Life Cycle Assessment of Ternary Cement Production Based on Calcined Clay and Marble Residue

The cement industry has been seeking strategies to ensure the circularity of materials through the incorporation of solid waste into its processes, driven by the environmental challenges associated with cement production, such as high CO2 emissions and resource consumption. In this context, marble residue (MR) has been investigated for application in cementitious materials, including as a partial cement substitute, which also mitigates MR deposition as an inert waste in landfills. Although its technical feasibility has shown promising results, environmental justification is still necessary to validate this technology. This research presents a Life Cycle Assessment (LCA) of MR as a substitute for limestone filler in ternary cement production, promoting circular economy principles. The environmental impacts of three formulations were compared: Ordinary Portland Cement (OPC), used as the reference; limestone calcined clay cement (LC3), composed of calcined clay and limestone filler; and LC3-R, which incorporates 15% MR in place of limestone filler. The cradle-to-gate LCA included raw material extraction through to cement production, using OpenLCA (v2.3) and the Ecoinvent database (v3.6). The impact categories analyzed included abiotic depletion (ADP), abiotic depletion of fossil fuels (ADP-ff), global warming potential (GWP 100a), ozone layer depletion (ODP), human toxicity potential (HTP), and acidification potential (AP). Results showed that LC3-R had the lowest environmental impacts, with reductions up to 39% compared to OPC and 11% compared to LC3. A sensitivity analysis was conducted for environmental and economic dimensions to assess the influence of MR transportation distances in the LC3-R context. The LC3-R formulation remained environmentally viable up to an additional 400 km compared to OPC, and up to 100 km compared to LC3, being also competitive in the economic dimension. The results highlight the benefits of incorporating marble residue into LC3 cement, contributing to environmental impact reduction and promoting resource efficiency within a circular economy approach.