The Application of Modern Analytical Techniques to study Rheology and Morphology of Polymer Modified Bitumen

The influence of modification of 80 Pen bitumen using
polymer Polypropylene PP as modifier was investigated by
modern analytical tools like Fourier Transform Infrared
spectroscopy (FTIR), Gas Chromatography Mass Spectrometry
(GCMS), Carbon, Hydrogen, Nitrogen and Sulfur Analyzer
(CHNS), to understand the chemical changes in bitumen before
and after modification with its effect on the rheology and
morphology of the polymer modified bitumen PMB.
Morphological analysis was done using field emission microscopy
FESEM and atomic force microscopy (AFM). Rheology of the
polymer modified bitumen PMB is strongly affected by the
chemical composition, structure of the polymer, mixing time and
temperature. The results obtained from FTIR and GCMS
revealed that the alkenes (C=C), commonly known as olefins,
aliphatic unsaturated hydrocarbon and propene are the major
constituent of both virgin and modified bitumen. Oxidation of PP
PMB was also confirmed by the presence of carbonyl functional
group around 1739 cm1 and also by the elemental analysis of
CHNS analyzer, which is one cause of increase in the hardness of
PMB. The decrease in penetration value with the increase in
concentration of polymer in bitumen was not only by increase in
viscosity of modified bitumen but also by hardened phase
separated layer of partially miscible polymer acting as sheath
against penetration needle decreasing the value of penetration as
observed by AFM results. From AFM results it was revealed that
the increase in concentration of polymer in blend also increases
the thickness of phase separated polymer layer. The higher
percentage of asphaltene content in virgin bitumen, obtained by
n-heptane precipitation was confirmed by presence of honey bee
structured asphaltene by AFM scan result. Thus the analytical
tools are helpful in understanding rheological and morphological
changes brought by modification as the viscoelastic behavior of
polymer modified bitumen depend on concentration of polymer
used in the mix, mixing temperature, mixing time, mixing
technique, solvating power of base bitumen and molecular
structure of the polymer PP. Homogeneity of the blend is difficult
to achieve as higher molecular weight polymer was difficult to
disperse in lower molecular weight bitumen thus causing the
phase separation, that influences the chemical properties or in
short the rheology of the binder. It was revealed from these
characterization tests on modified binder that it would enhance
the mechanical properties of kept up to 3%.binder when the
concentration of the polymer in the blend.