Eco-efficient valorization of gold tailings: A low-carbon binder with high early strength and reduced carbon footprint

Abstract

To address the demand for low-carbon binders with high early-age strength for gold tailings cementation, a sulfur-aluminum-ferric gold tailings cementitious material (SGCM) was developed using low-carbon sulfur-aluminum-ferric cementitious material (LSCM), gypsum, lime, and ordinary Portland cement (OPC). The binder composition was optimized through ternary and quaternary system experiments, and the corresponding hydration mechanism was investigated by isothermal calorimetry, X-ray diffraction, thermogravimetric analysis and scanning electron microscopy. The optimal proportion was identified as an LSCM:(gypsum + lime):OPC mass ratio of 1:1.2:0.4. At a cement-to-sand ratio of 1:4 and a filling concentration of 71%, the optimized SGCM achieved compressive strengths of 3.40 MPa at 3 d and 8.26 MPa at 28 d, showing superior early-age strength and competitive long-term strength compared with representative cementitious systems reported in previous studies. In addition, when applied at a reduced cement-to-sand ratio of 1:6, SGCM maintained compressive strength comparable to that of the OPC system at 1:4, while reducing the carbon emission factor by 70.2%; under the self-produced LSCM scenario, the material cost was further reduced by 15.0%. Mechanistic analyses revealed that increasing gypsum and lime contents promoted AFt formation but also transformed AFt into shorter and thicker crystals, whereas OPC incorporation enhanced early hydration, increased C-S-H generation, and densified the microstructure. AFt provided skeletal support, while C-S-H provided filling and bonding, and their synergy governed the strength development of SGCM.

Keywords

Gold tailings / Cemented paste backfill / Low-carbon binder / Early-age strength / Hydration mechanism

CRediT authorship contribution statement

Yukang Wu: Writing – review & editing, Writing – original draft, Data curation. Yuzhong Li: Supervision, Formal analysis, Conceptualization. Mengxia Xu: Investigation. Jingwei Li: Investigation. Qun Chen: Investigation. Maofeng Nie: Investigation. Hongkun Pai: Investigation. Hailong Liu: Investigation.

Data availability statement

The data that support the findings of this study are available from the corresponding author upon reasonable request.

Declaration of competing interest

The authors declare the following financial interests/personal relationships which may be considered as competing interests: Hongkun Pai and Hailong Liu are employed by Shandong Gold Group Xinyuan Mining Co., Ltd. The company provided the gold tailings used as experimental raw materials in this study. Apart from this material support, the company had no role in the study design, data analysis, interpretation of results, decision to publish, or preparation of the manuscript. 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

The authors gratefully acknowledge the support from the National Natural Science Foundation of China (52576127), and Jinan Scientific Research Leader Workshop Project (20233064).

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