Optimizing Copper Slag as a Sustainable Precursor for Iron Phosphate Cement: Hydration Mechanism, Phase Transformation, and Environmental Safety

Author

• Wei Wang
• Hongyan Ma, Missouri University of Science and TechnologyFollow
• Xiunan Cai
• Dan Luo
• Zhicheng Xu
• Zhongqiu Luo
• Xintao Zhou

Abstract

Iron-rich copper slag (CS) has significant potential as a precursor for the synthesis of sustainable acid-base cement (AB). However, the roles and transformation behaviors of the diverse iron phases in CS during hydration remain unclear. In this study, the preparation conditions, early hydration behavior, transformation processes of iron components, and environmental safety of CS-based iron phosphate cement (CS-IPC) were systematically investigated. Under optimized conditions, with a CS/ADP mass ratio of 3.0 and a grinding time of 1.5 h, CS-IPC exhibited an initial setting time of 27.6 min and a flowability of approximately 159 mm. After curing for 3 and 28 d, the compressive strengths reached 25.3 MPa and 34.8 MPa, respectively. Hydration products were mainly composed of trivalent iron phosphates (Fe₃H₁₅(PO₄)_8·4 H₂O, FeH₂P₃O_10·nH₂O, FePO₄), iron hydroxide, and silica gel. Saturation index calculations indicated that, within the first 40 min of hydration, the iron phosphate phases were significantly oversaturated compared to iron hydroxide, suggesting their preferential formation. XPS and Mössbauer spectroscopy revealed that approximately 24.7% of the iron phases contributed to hydration products, with 10.7% from fayalite, 2.7% from magnetite, and 11.3% from an amorphous phase. Moreover, leaching tests confirmed that heavy metal release was well below the limits specified by GB-5085.3–2007 and TCLP-1311, demonstrating excellent environmental safety. This study highlights the active role of iron phases in acid-base cement systems and provides insights into the sustainable utilization of iron-rich copper slag in green construction materials.

Recommended Citation

W. Wang et al., "Optimizing Copper Slag as a Sustainable Precursor for Iron Phosphate Cement: Hydration Mechanism, Phase Transformation, and Environmental Safety," Construction and Building Materials, vol. 522, article no. 146211, Elsevier, May 2026.

The definitive version is available at https://doi.org/10.1016/j.conbuildmat.2026.146211

Department(s)

Civil, Architectural and Environmental Engineering

Publication Status

Full Text Access

Comments

Ten Thousand Talent Plans for Young Top-notch Talents of Yunnan Province, Grant YNWR-QNBJ-2020–063

Keywords and Phrases

Hydration product; Iron phase transformation; Iron phosphate cement; Iron-rich copper slag; Toxicity leaching

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

09 May 2026