PERFORMANCE MODIFICATION OF SAUDI-ASPHALT
BINDERS USING SABIC POLYMERS
Hamad I. Al-Abdul Wahhab, Ibrahim M. Asi, Isam
Abaker, and M. Ghouse Baig
The 6th Saudi Engineering Conference, KFUPM,
Dhahran, December 2002 Vol. 2.
ABSTRACT
Asphalt
binder is a thermoplastic liquid, which behaves as an elastic solid at low
service temperatures or during rapid loading. At high temperature or slow
loading, it behaves as a viscous liquid. This classical dichotomy creates a
need to improve the performance of an asphalt binder to minimize the stress
cracking that occurs at low temperatures and the plastic deformation at high
temperatures. Use of polymer-modified asphalt binder is one of the solutions to
meet the required performance standards for the pavements of today. It appears
to be a logical, practical, and economical approach. In the Kingdom of Saudi Arabia,
most of the used asphalt-polymers are imported from abroad, which led to
increase the total construction cost. The main objective of this research is to
modify locally produced asphalt using polymer produced by Saudi Basic
Industries Company (SABIC). The study covered the asphalt binders produced by Riyadh refinery. Ten
polymers were identified as potential asphalt modifiers based on their physical
properties and chemical composition. Based on the preliminary laboratory
evaluation for the melting point of these polymers, five polymers were selected
for local asphalt modification. In the initial stage, required mixing time was
decided based on the relation between shear loss modulus and mixing time. The
optimum polymer content was selected based on Superpave
binder performance grade specifications. The suitability of improvement was
verified through the evaluation of permanent deformation and fatigue behavior
of laboratory prepared asphalt concrete mixes. The results indicate that the rheological properties of the modified binders were
improved significantly with sufficient polymer content (3%). They were also
influenced by the type and content of the polymer. The aging properties of the
modified binders were found to be dependent on the type of polymer. The fatigue
life and resistance to permanent deformation were significantly improved due to
the improvement in the rheological properties of the
binders. In general, the research has demonstrated the potentiality of
modifying local asphalts using SABIC polymers.
Keywords: Polymer, Rheology, Modified asphalt mixtures, Fatigue, Rutting,
Permanent deformation.