Re-use of steel slags in high performance asphalt concretes for road flexible pavements

The paper presents the results of a laboratory study, carried out at the University of Padua Road Research Laboratory, aimed at verifying the possibility to use a particular typology of Electric Arc Furnace (EAF) steel slag, in substitution of the natural aggregate, in the composition of high performance bituminous mixtures (Stone Mastic Asphalt, wearing course and base course asphalt concretes) for road flexible pavements, characterized by high steel slag content (above the 89% in weight). The experimental trial has been articulated in a preliminary study of the physical-geotechnical properties of the EAF steel slag and in the following mix design of the bituminous mixes, on the basis of the Marshall procedure. The performance of the asphalt concretes, in terms of stiffness and moisture susceptibility, have been investigated, through dynamic modulus tests at various frequencies and indirect tensile strength tests, for both dry and wet conditions. All the three different typologies of bituminous mixtures have completely satisfied the requisites for acceptance in the road sector technical standards (Marshall Stability and Quotient up to 1,530 MPa and 462 daN/mm respectively, depending on the mix) thus resulting as suitable for use in the construction of road infrastructures.