Carbon-negative slag-based binders: A review of steel slags

The cement industry is a major contributor to global CO 2 emissions, highlighting the urgent need for environmentally sustainable alternatives. Steel slags, by-products of the steelmaking process, are commonly landfilled, resulting in environmentally unfriendly land use and pollution. Due to their inherent alkalinity and carbonation reactivity, these slags offer significant potential for CO 2 sequestration through carbonation. This has led to the development of carbonation-activated slag-based binders. This paper provides a comprehensive review of the development of slag-based binders, with an emphasis on compositional analysis, carbonation mechanisms, and key factors affecting performance. In addition, existing life cycle assessments under various application scenarios are discussed to evaluate the carbon footprint of slag-based binders. The review outlines the current challenges and proposes future research directions for the practical use of slag-based binders. • Steel slags offer strong potential for CO 2 sequestration via carbonation. • Carbonation forms a CaCO 3 –SiO 2 structure enabling slag-based binder performance. • Variable slag composition demands standardised production and testing methods. • Key challenges include limited carbonation depth, acid attack, and metal leaching. • Future work targets advanced carbonation, wider applications, and industry integration.