Siderite-calcite (FeCO3–CaCO3) series cement formation by accelerated carbonation of CO2(g)–H2O–Fe–Ca(OH)2 systems

Carbonation-cementation and bulk reaction mechanisms are studied in systems containing closely packed mixes of particulate Fe (0) (~10 μm) and Ca(OH)2 (0%, 5%, 10% and 15% w/w of Ca(OH)2) subjected to elevated CO2-pressure (1, 5, 10, and 20 barg) and temperature (30 °C and 60 °C). Solid solutions of (CaxFe1-x)CO3 series minerals are observed through shifting and broadening of XRD-reflections with variations in Ca(OH)2 content, CO2-pressure and temperature. The product morphologies varied from rhombohedral in non-Ca(OH)2 systems, to distorted rhombohedral (at 60 °C) and scalenohedral (at 30 °C) in the systems containing Ca(OH)2. An X-ray diffraction-based interpolation method is developed to discern mixed and end-member carbonates for more accurate bulk phase quantification. Based on these observations, variations in cementation performances are explained. Exceptional formation of an Fe-LDH and a (Ca,Fe)-LDH has also been observed in some systems. Interestingly, these LDH phases were stable even after being exposed to ambient conditions for more than 75 days. [Display omitted] •CaxFe1-xCO3 (0 ≤ x ≤ 1) series cement formed by accelerated carbonation.•Fe substitution increases with carbonation temperature and CO2 pressure.•More carbonate ≠ more strength. Microstructure/morphology are important.•XRD Rietveld interpolation method to quantify proportion and bulk compositions.•Formation of Ca,Fe-carbonate-hydroxide hydrate (LDH) stable for at least 75 days.