Recycling copper tailings to develop in-suit and low-carbon cement-based sensors for health monitoring of mining infrastructure

In this study, the effect of copper tailings (CT) as partial cement replacement on nanocarbon black (NCB)/cement-based sensors (NCBS) was systematically investigated. The results demonstrated significantly improved electrical conductivity and enhanced piezoresistive sensing performance with increasing CT content. The developed CT/NCB cement sensors (TNCBS) exhibited superior sensing performance under dynamic loading with various frequencies and amplitudes. The average gauge factor (GF) of optimized group reached 93, and the piezoresistive-based electric signal is highly stable, linear, repeatable, synchronous, and presented with minimal signal noise. Based on phase composition, mineralogical, and microstructural analyses, the novel mechanism is that the spontaneous in-situ growth of an NCB/C-A-S-H layered product on the surface of CT particles was facilitated by an enhanced pozzolanic reaction. Owing to the unique dual nature of CT, the active components, including amorphous phases and alkali-susceptive mineral phases, participate in the reactions, while inert portion serves as a base template for the formation of the NCB/C-A-S-H layer. CT particles with this layered structure act as ‘functional micro-aggregate’, promoting the formation of extensive NCB conductive networks and enhancing the conductive efficiency and sensing performance through a hierarchical conductivity-strengthening effect. These findings provide valuable insight into the benefits of incorporating mine tailings into cement-based sensors (CBS), offering innovative, sustainable, and affordable solutions for the health monitoring mining infrastructures. • DC resistivity and AC impedance of CT/NCB cement mortar is reduced with increasing CT. • Piezoresistive sensing response under dynamic loading cycles is improved with increased CT. • A reaction mechanism is proposed using mineralogical composition of CT and SEM-EDS. • CT with layered NCB/C-A-S-H behaves as ‘functional micro-aggregate’, promoting conductive paths.