Abstract:
Polymer modification of asphalt binders has increasingly become the norm in designing
optimally performing pavements. Pavements with polymer modification exhibits greater
resistance to permanent deformation and thermal cracking, and decreased fatigue damage
and temperature susceptibility. Polymer Modified binders (PMB) are effectively used in many
countries, such as USA, Europe, Australia and India over last three decades to construct
pavements with the superior performance and Extended service life.
In Sri Lanka 80/100 and 60/70 penetration grade bitumen has been used and it is observed that
both binders cannot perform satisfactorily due to their temperature susceptibility.
Modification of bitumen decreases the temperature susceptibility and therefore now it's time
to Sri Lanka to move forward from conventional binders to modified binders.
Initial step of this research was to study about functionality of polymer modified bitumen and
evaluating the need of polymer modified binders for Sri Lanka. After reviewing available data, it
was identified that most suitable polymer modifiers for Sri Lanka are SBS, EVA, SBR, PE and
Crumb rubber. Modification up to 4% - 8% of polymer is recommended and the modification
level can vary with the desired properties of binder. That depends on the factors such as
temperature, moisture level and other climatic conditions of the area and also traffic level.
PMB has to be characterized differently from penetration grade bitumen and the improved
performance properties are difficult to demonstrate with conventional empirical rheological
tests. This research is focused on reviewing the available PMB specifications and finally come
up with a set of required properties for modified binders relevant to Sri Lankan roads, required
testing methods and handling procedures for PMB. The final outcome of this research would
become a good initiating point for local highway engineers to move from conventional binders
to modified binders.
