Decarbonizing Concrete: Ultra-Low-Carbon Pathways and Policy Integration

Abstract

Concrete production is responsible for roughly 7–8% of global CO₂ emissions, making the material an urgent climate priority. This narrative review investigates whether—and how—concrete can achieve ultra-low-carbon (≥ 50% reduction) or carbon-negative (net CO₂ uptake) performance by 2035. Peer-reviewed literature dated January 2020 to April 2025 was retrieved from Scopus, Web of Science, and Engineering Village, then grouped into six pathways: cement-manufacturing decarbonization, supplementary cementitious materials (SCMs), alkali-activated/geopolymer binders, CO₂ capture and mineral carbonation, bio-mediated carbonation, and AI-driven mix optimization, together with policy and durability evidence. Using SCMs like fly ash, slag, and calcined clay can usually reduce carbon emissions by 30–80%; geopolymers and other alternative binders can lower emissions by 20–60% when using eco-friendly activators; and new CO₂-curing technologies, such as cement-free block systems, have shown they can actually take in more CO₂ than they produce, with reductions as high as –11.7 kg CO₂ per cubic meter by turning captured CO₂ into solid minerals. Techno-economic studies show these measures become cost-competitive when paired with incentives like the U.S. 45Q credit (USD 85 t1CO₂). Durability data indicate most low-carbon concretes equal or exceed conventional mixes in chloride, sulfate, and freeze–thaw resistance, though long-term field evidence remains limited. Coordinated standards updates (e.g., ASTM C1709-18), “Buy Clean” procurement, and open emissions databases—coupled with large-scale demonstrations and harmonized life-cycle assessment—are critical to mainstreaming truly sustainable concrete.