Copper tailings recycling in cement-based composites: A deterministic LCA approach accompanied by microstructure, mechanical, thermal and non-destructive tests

Abstract

Innovative approaches to sustainable building materials are needed due to the cement industry's high carbon footprint and the environmental management of massive amounts of copper tailings (CT) from mining operations. Using a comprehensive approach, this study aims to evaluate the thermal-mechanical performance and ecological sustainability of CT, a high-silica (>79 %) and distinctly bimodal grain-distribution material from Artvin-Murgul, as a pozzolanic additive in cement-based composites. To achieve this, mortar series were created in which CT was added to cement at weight percentages ranging from 0 % to 15 %. Mechanical, thermal, microstructural, and pozzolanic activity analyses were employed to evaluate the performance of the samples. A cradle-to-grave Life Cycle Assessment (LCA) employing the EF 3.1 method in compliance with ISO 14040/44 standards was also used to evaluate environmental performance. With a pozzolanic activity index of 76.2 %, the results verified that CT is a pozzolanic material. The 28-day compressive strength was maintained at 52.5 MPa, with the best performance from the 5 % CT replacement. The composite's higher density, however, resulted in a slightly lower specific strength compared to the control sample, underscoring the trade-off between mass efficiency and environmental advantages. Additionally, there was a 2.1 % increase in flexural strength (7.17 MPa). The success of the pozzolanic reaction has been chemically verified through microstructural analyses. The weak Ca(OH)2 phase was consumed by the 5 % CT addition, which significantly decreased the Ca/Si ratio in the matrix and resulted in a more robust C-S-H structure. According to LCA results, applying 15 % CT resulted in notable improvements in Global Warming Potential (GWP) and all impact categories, particularly acidification and eutrophication. A 12.4 % decrease in net lifecycle GWP was computed, taking carbonation effects into account. In addition to enhancing mechanical performance, this study demonstrates that using CT at the optimal rate offers substantial environmental advantages, as evidenced by LCA. This process effectively turns industrial waste into a valuable, eco-friendly building material