Sodium oxalate activation of basic oxygen furnace slag for building materials
Winnie Franco Santos, Jan-Joost Botterweg, Stefan Chaves Figueiredo, Katrin Schollbach, Sieger van der Laan, H.J.H. Brouwers
Abstract
Basic oxygen furnace (BOF) slag is a waste from the steel-making process characterised by its low hydraulic behaviour and heavy metals content. This study investigates activation of BOF slag with disodium oxalate to enhance the early hydration kinetics, microstructure development and heavy metals retention to develop it as a 100% replacement alternative for ordinary Portland cement. The results reveal that the activator boosts the reactivity not only of brownmillerite and calcium silicate but also Mg-wuestite. The main products formed are hydrogarnets and calcium-silicate-hydrate (C-S-H) gel. The maximum dosage added of 3 wt.% reached sufficient strength of 32.8 MPa at 28 days, being the most promising mixture. Leaching results of heavy metals are below the Dutch Soil Quality Decree limits. In summary, the BOF slag-oxalate cement offers an attractive approach for the future of steel-making and the building materials industry.