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The current asphalt binder specifications in Pakistan are based on the Penetration Grade:
penetration test is performed at 25oC. Penetration is an empirical measure of the consistency that is used
as an empirical indicator of the rutting and fatigue susceptibility of asphalt binder, and is not related to
pavement performance. The new mix design methodology developed under the Strategic Highway
Research Program (SHRP), called the SUPERPAVE is a performance-based approach. The first step in
the implementation of SUPERPAVE methodology is to establish high and low pavement temperatures for
a location. The temperatures define the required Performance Grade (PG) of asphalt binder. This paper
documents the initial ground work towards implementation of SUPERPAVE mix design for establishing
high and low geographical temperature zones. The temperature zoning of Pakistan was carried out by
using temperature data obtained from 64 weather stations. The SHRP and LTPP prediction models were
utilized for predicting pavement temperatures. A significant difference was observed between the
predicted pavement temperatures from both the models. The SHRP model gives higher, high temperature
PG grade providing additional protection against rutting. Since rutting is the most common distress on
flexible pavements in Pakistan, the SHRP models at 98% level of reliability is recommended. PG 70-10
binder seems to be the most common grade that encompasses more than 70% area of Pakistan. However,
currently none of the two local refineries produce PG 70-10 binder, thus it should be a concern for the
highway agencies. The polymer modified asphalt binder produced by Attock refinery (A-PMB)
corresponds to harder PG 76-16 while A-60/70 (PG 58-22) or K-60/70 (PG 64-22) produced at Attock
and National refineries respectively are softer compared to the PG 70-10. Harder grade is more prone to
cracking, whereas softer grade of more prone to rutting. Consequently, the current construction
practices which utilize A-60/70 or K-60/70 may be prone to excessive rutting.
M. Waseem Mirza, Zahid Abbas, Mujasim Ali Rizvi. (2011) Temperature Zoning of Pakistan for Asphalt Mix Design, Pakistan Journal of Engineering and Applied Sciences, Volume 8, Issue 1.
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