Experimental analysis of hydraulically bound mixtures made with waste foundry sand and steel slag

This paper presents the results of a laboratory study aimed at verifying the suitability of two types of industrial waste, foundry sand and steel slag, to be recycled in the aggregate skeleton of hydraulically bound mixtures for road foundations. The investigation involved a preliminary study of the leaching, physical and mechanical properties of the by-products and then the formulation of the hydraulic mixtures, in terms of Proctor, compressive and indirect tensile strength (ITS) tests, at various curing periods. In order to obtain a better mechanical characterization, the elastic modulus of the mixtures has been evaluated through static and dynamic tests, at different curing times. The results were completely satisfactory for all the mixtures designed, especially for that characterized by 80 % of steel slag and 20 % of foundry sand; it showed a compressive and ITS, at 7 days, up to 5.6 and 0.72 MPa respectively, depending on the mix and the cement content. Since the requisites for acceptance in the Italian Specifications and Standards have been satisfied and given the positive mechanical performance, it has been verified the possibility to use industrial by-products as integral substitutes of the natural aggregate in the production of cement bound granular materials for road foundations.