Exploring natural siderite (FeCO3) as a novel supplementary cementitious material

This study investigates siderite (FeCO₃) as a novel supplementary cementitious material (SCM) in ordinary Portland cement (OPC) systems. Freshly ground siderite significantly retards early hydration of C₃S and C₃A, primarily due to the formation of iron hydroxide that temporarily inhibits hydration. However, this effect diminishes over time, with hydration degrees and strength development at later stages (≥90 days) matching or exceeding those of systems with inert fillers. Siderite undergoes a “ferrolanic” reaction, consuming portlandite and forming hydrated Fe-bearing phases, influenced by redox conditions. Additionally, siderite improves concrete durability, reducing calcium leaching and potentially enhancing sulfate resistance through stabilized ettringite and Fe/Al solid solution phases. This research is the first comprehensive exploration of siderite as an SCM, highlighting its potential to address SCM shortages and contribute to CO₂ reduction in cement production. Further research is needed to evaluate long-term durability and practical applications in cementitious systems.