Evaluating the Effect of Binder Constituents on Ferrous Carbonate Formation in Ferrock‐Type Cementitious Binder

Several industrial by‐products, process residues, and naturally extracted resources are rich in iron, providing a strong basis to explore their potential as cementitious materials. Cementitious composites in which ferrous carbonate is the primary binding phase have been investigated intermittently over the last decade. The Ferrock binder system, which uses iron‐rich materials, silica sources, and oxalic acid followed by CO 2 curing, offers an interesting alternative binder approach with the potential for lower CO 2 emissions. The main binding phase in this system is proposed to be ferrous carbonate (siderite); however, the mechanisms promoting the formation of this phase are not yet well understood. In this study, we investigate the effect of different components present in the Ferrock binder system on ferrous carbonate formation by using four different silica sources, varying oxalic acid concentrations, and different carbonate sources. Crystalline silica sources used as fillers tended to facilitate siderite formation; poorly crystalline goethite‐like phases were more pronounced with silica sources having high specific surface area. Increasing the concentration of oxalic acid did not appear to positively influence siderite formation, as enhanced chelation and surface passivation may reduce the availability of free Fe 2+ ions. Overall, the findings suggest that the Ferrock binder system could potentially be simplified by reducing the number of components while maintaining or enhancing the key mechanisms that promote siderite precipitation.