Comparative Environmental Evaluation of Conventional, Low-Clinker and Alkali-Activated Concretes and Mortars

Clinker substitution can reduce cradle-to-gate global warming potential (GWP), but does not establish improvement in resource depletion, toxicity, or ecotoxicity. This life cycle assessment (LCA) compares six concrete and four mortar inventory models per 1 m3 at the production gate using the Swiss Federal Office for the Environment (BAFU) inventory and the CML baseline life cycle impact assessment method (CML-IA), developed by Leiden University’s Institute of Environmental Sciences (CML). Under the original provider mappings, AAC-3 (slag–fly ash alkali-activated concrete) had the lowest modeled GWP within the concrete group at 78.2 kg CO2 eq m−3, 71.9% below concrete CEM I (278.2 kg CO2 eq m−3). CEM III/C mortar had the lowest modeled GWP within the mortar group at 101.2 kg CO2 eq m−3, 76.6% below mortar CEM I (433.1 kg CO2 eq m−3). These are separate 1 m3 production gate results using the original activator exchanges, a common freight exchange, and no additional curing energy; they do not establish performance equivalence. CEM II/B-V concrete was below its reference in all eleven categories, whereas activated models exceeded their references in seven or eight. Clinker dominated GWP in the CEM I reference systems; natural gas was the largest positive GWP process in the activated models (7.8–12.4% of net GWP). The modeled mercury cell, sodium hydroxide and upstream mercury supply processes accounted jointly for 32.3–72.4% of activated system terrestrial ecotoxicity. Activator mappings and precursor allocation remain unresolved, so these results identify the lowest outputs in the original models rather than a validated ranking of materials.