Review of asphalt binder grading systems for hot mix asphalt pavements in Sri Lanka

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 SriLankan 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.