Concrete plays a critical role in shaping the built environment and it also plays a significant role in the global carbon cycle. While cement manufacturing is known to generate CO₂ emissions, concrete itself has the ability to reabsorb carbon dioxide over its lifetime through a natural process called carbonation. This process turns hardened concrete into a meaningful carbon sink, counterbalancing a portion of the emissions associated with cement production.
However, concrete and cement are often mistakenly treated as interchangeable terms. Cement and concrete are not the same thing. Cement is a fine powder that acts as the binding ingredient, made from limestone, clay, and other materials that are heated and ground into a powdered material.
Concrete is the finished building product, created by mixing cement with water, sand, and aggregates like gravel or crushed stone. When cement reacts with water, it hardens and binds the materials together. This forms the durable, long-lasting concrete used in roads, bridges, and buildings. Many critiques of “concrete emissions” miss this distinction, resulting in misunderstandings about concrete’s true environmental footprint and long-term sustainability benefits.
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The True Environmental Impact of Concrete

The CO₂ emitted during cement manufacturing can be measured with high precision. What is less commonly recognized is the amount of carbon sequestered by concrete structures, pavements, and demolition materials throughout their entire life cycle.

Research shows that concrete’s carbonation potential is substantial. A study by Xi et al., Substantial Global Carbon Uptake by Cement Carbonation, found that 43% of total cement process emissions from 1930–2013 have already been reabsorbed through carbonation (excluding emissions from fossil fuels used in manufacturing). This demonstrates that concrete functions as a significant global carbon sink, helping to reduce the net CO₂ impact of the built environment.

Because of the scale at which concrete is produced and used worldwide, this natural CO₂ uptake represents a major, and often overlooked, component of sustainable construction.

Why Carbonation Matters for Life Cycle Assessment (LCA)

Accurate Life Cycle Assessment (LCA) is essential for evaluating the environmental performance of building materials. Without incorporating CO₂ uptake through carbonation, the industry risks overestimating the net carbon footprint of concrete.
Concrete carbonation should be included in all comprehensive LCA methodologies because it:
  • Provides a more accurate representation of concrete’s total environmental impact
  • Helps identify opportunities to optimize mix designs for enhanced sustainability
  • Supports low-carbon construction practices and regulatory compliance
  • Informs long-term strategies for carbon reduction within the built environment
More inclusive and scientifically grounded emission calculations are needed to reflect concrete’s actual role in carbon capture, a factor crucial for policymakers, engineers, and sustainability professionals.

CalPortland’s Research on Carbon Capture

CalPortland is actively advancing understanding of the carbonation process and its implications for sustainable construction. Our research teams are studying:

  • The rate of CO₂ uptake across different concrete applications
  • Variables that influence carbonation over decades of service life
  • How carbonation can be incorporated into next-generation LCA models
  • Opportunities to optimize materials to enhance carbon sequestration

Watch the Project Carbonation video to learn how CalPortland researchers are improving carbon accounting and strengthening sustainable design practices in the cement and concrete industries.

Building a More Sustainable Future Together

Sustainability is a shared responsibility, and CalPortland is committed to leading the way. Through innovation, investment, and a dedication to environmental leadership, we are creating construction materials that strengthen communities today and protect the planet for generations.

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