DIGEST 2006 - Sabita

educed to, for example, four, if a
single lower temperature is
adopted. These issues, along with
the temperature intervals of the
classification system, will be
debated by the RPF Binder
Working Group.
Temperature zones
It is indeed encouraging to note
that SA bitumen meets the
standards adopted in the USA,
especially the good low
temperature classification;
however, there is still some work
to be done, including identifying
appropriate temperature zones in
SA and appropriate binder tests,
especially the simulation of long
term ageing. For this purpose,
alternatives to the PAV such as the
Belgian Rotating Cylinder Ageing
Test (RCAT) and possibly a
prolonged RTFOT, are under
investigation.
In addition, the different
requirements of surface seals
versus asphalt surfacing, need to
be taken into account. The
selection of critical binder test
parameters and the identification
of appropriate limits to reliably
interpret susceptibility to, for
example, permanent deformation
or cracking, will also need be
investigated. Zero Shear Viscosity
has been recognised
internationally as a critical
property that could assist in
identifying permanent
deformation, and will need to be
considered.
Acknowledgements
The refineries are commended for
supporting this study, as well as
Prof. Bahia and his team for
carrying out the testing at such a
reasonable cost and for providing
technical insights. We now have a
snapshot of really useful
rheological information to guide us
with possible bitumen gradings. It
does not stop here, however;
research on applicable long-term
ageing simulation tests and
experimental (non-conventional)
tests on the binders, will continue
in the quest of a suitable system
for South Africa.
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