Sustainable Utilization of Red Mud and Glass Waste in Alkali-Activated Cements: Design and Performance of Products

Abstract

Red mud (RM) is a hazardous waste that is generated in large quantities, and its sustainable, rational treatment and recovery is still a challenge. The aim of this research is to develop higher added value alkali-activated cements (AACs), which, by using red mud, can help to protect limited resources, reduce pollution, and produce alternative, "greener" building materials. During this work, industrial waste materials – blast furnace slag, red mud, and glass waste – were used to produce AACs suitable for traditional construction applications (e.g., load-bearing structures, foundation blocks, and walkways). Key parameters including the maximum RM content (recommended 21.7 wt% to maintain sufficient strength), composition of the activating solution, liquid/solid ratio, particle size, and reactivity of the glass waste were optimized. Glass waste reactivity was enhanced by high-energy grinding at 200 rpm for 90 minutes, resulting in a maximum compressive strength of 66.8 MPa, exceeding the highest strength class defined by relevant standards (EN 197-1). Mechanical properties were supported by microstructural analyses (SEM, FT-IR), and heavy metal behavior was assessed through leachate and adsorption tests. The AACs effectively immobilized heavy metals such as Cd, Ni, Pb, and Hg, with long-term leaching resistance and improved retention capacity compared to Portland cement-based mortars. Additionally, powder-based Pb2+ adsorption tests confirmed that RM-containing AACs offer enhanced performance in removing lead from aqueous solutions. Overall, these binders – containing up to 71.4 wt% combined industrial waste – demonstrate competitive mechanical and environmental properties, contributing to sustainable construction practices and potential wastewater treatment applications.