Abstract

This study investigates the potential of indirect carbonation for CO2 sequestration and high-purity CaCO3 production using fluidized bed combustion (FBC) fly ash (FFA) and bottom ash (FBA). XRF and XRD analyses revealed high reactive CaO contents derived from lime, portlandite, and anhydrite. Calcium extraction using 1- mol NH4Cl achieved markedly higher efficiency than deionized (DI) water, yielding up to 17,586 mg/L of Ca²⁺ and producing 10.2 wt.% and 8.4 wt.% CaCO3 from FFA and FBA, respectively, with CO2 capture capacities of 45.0 and 36.8 kg per ton of ash. The precipitated CaCO3 exhibited high purity (56.1 %–57.2 %) and consisted mainly of calcite, with minor vaterite under lower pH. After carbonation, XRD confirmed complete removal of reactive CaO, while the amorphous content of the residues increased to 78.1 %–88.8 %, enhancing their suitability as supplementary cementitious materials (SCMs). Cement pastes incorporating 20 % FFA residue after indirect carbonation maintained adequate workability and achieved comparable early strength through sulphate-induced ettringite formation and partial consumption of Ca(OH)2 via pozzolanic reaction. These findings highlight indirect carbonation as a dual-benefit approach enabling CO2 sequestration and sustainable valorization of industrial by-products for low-carbon construction materials.

Department(s)

Civil, Architectural and Environmental Engineering

Publication Status

Full Text Access

Keywords and Phrases

CO2 sequestration; Fluidized bed combustion (FBC) ash; Indirect carbonation; Residue recycling; Supplementary cementitious materials (SCM)

International Standard Serial Number (ISSN)

0950-0618

Document Type

Article - Journal

Document Version

Citation

File Type

text

Language(s)

English

Rights

© 2026 Elsevier, All rights reserved.

Publication Date

04 Apr 2026

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