A Review of the Natural Bitumen and its Effects on the Properties of Bitumen and Asphalt Mixture

In this study after a review on researches, the properties of modified bitumen and asphalt mixtures with Gilsonite additives have been evaluated. Gilsonite is a hydro-carbonic substance derived from oil in the oil-rich regions and it is observed in abundance and this material due to low price and improving properties of asphalt mixture can reduce the cost of road construction projects. Research conducted shows that the increase of gilsonite to the asphalt mixture increases the fatigue strength and stiffness modulus of modified asphalt mixture. With the increase in modulus it can be understood that the pavement would show higher stiffness and longer fatigue life. The results indicate that the gilsonite increases the viscosity and decreases the degree of penetration, and with respect to its lower price compared to other additives such as polymer and industrial additives, could be a viable alternative to improve the rutting at high temperatures in asphalt pavements. The studies show that the additive enhances the strength and indirect tensile strength of mixture of pavement and with increasing the ratio TSR, resistance to moisture asphalt mixture is improved and stripping asphalt mixture is prevented and can be used as an anti-stripping agent for siliceous aggregates. Also, due to the ability to withstand high shear forces can cross at intersections, bus stops, especially in extremist bus routes, around the field and also used runway pavement.