Experimental evaluation of hydraulically bound mixtures for road foundations made with steel slags

This paper reports the results of a study conducted at the Experimental Road Laboratory of the University of Padova, to design cement bound granular mixtures for road foundations, characterized by a stone skeleton made exclusively with steel slags, of the Electric Arc Furnace (EAF) type, produced in Italian steel plants. The physical-geotechnical properties and the leaching behaviour of four different EAF steel slags have been evaluated, by means of the most relevant laboratory procedures used in the road technical sector. Hydraulic bound mixtures, characterized by the 100% content of EAF steel slags, have been studied in terms of Proctor, compression and indirect tensile tests. The results have clarified that the four steel slags investigated present selective applicability, dependant primarily on the appropriate grading size distribution. For one of them, the associated hydraulically bound mixtures have widely met the main Italian Contract Specifications (especially, in terms of compression and indirect tensile strength at 7 days, which were equal to 3.70 MPa and 0.40 MPa respectively), while for other two EAF steel slags, partially satisfactory results have been achieved, but still really promising and encouraging. The investigation has demonstrated that the recycle of the EAF steel slags, in total substitution of the natural aggregates for the road foundations mixes, is feasible, but has to be carefully evaluated and designed.