Temperature Zoning of Libya Desert for Asphalt Mix Design

Abstract

The current asphalt binder specifications in Libya are based on the Penetration Grade: penetration test is performed at 25°C. 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 Libya was carried out by using temperature data obtained from 8 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 Libya , the SHRP models at 50% level of reliability is recommended. The PG of roads that located in Libyan desert are classified to three zones (PG70-10, PG76-10 and PG82-10.PG 76-10 binder seems to be the most common grade that encompasses more than 70% area of Libya desert .However, currently none of the two local refineries produce the bitumen under penetration grade 60-70,that grade equivalent to PG 82-10 binder, thus it should be a concern for highway or the project location. The polymer modified asphalt binder are not produced by Libya refineries.