Alkali-activated materials are regarded as a potential sustainable building material with industrial by-products fully replacing ordinary Portland cement. Five million tonnes of electric arc furnace slag are produced annually mostly to be recycled as low value aggregates in several construction applications. This study examined the possibility of valorising the understudied slag as a precursor in alkali-activated concrete. The material, supplied free and available in abundance as a waste, presents a significant potential to produce sustainable concrete. Hence, the mechanical and durability properties of electric arc furnace slag-based alkali-activated concrete were examined. After that, using a sustainability assessment framework called ECO2, the combined whole-life cycle assessment of the environmental and economic impact was calculated for several mixes that combined electric arc furnace slag and fly ash as precursors. The increasing amount of slag content led to a decline in mechanical performance, though there was an equivalent durability-related performance; mixes with electric arc furnace slag showed equivalent slump and resistance to carbonation, and enhanced resistance to chloride ion penetration. Furthermore, slag-based concrete exhibited significant improvement in the overall ECO2 sustainability score due to its minimal environmental and economic impact.