The diminishing quantity of natural resources has resulted in a search for alternative materials. Reusing industrial by-products, such as steel slag, provides opportunities for sustainable highway
construction practices due to the valuable space they occupy and the potential environmental impacts when they are stockpiled. In this paper, the mechanical suitability of steel slag as an unbound highway aggregate is investigated, and its performance is compared with that of traditional graded aggregate base (GAB) materials. In order to compare the behavior, three steel slag samples with different aging properties and five aggregate samples from different quarries were employed. The results indicate that resilient moduli and permanent. Deformation
characteristics of steel slag are comparable with those of traditional aggregates and can replace when used as a base or subbase course.