Recycling of waste foundry sand, steel slags and bottom ash in cement bound mixtures for road pavements

The paper discusses an experimental analysis, conducted at the University of Padova Road Research Laboratory, concerning cement bound mixtures for road foundations, with the aggregate matrix completely composed by industrial wastes, i.e. foundry sands, Electric Arc Furnace (EAF) steel slags and bottom ash from Municipal Solid Waste Incineration (MSWI), combined with different proportions. The laboratory analysis involved a preliminary study of the physical-geotechnical properties of the three different industrial wastes, then a mechanical characterization of the cement bound mixtures. The mix design has been conducted in terms of Proctor, compression and indirect tensile strength tests. At the end of the study, the dynamic elastic modulus of the mixtures was investigated through ultrasonic tests, also at different curing periods. The results have been completely satisfactory for all the mixtures designed, especially for that characterized by 30% of both foundry sand and bottom ash and 40% of steel slag, with a compression strength at 7 days up to 4.18 MPa and the corresponding indirect tensile strength up to 0.39 MPa. The experimental results have met the main Italian Contract Specifications, so demonstrating the feasibility to use industrial by-products as integral substitutes of the conventional natural aggregates in the production of cement bound granular materials for road foundations