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. Doi: http://dx.doi.org/10.4038/jnsfsr.v40i4.5045 J.Natn.Sci.Foundation Sri Lanka 2012 40 (4): 311-320
Highlights
The durability and the long-term satisfactory performance of pavements are influenced and affected to a great extent by the pavement ingredients and their inherent properties
The asphalt binder grading system used in Sri Lanka is the penetration grading system
It is based on empirical tests and does not measure any fundamental engineering parameters of binders
Summary
The durability and the long-term satisfactory performance of pavements (road carriageways) are influenced and affected to a great extent by the pavement ingredients (materials) and their inherent properties. It is very pertinent to consider properties of the bituminous binders and the bitumen content as a quality control measure in a bituminous construction. The viscosity grading system was introduced in 1960. Both methods are empirical methods, based on past experiences and observations. Superpave grading system was developed as part of the Superpave research effort to introduce more accurate and fully characterized asphalt binders for use in hot mix asphalt (HMA) pavements. It was based on the idea that asphalt binder properties should be related to the conditions under which it is used. For asphalt binders, this involves expected climatic conditions and ageing considerations (Adedimila & Olutaiwo, 2003)
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