Synthetic granulated blast furnace-like slag from bauxite residue smelting and its use in multi-component Portland composite cement

Abstract

This study investigates the composition and reactivity of two GBFS-like slags produced from bauxite residue (BR). The composition of the slags was analysed using a multi method approach. The hydraulic reactivity was assessed in Portland composite cement and with the addition of anhydrite, limestone and combinations thereof. The presented approach is further discussed in the context of the full valorisation of BR and the economic as well as environmental implications. Both slags demonstrated a good strength contribution at a 25% substitution rate. Both failed the minimum strength requirements for GBFS according to EN 15167–1, using a 50% substitution rate. Anhydrite and limestone additions improved the early strength development. In conclusion, this work demonstrated that it is possible to convert 100% BR to valuable products. However, the production of slags with a GBFS-like chemistry required the use of high quantities of slag-forming agents. Also, the process will be energy intensive and costly. Still, the approach can be economically viable, as several valuable products can be generated. The possible avoidance of landfilling or even to recovery landfill capacities presents another important economic benefit.