Comparative Cradle-to-Gate Carbon Footprint Assessment of Selected Cementitious and Alkali-Activated Composites

The construction sector contributes substantially to greenhouse gas emissions, largely because of Portland cement clinker production in cementitious composites. This study presents a cradle-to-gate life-cycle assessment of selected cementitious and alkali-activated concretes and mortars, with particular focus on global warming potential and potential environmental trade-offs. The assessment was performed using openLCA 2.6.2 and Microsoft Excel, with inventory data from BAFU-2025 Version 2 and impact categories calculated using the CML-IA baseline method. Two material groups were evaluated per 1 m3: six concretes based on CEM I, CEM II/B-V, CEM III/B, ground granulated blast-furnace slag, fly ash, or a slag–fly-ash combination, and four mortars based on CEM I, CEM III/C, CEM VI (S-LL), or alkali-activated slag. CEM III/B concrete reduced global warming potential by 54.8% relative to CEM I, while the slag–fly-ash alkali-activated concrete achieved a 71.9% reduction. CEM III/C mortar achieved the lowest mortar value, 76.6% below CEM I. Selected alkali-activated systems, nevertheless, showed higher toxicity-, ecotoxicity-, and resource-related results. Within the adopted cradle-to-gate boundary and volumetric functional unit, the findings show that binder selection should be evaluated across several impact categories, rather than by carbon footprint alone. The specific contribution is a recipe-level comparison of six concretes and four mortars under one consistent cradle-to-gate CML-IA framework, testing whether the GWP ordering of the ten selected recipes is reflected in ten other midpoint categories. These percentages describe production-stage burdens per unit volume; they do not demonstrate equivalent strength, durability or service life.