Determination of Temperature Zoning for the Great Lakes Region of Africa Based on Superpave System

"Majority of the countries in the Great Lakes region of Africa still rely on the traditional Penetration grading approach for characterizing asphalt binder, as opposed to the more recent and reliable approach of SuperPave (Superior Performing Asphalt Pavements). This paper outlines the steps and criteria of selecting Performance Grade (PG) of bitumen to be used in selected countries of the Great Lakes region, based on the SuperPave approach. In Superpave, high-temperature (HT) Performance Grade required for a given region of project is determined based on a rutting damage model. HT equation is a function of layer thickness, climatic conditions, and latitude of the site (Mohseni et al, 2005); whereas, Low-temperature (LT) Performance Grade is selected using an algorithm developed from LTPP climatic data, and that relates the minimum pavement temperature to minimum air temperature, latitude, and depth (Mohseni, 1998). Study of climatic conditions of selected countries (Uganda, Kenya and Tanzania) in the great lakes region shows that the maximum pavement design temperature is 64 ºC, while the minimum pavement design temperature is -10 ºC. Further, the temperature zoning is distributed into three geographical areas, namely PG 64-10, PG 58-10 and PG 52-10 according to the collected and studied data.

Novel Method for Assessing Moisture Damage in Asphalt Mixtures

Moisture damage is a major cause of early pavement deterioration and often accelerates other distresses such as rutting, fatigue cracking, and raveling. Water infiltrates into the pavement structure through the cracks and air voids and weakens the adhesive bond between the binder and the aggregates as well as the cohesive bond between the binder particles. Several tests have been adopted to test for moisture susceptibility, most commonly the Modified Lottman (AASHTO, T283) and the Hamburg Wheel Tracking Device (AASHTO, T32404), however, these tests correlate poorly with field results and do not properly replicate the conditions which a pavement structure experiences in the field. Also, the mechanism which determines the mode of failure due to moisture damage, being either adhesive or cohesive, remains largely not understood, and the research tackling this issue is very scarce. The objective of this study is to introduce a new testing procedure based on the pull-off approach and study the factors which influence the mode of failure of the samples, such as the asphalt film thickness and loading rate