Abstract:
There are three main asphalt binder classification
systems; penetration, viscosity and Superpave. The penetration
grade 60 –70 binder is used for road constructions in Sri
Lanka. The objective of this study was to review the existing
asphalt binder grading systems and find the most suitable
grading system for Sri Lanka. Performance of the road sections
constructed with different penetration grade binders were
examined and it revealed that the binder grade significantly
affects the performance.
A survey was conducted among the professionals
involved in the road construction industry to evaluate the
current practices. Laboratory test results of the University of
Moratuwa and test reports collected from road contractors and
the Research and Development (R&D) Division of the Road
Development Authority (RDA) were investigated. The test
results revealed that binders used in the industry are highly
temperature susceptible, though the binder has complied with
the standards.
Data collected from the Meteorological Department for the
last 20 year period were analyzed to estimate the maximum
and minimum pavement temperatures, which are required
for Superpave binder grading. An algorithm validated for
Sri Lankan conditions was used to estimate the pavement
temperature from ambient temperature. The requirement of
different binder grades for different zones has been identified
and a GIS map was developed to select the suitable binder
grades for specific road sections in Sri Lanka. PG 58-16 can
be recommended for majority of roads while PG 52-10 can be
recommended for the regions in the central hilly area of the
country where low temperature prevails. Similarly, AC 30 and
AC 20 can be specified for high and low temperature zones,
respectively.
Keywords: Asphalt, binder
