Abstract
Iran-produced bitumen under the circumstances of severe temperature fluctuation, heavy traffic load and raining/freezing conditions show low efficiency; therefore, it is necessary to improve its properties accordingly. Existence of weakness in produced bitumen result in failure occurrence in asphalt pavements during service life of asphalt roads. Given the existence of considerable reserves of Gilsonite in Iran, its low costs compared with other additives and its remarkable properties, we can study asphalts modified by Gilsonite. At the present time, little research has been conducted on this modifier in the world and Iran (which its properties are still not quite evident for researchers). The most important failure in flexible pavements is permanent deformations which are known as rutting. Rutting is longitudinal depression in the wheel path in bituminous pavements. The rate and depth of rutting depend on the internal factors such as bitumen properties, aggregate, mixture properties and thickness of pavement layers. In this lab study, with regard to the technical and executive issues, common functional performance-based tests of bitumen were performed on specimens through addingGilsonite with 0, 2, 4, 6, 8, 10wt.% of made bitumen specimens. Then, the optimum percentage was calculated using the AHP. The specimens containing pure bitumen 60–70 and modified bitumen 60–70 with Gilsonite in two different aggregations (4 and 5) were made and the effects of adding Gilsonite in Marshall Stability and flow, indirect tensile strength and moisture sensitivity, as well as dynamic creep, and resilient modulus were evaluated by the UTM device. The research showed that adding Gilsonite to bitumen in hot asphalt mixtures considerably increases Marshall Stability and resilient modulus parameter in asphalt specimens. However, resilient modulus test indicated a significant reduction in flexibility property of asphalt mixtures made of modified bitumens. Moreover, increasing the flow number obtained from the dynamic creep test indicate the increase of rutting resistance.
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