Active Rheology Control in Cement Pastes: Selection of Potentially Magneto‐Responsive Residual Materials Based on Iron Content and Iron Oxide Phase

Abstract

Active rheology control (ARC) using magneto‐responsive particles enables on‐demand adjustment of the rheological properties of fresh cementitious materials. This study investigates the influence of iron oxide phase and total iron content on the suitability of magneto‐responsive materials for ARC applications. Two iron oxide pigments (Fe ₃ O ₄ and Fe ₂ O ₃ ) and two steel slags with the same magnetite content but differing total iron concentrations were characterized. Their chemical–mineralogical composition and magnetic properties were determined, while their magnetorheological behavior was evaluated using oscillatory rheometry under applied magnetic field. The results show that the type of iron oxide phase has a dominant influence on magnetorheological behavior, while total iron content alone is not sufficient to predict performance. The Fe ₃ O ₄ ‐based system exhibits a significantly stronger magnetorheological response under magnetic field than the Fe ₂ O ₃ . Among the residual materials, both slags increase the storage modulus of cement pastes under applied magnetic field. Overall, the findings highlight that the iron oxide phase is a key parameter governing ARC performance, providing guidance for the selection of sustainable magneto‐responsive materials for cement‐based systems.