Improvement in properties of bitumen using selected additives

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The properties of bituminous binders should meet specific requirements resulting from the load in the road pavement construction. The bituminous binder is expected to have the properties to ensure the durability of the asphalt mixture, the resistance of the asphalt mixture to permanent deformations at high temperatures (elastoplastic behaviour, stiffness) and at low temperatures to sufficiently stiffness and relaxation properties to resist low temperature cracking (cohesion and tensile strength of the binder). In order to improve the qualitative properties of bitumen and/or asphalt mixtures, additives and modifiers are applied e.g. to increase elasticity, improve adhesion to aggregate, reduce viscosity, increase ageing process resistance, prevent binder drainage from the surface of aggregate, etc. In some cases, the required properties can be modified by adding “natural” bitumen. Additives to improve adhesion are surfactants that reduce surface tension at the bitumen/aggregate phase and thus improve wetting. The results of the tested additives show their positive effect on the adhesion of bitumen to the aggregate determined according EN 12697-11 after 6 and 24 hours rolling in particular on the adhesion of paving grade bitumen to acidic and neutral aggregates (granodiorite, andesite, melaphyre). However, the results show that these additives also affect basic properties of bitumen binder as penetration, softening point, viscosity. The most significant changes have been made with the use of the Licomont BS100 and Sasobit wax additives (increase in the softening point of 13 to 43 oC) which move the bitumen to the values typical for the modified bitumen. By adding CWM and Wetfix BE additives, the bitumen became softer. In most cases, the additive has reduced the bitumen viscosity, the bitumen was less viscous, that allow better workability of the mixture and the possibility of lowering the working temperatures.