Steelmaking slag based on FMP S.r.l. patent: potential application in concrete production

Steel slag is an industrial by-product of steel manufacturing and can be categorized into BOF (basic oxygen furnace) slag, EAF (electric arc furnace) slag, and LF (ladle furnace) slag. Steel slag is useful in many fields such as agricultural fertilizer, soil improvement, road construction, and asphalt concrete. A massive utilization of the slag in concrete production is limited by its high porosity, water adsorption and possible phenomena of artefact expansion due to the presence of free lime (CaO) and periclase (MgO). In order to limit the risk of expansion, the steel slag is generally subjected to weathering in outdoor conditions during several months. These phenomena actually limit the use of slag in concrete at a maximum percentage of 25% w/w and this percentage requires a great increase of the chemical additives dosage (fluidifying agent). This study focuses on the use of EAF slag for the production of concrete with a degree of substitution of natural inert up to 80% by weight without the use of chemical additives after treatment of inertization/stabilization of the slag according to a procedure patented by Fmp innovative start-up. After the chemical and mineralogical characterizations of the slag, the operating parameter for inertization/stabilization of the artificial aggregate were optimized. Comparison tests were carried to determine the physico-chemical properties differences between the slag submitted to the treatment process and the untreated one. A concrete with substitution of 50% and 70% w/w of natural aggregate were designed in order to highlight the influence of slag aggregate on the concrete behaviour. Apparent density, porosity, permeability, compressive strength, tensile strength, and elasticity modulus were measured to assess the influence on concrete mechanical properties with different substitution of natural aggregate. Durability of the concrete samples was evaluated by accelerate aging tests.