Environment
LC3 (Limestone Calcined Clay Cement)
A low-carbon cement blending calcined clay and limestone to replace about half of conventional clinker, cutting CO₂ emissions by up to roughly 40%.
Definition
Limestone Calcined Clay Cement (LC3) is a ternary blended cement in which calcined clay and ground limestone jointly substitute around 50% of Portland clinker (typical LC3-50 formulation: 50% clinker, 30% calcined clay, 15% limestone, 5% gypsum). It achieves roughly 30–40% lower CO₂ emissions than ordinary Portland cement with comparable mechanical performance, and can be produced in existing plants.
References
Definition, up-to-40% CO₂ reduction, low-grade clay suitability, plant compatibility
50% clinker substitution, EN 197-5:2021 inclusion, performance parity
Overview
What it means
Clinker production is the source of most cement emissions (cement accounts for roughly 8% of global CO₂), so deep clinker substitution is the sector's principal near-term decarbonisation lever. Calcined clay fires at about 800 °C rather than clinker's ~1450 °C, and both clay and limestone are abundant — including low-grade clays — making LC3 scalable where traditional substitutes (fly ash, slag) are declining.
LC3 was recognised in European standard EN 197-5:2021 (cement type II/C-M) and shows strong chloride resistance, aiding durability in coastal structures.
How it is used
LC3 is entering commercial production, promoted by the EPFL-led LC3 Project with Swiss development funding, and is assessed in procurement, codes and life-cycle assessments as a Portland-cement alternative.
Why it matters
It is one of the few immediately scalable, cost-effective routes to deep cuts in construction-sector emissions.
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