Carbon mineralisation in concrete is a process where carbon dioxide permanently transforms into solid carbonate minerals within the concrete structure. This technology turns CO2 into a valuable resource that strengthens concrete while storing carbon permanently. The process occurs during concrete curing, creating calcium carbonates that enhance material properties and reduce cement requirements.
What is carbon mineralisation in concrete and how does it work?
Carbon mineralisation in concrete is the permanent conversion of carbon dioxide gas into solid carbonate minerals within the concrete matrix. This process chemically binds CO2 into the concrete structure, transforming it from a greenhouse gas into a stable, solid mineral form that remains locked in the material.
The mineralisation process follows several key stages:
- Chemical reaction: The CO2 reacts with calcium hydroxide and other calcium-bearing compounds present in the concrete mix
- Crystal formation: The reaction produces solid calcium carbonate crystals that fill pore spaces and integrate into the concrete’s binding matrix
- Permanent integration: The carbonate minerals become structurally bonded within the concrete, ensuring the CO2 cannot escape back into the atmosphere
This molecular-level transformation creates a permanent carbon storage solution while simultaneously improving the concrete’s properties. The mineralisation requires controlled conditions including adequate moisture, proper temperature, and precise CO2 exposure timing during curing.
Read more about the chemistry of CO2 curing from our blog.
How does CO2 curing make concrete stronger while storing carbon?
CO2 curing creates a dual benefit by forming calcium carbonate crystals that act as both carbon storage and strength enhancers. The carbon dioxide reacts with calcium compounds during curing to produce ultrafine calcium carbonate particles that serve as nucleation sites for crystal formation and provide additional binding within the concrete matrix.
The strengthening mechanism operates through multiple pathways:
- Nucleation site creation: CO2 produces ultrafine calcium carbonate particles that provide specific locations where crystal formation begins, accelerating the curing process
- Pore space filling: Carbonate crystals fill voids within the concrete matrix, creating a denser and stronger material structure
- Additional binding compounds: The calcium carbonate acts as supplementary binding material beyond traditional cement hydration products
- Bottleneck elimination: CO2 introduction removes common limitations in crystal growth during initial curing hours, allowing faster strength development
The seeding stage initiates this process by establishing abundant nucleation sites through calcium carbonate formation. By providing these growth sites early in the process, CO2 curing enables both carbonates and hydrates to develop more rapidly. This enhanced crystal development not only accelerates strength gain but also ensures permanent carbon storage, as the CO2 becomes chemically bound within the concrete matrix and cannot release under normal conditions throughout the concrete’s lifespan.
What’s the difference between traditional concrete curing and CO2 mineralisation?
Traditional concrete curing relies on water-based hydration reactions with cement, while CO2 mineralisation adds carbon dioxide to create additional binding compounds through carbonation reactions. These approaches differ significantly in their mechanisms, timelines, and outcomes.
Conventional methods use external steam or heated chambers to maintain conditions, while CO2 systems provide precise control over temperature, humidity, carbon dioxide flow, pressure, and timing. A modern CO2 curing system automatically manages these variables to optimise both carbon storage and concrete quality, making the process reliable and repeatable for commercial applications.
