Steel slags are by-products from steel industries which can be used for the construction of roads and highways. Most of the physical and mechanical properties of steel slags are similar or better compared to conventional crushed stone aggregates. Most of the developed countries have successfully incorporating steel slags as an aggregate in hot mix asphalt, road base, sub-base and soil stabilisation in road works. This paper is a review of the physical, mechanical and chemical characteristics of steel slags and its utilisation in road pavement works. This paper highlights the flaws that need to be addressed, and further studies are required to develop an understanding of the potential of steel slag as a construction material. Hydrophobic property of steel slag provides a good adhesion with bitumen binder and helps to resist against the stripping and other defects of roads. Thus, it enhances a sustainable cost-effective green pavement in highway industry.

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This study has investigated the impact of graphene oxide (GO) in enhancing the performance properties of an asphalt binder. The control asphalt binder (60/70 PEN) was blended with GO in contents of 0%, 0.5%, 1%, 1.5%, 2%, and 2.5%. The permanent deformation behavior of the modified asphalt binders was evaluated based on the zero shear viscosity (ZSV) parameter through a steady shear test approach. Superpave fatigue test and the linear amplitude sweep (LAS) method were used to evaluate the fatigue behavior of the binders. A bending beam rheometer (BBR) test was conducted to evaluate the low-temperature cracking behavior. Furthermore, the storage stability of the binders was investigated using a separation test. The results of the ZSV test showed that GO considerably enhanced the steady shear viscosity and ZSV value, showing a significant contribution of the GO to the deformation resistance; moreover, GO modification changed the asphalt binder’s behavior from Newtonian to shear-thinning flow. A notable improvement in fatigue life was observed with the addition of GO to the binder based on the LAS test results and Superpave fatigue parameter. The BBR test results revealed that compared to the control asphalt, the GO-modified binders showed lower creep stiffness (S) and higher creep rate (m-value), indicating increased cracking resistance at low temperatures. Finally, the GO-modified asphalt binders exhibited good storage stability under high temperatures.

The two major distresses associated with flexible pavement are rutting deformation and fatigue cracking in world highways. This is mainly because of the increasing load and higher tire pressure of vehicles which are applied to highway pavements today. At the same time, the asphalt containing neat binders does not always performed as expected. As a consequence, these distresses reduce the design life of the pavement and increase the maintenance costs tremendously. Therefore, in order to minimize the distresses and increase the durability of asphalt pavement, there is need to improve the performance properties of neat asphalt binders. Many researchers reported that using different types of polymer to modify the asphalt binder could be a solution to minimize the distresses occurred in asphalt pavement and improve the overall performance of the pavement. Disposal of waste tires is a serious environmental concern in many countries. Several attempts were made in the past to modify asphalt binder using tire rubber powder to improve the performance of neat asphalt binders. It is believed that the use of Tire Rubber Powder (TRP) as an additive in the modification of asphalt binder can improve the binder performance properties, increase the durability of the pavement, and reduces the waste disposal problem. This study aims to review the previous studies conducted on the use of tire rubber powder in the modification of asphalt binder. It was observed that addition of tire rubber powder to the asphalt binder enhances the properties of modified binder. It was found that an increase in the percentage of tire rubber powder causes an increase in rutting factor (G*/sinδ) and decrease in fatigue factor (G*sinδ) indicating higher resistance against rutting and fatigue cracking. In addition, the use of tire rubber powder to modify asphalt binder is considered as a solution to enhance environmental and economic sustainability of pavements.