Cement based on HIsarna ^® slag – properties and performance evaluation

Abstract

The HIsarna ironmaking process is a promising, low CO ₂ alternative to the conventional blast furnace route, as it eliminates coking and ore agglomeration, improving energy efficiency and reducing emissions. However, its slag differs from conventional ground granulated blast furnace slag (GGBS), and its suitability for cement applications is still unclear. In pilot plant campaigns at Tata Steel (the Netherlands), multiple HIsarna slag batches with varying compositions were produced. This study evaluates one such slag (HIslag) as a supplementary cementitious material in blended cement. The liquid slag was water quenched, dried and ground, then used in a CEM III/A cement with 43 wt.‐% HIslag, 52 wt.‐% clinker and 5 wt.‐% gypsum. A reference CEM III/A with 43 wt.‐% GGBS and similar fineness was used for comparison. After detailed slag characterization, cement performance was assessed at mortar and concrete levels, including workability, compressive strength and durability (carbonation, chloride ingress, freeze–thaw resistance, sulphate solution expansion and seawater expansion). Results show that HIslag is a reactive and effective SCM, resulting in performance comparable to conventional slag cement, highlighting strong potential for decarbonizing both ironmaking and cement production.