Reactivity, hydration kinetics, and microstructure evolution of activated copper mine tailings as supplementary cementitious materials

Document Type

Article

Publication Date

10-31-2026

Department

Department of Civil, Environmental, and Geospatial Engineering; Department of Materials Science and Engineering

Abstract

Copper mine tailings contain abundant aluminosilicate phases but generally exhibit limited cementitious reactivity because of their predominant crystalline mineralogy. This study investigated alkali-fusion activation of copper tailings using NaOH and Na₂CO₃ fluxing agents at 800 °C to enhance their potential as supplementary cementitious materials (SCMs). The results showed that alkali fusion effectively disrupted crystalline phases such as albite and hematite and promoted the formation of reactive phases, thereby significantly increasing pozzolanic reactivity. Compared with raw and thermally treated tailings, alkali-activated tailings exhibited greater calcium hydroxide consumption, higher heat release, and increased bound water, as confirmed by XRD, Frattini analysis, R3 calorimetry, SEM, and bound-water measurements. NaOH-assisted activation was more effective than Na₂CO₃-assisted activation because it induced stronger depolymerization, whereas Na₂CO₃ showed a greater tendency toward recrystallization. Although increasing alkali dosage enhanced activation, ' 50% dosage addition may promote nepheline formation and reduced reactivity. When incorporated into cementitious systems, the activated tailings accelerated hydration, promoted the formation of additional hydration products, particularly C-(A)-S-H gel and carbonate/aluminate-containing phases, refined pore structure, and contributed to matrix densification. Mortars incorporating 10–20% activated tailings as a cement replacement exhibited approximately 5–15% higher 28-day compressive strength, confirming that properly activated copper mine tailings can function as effective supplementary cementitious materials. Overall, alkali-fusion treatment with 20–50% activator dosage may provide a practical pathway for converting low-reactivity copper tailings into value-added cementitious materials.

Publication Title

Construction and Building Materials

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