ABSTRACT
Aggregates are one of the key building materials used in the construction industry and the largest portion of an asphalt pavement. Aggregates are generally naturally derived from minerals and sometimes have been further mechanically processed to be better suited for specific applications. Synthetic aggregates are also used in asphalt pavements and are most commonly blast furnace slags from the steel industry. Crushed stone, gravel, and sand are the natural types of aggregate used in the construction of an asphalt pavement. ASTM defines aggregates as a granular material of mineral composition such as sand, gravel, shell, slag, or crushed stone, used with a cementing medium to form mortars or concrete, or alone as in base course, railroad ballast, etc. (ASTM 2001a).
