Rheological and Morphological Analysis of Polymer Modified Bitumen

Rheological properties of the bitumen can be
easily assessed by empirical test but with the increase in
traffic volume and in axle loads, leads to the modification
of bitumen by the use of polymer, which enhances its
performance characteristics but significantly alters its
rheological properties. Although both conventional and
empirical binder tests are present to evaluate the
properties of binders but still there is a need to study the
binder properties in context with its flow characteristics
and its colloidal structure. This paper discusses some of
the results obtained from the laboratory investigation of
thermoplastics, linear low density polyethylene (LLDPE),
high density polyethylene (HDPE) and its interaction with
80 pen base bitumen. The rheological study was made
through penetration, ring & ball softening point and
viscosity. The observations were then related to the
changes in the rheological and morphological
characteristics of the modified bitumen. Field emission
scanning electron microscopy (FESEM) was used for the
morphological analysis of both virgin base bitumen and
PMB. The result shows that degree of modification
depends upon the solvating power of bitumen, oxidation
during mixing at higher temperature and interaction of
polymer with base bitumen. Compatible network can only
be formed when polymer is completely digested by the
base bitumen. The solvency power of polymer in base
bitumen also depends on polymer concentration and
presence of asphaltene and maltenes in the bitumen. The
results of the penetration, softening point and viscosity
reflect amazing behaviour of thermoplastic which may
exhibit promising performance, in rutting, fatigue and
water susceptibility when analyzed at later stage of this
study. In short best results were observed when the
concentration of the polymer was kept below 3%.