Bitumen is a black or dark brown non-crystalline solid or viscous material, composed principally of high molecular weight hydrocarbons, having adhesive properties, derived from petroleum either by natural or refinery processes and substantially soluble in carbon disulphide. Refer to Ali Akhber Yousefi (2002), bitumen in pure form is not suitable for modern roads and present traffic, therefore forced engineers to modify bitumen to improve its performance during service life.
The modified binder are more stable under heavy loads, braking and accelerating forces and shows increased resistance to permanent deformation in hot weather. It resists fatigue loads and having better adhesion between aggregates and binders.
TYPE OF BITUMEN MODIFIER AND ADDITIVE
There are 3 type of bitumen modifier, namely :
(1) physical modification
(2) chemical modification
(3) other type modification
Among many different polymers used in bitumen modification such as thermoplastics, thermosets, thermoplastic elastomers, the rubbers seems to be more attractive. Although thermoplastic elastomers such as styrene-butadiene-styrene triblock copolymer (SBS) or its hydrogenated forms and plastomers such as ethylene-vinylacetate copolymer (EVA) are good bitumen modifiers, rubbers are preferred due to their lower prices. In fact, bitumen is supposed to keep its physical and rheological properties constant at different service temperatures and loading conditions and transforms itself to a low viscosity Newtonian fluid at mixing temperature (165ºC). This type of bitumen is called “ideal bitumen”. Constant rheological properties in a wide range of temperatures correspond to rubbery behaviour. It is concluded that the rubbers should be able to modify bitumen properties very well.