بر خواص فيزيكي قير و دوام مخلوطهاي آسفالتي SBS اثر افزودن

The Effect of Adding SBS on Physical Properties of Bitumen and Durability of Asphalt Mixtures

Durability is one of the hot mix asphalt properties, that is actually the ability of mixture in maintaining itʹs quality against deleterious effects of both adverse weather and axle load during the time. The kind of aggregates and itʹs quality in addition to the type of bitumen and itʹs rheological properties and further more, the volumetric properties of mixture, have directly influence the durability and service life of pavement. In this investigation SBS block copolymer is tried as a modifier to improve defects of bitumen such as high thermal susceptibility (viscous behavior at high and glassy behavior at low service temperatures) and lack of cohesion after a short time, in this way, the durability of mixture will be improved. SBS copolymer has both elastomeric and plastomeric properties and blending with the bitumen causes changes in chemical structure of bitumen, so, physical properties such as softening point, penetration, viscosity and flash point become better. In order to assess the effect of SBS content on the degree of modification, conventional tests performed on base bitumen (60 -70 pen) and PMB containing 3, 5, 7, 9 percent of SBS by weight of total blend, then, the mixture including base bitumen and PMB with 5% SBS designed by Marshall method and complementary tests performed in optimum percent of bitumen resulting from designation. Stability, flow, tensile strength and modulus of resilient have significantly been increased and also the results of Marshall-immersion and moisture susceptibility tests show enhanced durability against water and freezing thaw cycle. Application of PMB by SBS seems to be desirable in regions with too heavy traffic load or too high daily or seasonally temperature difference.