ATNAFU A. MENGISTU, DR. ALEMGENA A. ARAYA, DR. HABTAMU M. ZELELEW
The use of modifiers to enhance the rheological properties of asphalt binders and to improve the performance of flexible pavements has been long in practice, especially in the developed countries. The use of performance-based binder tests and specification systems in flexible pavement designs, such as the Superpave Method, has also replaced the traditional methods, such as Marshall Design, in most of the developed world. In most African countries, however, performance-based tests are still not practiced in the binder grading system. In addition, there is no significant effort to minimize pavement distress by using modified binder of improved visco-elastic property. Therefore, the objective of this study was to evaluate the rheological property of an 80/100 penetration grade bitumen partially replaced with different percentages of Reacted and Activated Rubber (RAR). RAR commonly contains 62% Crumb Rubber, 22% soft bitumen, and 16% Activated Mineral Binder Stabilizer (AMBS). Using this modifier laboratory produced samples of 15, 20 and 25 percent RAR by mass of total binder were prepared. Some Dynamic Shear Rheometer (DSR) tests, namely, Amplitude Sweep Test (AST), Frequency Sweep Test (FST) and Performance Grades (PG) determination were carried out. According to the master curves developed from the Frequency Sweep Tests, it is observed that the modifier helps to improve the complex shear modulus (especially the elastic modulus) at high temperature and low frequency, i.e., at the worest loading condition of pavements. The performance grade determination also depicted the increase in PG as content of modifier increases. Generally the study showed that it ispossible to improve the rheological characteristics of bitumen by partially replacing with RAR.