Steel slag is a by-product during the steel manufacturing process. It is a non-metallic ceramic material formed from the reaction of flux , such as calcium oxide with the inorganic non-metallic components present in the steel scrap. The reuse of steel slag reduces the need of natural rock as constructional material, hence preserving our natural rock resources and reducing the need for dumping ground. The steel slag will be done to ensure the aggregate is suitable for use as construction material. in 1993, steel slag aggregates have been used commercially in the region for road surfacing.

Steel slag contains significantly higher calcium oxide and iron oxide compared to granite rock. The good resistance to stripping by the steel slag aggregates indicates that the material is more superior to natural granite as road surfacing material. The superior adhesion of the steel slag with bitumen would also minimize potential moisture damage of the steel slag mix. The formulation of the road mixes using steel slag as aggregates has shown to give better rut resistance and mechanical stability, which indicates a more lasting wearing course for the road.

Researches regarding recycling and utilization of steel slag in different fields have been carried out in recent years. It was used as mineral additive for cement-based materials to improve mechanical properties of concrete. Some studies used steel slag to produce Portland cement with iron slag and limestone, and confirmed that the compressive strength of concrete was above standard values. Other researchers studied the characteristics of bricks made from steel slag and revealed that it reduced the required firing temperature. Steel slag could also be used to remove some hazardous substances such as ionic copper and ionic lead from waste water. In many researches, steel slag was used as aggregate in concrete. Researches have confirmed that the durability of concrete with steel slag was improved, and the compressive strength and split tensile strength were much higher than that with limestone. However, few reports were found about utilization of steel slag as aggregate in asphalt mixture.