RELATIONSHIP BETWEEN RHEOLOGICAL AND CONVENTIONAL PROPERTIES OF BITUMEN

Abstract

Due to high cost of cement concrete roads, preference is usually given to construction of bituminous roads. These are constructed with bituminous material which binds mineral aggregate together. Although the proportion of bituminous binder surfacing is much less than that of aggregate, yet the quantity and quality of binder have a marked influence on behaviour of bituminous pavements. Bitumen is viscoelastic material, whose mechanical behavior depends on temperature and duration of loading. At low temperatures and short time loading, they behave as elastic solids; it shows high stiffness and brittleness. While at high temperatures and long time loading, they behave as simple viscous liquids i.e. exhibit high ductility and low modulus. At intermediate ranges of temperatures and loading time their behaviour is more complex. To accommodate the increasing traffic intensity and axle loads in varying climatic environments, high quality bitumen are required. Special binders are also needed for other applications, such as bridges, runways and slurry seals. Polymer modifiers increase the elastic responses and dynamic modulus of bitumen at intermediate and high temperatures, and influenced complex and stiffness modulus at low temperatures. It also reduced the temperature susceptibility All paving engineers and bitumen technologists feel that the present specification tests provide little to the engineer who is responsible for service performance of bitumen concrete pavement. Hence a full and complete rheological study of bitumen accurately judging its suitability would be helpful. In Dynamic shear iii rheometer, the temperature susceptibility of binders may be evaluated by measurements of various viscous and elastic parameters at different temperatures and frequencies. This gives the rheological parameters in terms of complex modulus and phase angle directly through the graph. The present study aimed at preparation of wide range of Crumb Rubber (CR) and Ethylene Vinyl Acetate (EVA) modified bitumen and to find the variations in conventional properties as well as rheological properties at different temperatures and loading conditions However, in some cases the consistency changes may increase with polymer content, but vary with bitumen grade and polymer type. For a given polymer content, the bitumen was observed to be less susceptible to EVA addition as compared to CR polymers. The results indicate that the complex modulus is 2 to 3 times more for bitumen modified with lower percentage of EVA (3%) as compared to lower percentage. of CR and this variation is increases by 6 to. 7 times for higher, percentage: of modifier(9%). Fatigue resistant of bitumen modified with lower percentage of EVA (3 %) is 2 to 3 times more than that of the bitumen modified with lower percentage of CR and this variation increases by 8 to 10 times for higher percentage (9%) of modifier.