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.
