Incorporating supplementary cementitious materials (SCMs) and alternative aggregates promotes cleaner production of cement-based materials; however, optimizing their coupled effects on mechanical and environmental performance remains a key challenge. This study assesses the valorization of copper slag (CS), a massive industrial mining by-product, simultaneously as an SCM and an artificial fine aggregate (AFA) in the development of mortar mixtures with better performance and lower embodied carbon. Specifically, CS partially replaced Portland cement (PC) at 0% and 15% by volume, while natural fine aggregate (NFA) was substituted with AFA at volumetric replacement levels of 0%, 20%, 40%, and 60%. Mortar performance was systematically evaluated in the fresh state via workability and in the hardened state through water absorption, alongside short- and long-term compressive and flexural strength development. Furthermore, a cradle-to-gate life cycle assessment (LCA), expressed in terms of embodied carbon (EC) emissions, was executed to assess the environmental performance of the mixtures. The results indicate that incorporating CS as both SCM and AFA improved mortar workability by up to 30.9% compared to the reference mortar mixture (100% PC and 100% NFA). At 7 days, compressive strength decreased by 4% to 20% relative to the reference mortar. However, long-term performance improved substantially; at 330 days, mixtures with 15% CS–0% AFA and 15% CS–60% AFA achieved average compressive strengths of 42.9 MPa and 53.1 MPa, respectively, outperforming the reference mortar (42.1 MPa) by up to 26%. The cradle-to-gate embodied-carbon assessment showed that CS incorporation reduced product-stage emissions, although outcomes depended on transport distance and strength development. EC ranged from 369.8 to 438.0 kg CO₂e/m³. When transport was included, EC decreased by approximately 14%, while 330-day strength-normalized EC decreased by 29.6–32.1% relative to the reference mixture. Overall, CS-based mortars improved fresh-state properties, enhanced long-term mechanical performance, and reduced product-stage embodied carbon, demonstrating their potential for cleaner production.

Alkali-activated mortars (AAMs) have emerged as sustainable alternatives to conventional hydraulic cement (HC) matrices produced with natural sand. In this context, interest in the valorization of industrial by-products to develop eco-efficient construction materials has gained crucial academic and industrial attention. This study investigates the feasibility of producing AAMs incorporating copper slag (CS) as an artificial fine aggregate (AFA) to partially or completely replace natural sand. Moreover, the binder matrix was formulated using 80% CS and 20% HC as precursors, activated with different alkaline solutions (Na₂SiO₃ + NaOH) at activator-to-precursor mass ratios ranging from 0.15 to 0.35. Concurrently, CS was incorporated as AFA at volumetric replacement levels of 0%, 25%, 50%, 75%, and 100%. The AAMs were evaluated in terms of workability, physical performance (i.e., bulk density, water absorption, and void content), and mechanical performance. The results demonstrate that the workability of the AAMs increased with higher AFA dosages, reaching a maximum improvement of 23.8% compared with the AAM without AFA. The bulk density of the AAMs increased monotonically with increasing AFA content (consistent with the higher density of AFA with respect to natural sand), whereas water absorption and void content decreased progressively. Although all AAMs exhibited significantly lower compressive strengths than M1 at 7 and 28 days, the differences progressively decreased with curing age. At 56 and 90 days, M5 and M6, incorporating 75% and 100% AFA, respectively, achieved mean compressive strengths that were not statistically different from those of M1, indicating that the mixtures with the highest AFA contents maintained later-age mechanical performance within the variability of the conventional reference mortar. The study demonstrates the feasibility of the synergistic utilization of CS as both precursor and AFA in AAMs. This dual-pathway valorization closes materials loops and advances circular economy principles within the construction sector.