Properties of steel slag aggregate and steel slag asphalt concrete

Ferrous slags (blast furnace slag, steel slag, ferro-alloy, etc.) are the industrial byproducts from a greatest interest to the pavement construction industry, given their wide availability and scope of uses. Above that the production of aggregate from slag instead from rock would decrease the amount of raw material exploitation and enable further environmental benefit since less industrial byproducts would be disposed in landfills. It is estimated that approximately 14 million tons of blast furnace slag is produced annually in the United States, and only less than 10 percent of that amount is disposed of in landfills. Rest of the blast furnace slag has been used as an aggregate in Portland cement concrete, asphalt concrete, road base, railway ballast, or as mineral admixture in blended cement. Steel slag is somewhat less used (approximately 7, 0 to 7, 5 million tons per year in the US) as construction material because of their high bulk density and potentially expansive nature. Nevertheless, steel slag can be processed into a coarse or fine aggregate for use in dense- and open-graded hot mix asphalt and in cold mix or surface treatment applications. Steel slag aggregates have numerous favorable properties such as angular shape, rough surface texture, good abrasion resistance, good soundness characteristics, and high bearing strength. Until the Regulations for construction products in Croatia didn’t get in force in 2005, there was no technical regulation or specification for the evaluation of possible use of slag aggregates in constructions. Therefore there is no much experience in Croatia in the application of slag aggregate and the practical application is rather in the research phase. In this paper testing results of one type of steel slag aggregate produced in Croatia are presented, as well as results of the asphalt produced from 75 % of steel slag aggregate and 25 % of limestone rock aggregate. Analysis of results showed that asphalt produced with steel slag aggregate has good resistance to permanent deformation, high stability with good flow properties and high stiffness modulus.