Summary
UCLA researchers have developed a method for replacing a substantial portion of ordinary Portland cement (OPC) by using direct carbonation of brucite (Mg(OH)₂) in concrete mixtures, enabling lower-carbon concrete products produced under near-ambient conditions with cost-competitive engineering performance.
Background
Concrete production using OPC is highly energy-intensive and a major contributor to global CO₂ emissions (~9 %). Production, clinker formation, and grinding steps require high heat and generate large emissions. There is a growing need for cementation methods that reduce reliance on OPC, incorporate CO₂ utilization (sequestration), and lower embodied carbon intensity without sacrificing strength, durability, or compatibility with existing concrete production infrastructure.
Innovation
This invention introduces concrete mixtures in which 20-90 % (by mass) of a binder component is composed of brucite combined with cement replacement materials (e.g. fly ash, slag, recycled materials), with OPC reduced to 5-50 % of the binder. After casting, the concrete mixture is cured and then carbonated by exposure to gaseous CO₂ (dilute CO₂ from flue gas streams, e.g. 2-30 % CO₂ by volume), under moderate temperature (e.g. ~20-90 °C), relative humidity, and low pressure. The carbonation reaction converts brucite into stable magnesium carbonate hydrates (such as nesquehonite, hydromagnesite, artinite, dypingite, etc.), which act as cementitious phases, leading to solidification and strength gain. The process can be integrated into existing concrete or precast concrete production, offering reduced embodied carbon intensity while maintaining engineering and functional performance similar to traditional concrete.
Advantages
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High OPC replacement: Up to ~50-90 % of OPC in the binder can be replaced by brucite + replacement materials.
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Significant CO₂ sequestration: Brucite carbonation captures CO₂ and forms stable magnesium carbonate hydrates under mild conditions.
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Lower embodied carbon intensity (eCI): Potential to cut eCI of concrete components by at least 50 % compared to conventional OPC-based concrete.
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Compatibility with existing infrastructure: Can be incorporated into conventional concrete plants, precast operations, masonry units with minimal retrofit.
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Operates near ambient pressure and moderate temperatures: Reduces energy input and cost compared to high-temperature / high-pressure carbonation routes.
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Flexible mixture design: Use of various cement replacement materials, aggregates, admixtures, filler types allows tailoring of performance and cost.
Potential Applications
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Low-carbon concrete for construction (masonry blocks, precast panels, structural members).
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Precast concrete product manufacturing seeking embodied carbon reduction.
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Infrastructure projects aiming for carbon footprint certification or carbon neutral goals.
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Concrete repair or overlay materials where environmental performance is valued.
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Concrete in industrial facilities where CO₂ capture or utilization can be sourced from onsite flue gases.
Patent
US 2024/0199456 A1 — Direct brucite carbonation for cementation
Direct brucite carbonation for cementation (US20240059615A1)
Priority Date: June 30, 2022; Application Filed: June 30, 2023; Publication Date: February 22, 2024. Google Patents