Synergistic utilization of bauxite residue (red mud) and multiple solid wastes for low carbon precast concrete materials: Mechanical performance, mechanism and sustainability assessment

Abstract

This study investigates the performance and mechanism of bauxite residue (red mud) and multiple solid wastes as active cement replacements in precast concrete. The effects of mixing ratio, water-to-binder ratio, and steam-curing temperature on mechanical properties and microstructural evolution were systematically evaluated. Results showed that incorporating 10%–20% red mud significantly accelerates early hydration under 45–60◦C steam curing, enabling demoulding strength above 15 MPa within 8 h. Microstructural characterization reveals that the enhancement originates from the alkali–thermal synergistic mechanism: alkali released from red mud promote dissolution of fly ash glass phases and formation of C–(A)–S–H gels, which interweave with AFt to generate a dense microstructure. A suitable steam curing temperature will further enhance this synergistic effect. This synergistic hydration not only improves early mechanical performance but also supports stable long-term strength development. Sustainability assessment further indicated that the optimized mix design reduces carbon emissions by 46.1% and lowers material cost by 40.8% compared with the pure cement system. Overall, this study clarifies the alkali-thermal synergistic hydration mechanism in solid-waste-based precast concrete and demonstrates an effective pathway for large-scale synergistic utilization of industrial solid wastes such as red mud.

Keywords

Red mud / Precast concrete / Synergistic effect / Compressive strength / Carbon emission

CRediT authorship contribution statement

Shanliang Ma: Writing – original draft, Visualization, Resources, Methodology, Investigation, Formal analysis, Data curation, Conceptualization. Xiaoming Liu: Writing – review & editing, Validation, Supervision, Funding acquisition, Conceptualization. Zengqi Zhang: Writing – review & editing, Validation, Supervision, Funding acquisition, Conceptualization. Yang Shao: Writing – review & editing, Methodology, Investigation, Data curation. Yinming Sun: Writing – review & editing, Validation, Supervision. Siyi Li: Writing – review & editing, Investigation, Data curation. Weijie Du: Writing – review & editing, Investigation, Data curation. Lilei Zhu: Writing – review & editing, Resources, Investigation, Data curation. Junyong Wang: Writing – review & editing, Resources, Investigation, Data curation.

Declaration of competing interest

The authors declare the following financial interests/personal relationships which may be considered as competing interests: Lilei Zhu and Junyong Wang are currently employed by China MCC22 Group Corporation Ltd. Other authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgements

This research work was supported by the National Key R&D Program of China (2022YFB2602602) and the National Natural Science Foundation of China (No. U23A20557, 52478232).

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