to analyze the effect of waste plastic modified bitumen on road quality and to assess the field performance of waste plastic blended bituminous pavement sections. To fulfil the objectives of the study, first of all waste plastic was collected in shredded form (<4.50mm) from old Dhaka. Then a total of 04 (Four) modified binders and mixes are prepared with 2.5%, 5%, 7.5% and 10% waste plastic content to perform the test of penetration, ductility, specific gravity, softening point, flash and fire point, loss on heating etc. At the same time one sample with virgin bitumen and one with 7.5% Pet bottle were also tested. For making this test sample, blending operation is done by mechanically and thermostatically controlled blender prepared by previous researcher (Hossain, 2006) is used. After performing the test of rheological/engineering properties Marshall Specimens were prepared with these binders and Marshall Tests were performed accordingly. The performances of modified bituminous mixes are evaluated by determining stability, flow, density and void in the mixes. In addition, to analyze the effect of waste plastic modified bitumen on road quality, a 100.0 m x 7.5 m road section is paved with this modified bitumen as well as adjoining same area with pure bitumen and performance is evaluated by some parameters like potholes, cracking, rutting, ravelling, edge breaking, and depression etc. for 1.5 years’ duration. The study results conclude that rheological properties like penetration, ductility and specific gravity of LDPE (waste plastic) modified bitumen decreases with increase of waste plastic contents while softening point, flash and fire point increases with increase in polymer contents in bitumen. The Marshal stability results reveals that the waste plastic (polymer) increases the stability values of the compacted mixes with increasing the waste plastic content in the bitumen up to optimum level (i.e. 7.5%). The flow values obtained in the Marshal test show slightly increasing pattern up to 7.5% waste plastic content, whereas the density of the compacted mixes slightly decreases with the increase of waste plastic contents in the bitumen. The effect of waste plastic on Air Void (Va), Void in Mineral Aggregate (VMA) and Void Filled Asphalt (VFA) is found insignificant. Data collected from the field demonstration show that less quantity of potholes, crack, ravelling and depression are formed on the road segment constructed with waste plastic modified bitumen than that of normal bitumen. Thus waste plastic bitumen enhances the longevity of the road. It is expected that using the output this research, the waste plastic materials can be used in bituminous roads works, resulting in minimization of the frequency of rehabilitation work and thereby providing an economic solution. It is also expected to substantially reduce volume of environmentally hazardous plastic and environmental pollution.