ORIGINAL ARTICLE Experimental analysis of hydraulically bound mixtures made with waste foundry sand and steel slag Marco Pasetto • Nicola Baldo Received: 17 November 2013 / Accepted: 14 May 2014 Ó RILEM 2014 Abstract This paper presents the results of a labo- ratory 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 hydrauli- cally 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, depend- ing 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. Keywords Steel slag  Foundry sand  Hydraulically bound mixtures  Road foundations 1 Introduction In recent years the problem of recycling and disposal of wastes has become increasingly urgent for both economic and environmental reasons. Aggregate waste accounts for some 30 % in weight of the wastes produced in Italy [25]: this justifies the need for its recovery and exploitation to remedy a situation of environmental degradation caused by the creation of tips, possible unauthorised dumping, and to meet the growing demand for aggregates from a constantly declining number of quarries. Reserves of natural quarried materials are also diminishing, partly due to urban legislation that increasingly favours environ- mental conservation. Nevertheless, the reuse of waste materials has not yet met with wide consensus because of doubts about their technical-performance charac- teristics and, more importantly, as to whether they can guarantee the requirements of environmental compat- ibility when reused. M. Pasetto (&) Department of Civil, Environmental and Architectural Engineering, University of Padua, Via Marzolo 9, 35131 Padua, Italy e-mail: marco.pasetto@unipd.it N. Baldo Chemistry, Physics and Environment Department, University of Udine, Via del Cotonificio 114, 33100 Udine, Italy Materials and Structures DOI 10.1617/s11527-014-0333-4