This document explains how we calculate how much CO₂ concrete absorbs from the atmosphere. This information will be used in our building Life Cycle Assessment (LCA) tools and potentially in other concrete-related tools.
What is Concrete Carbonation?
Concrete carbonation is a natural process where CO₂ from the air reacts with the cement in concrete. This reaction creates calcium carbonate (limestone) and helps to lock up some of the CO₂.
How is CO₂ Uptake Calculated?
The amount of CO₂ that concrete can absorb depends on several factors, including:
Cement type: Different types of cement have different amounts of clinker, the main ingredient that reacts with CO₂.
Concrete strength class: The amount of cement in the concrete mix affects how much CO₂ it can absorb.
Exposure conditions: Concrete exposed to rain and humidity will absorb more CO₂ than concrete sheltered from the elements.
To calculate CO₂ uptake, we use a formula based on European Standard EN 16757:2017. This formula takes into account the factors mentioned above.
Streamlined Calculation for Construction Professionals
To make this calculation easier to use, we have:
Streamlined the formula: We have pre-set lifespans (50 and 60 years) to give you a snapshot of CO₂ uptake potential.
Averaged cement content: We used average cement content values for a standard-defined group of concrete strength classes for standard compliance and to minimize selection confusion.
Grouped cement substitutes: We grouped different cement substitutes for standard compliance and to minimize selection confusion.
Key Takeaways for Construction Professionals
Concrete carbonation can help to offset some of the CO₂ emissions from cement production.
The amount of CO₂ that concrete can absorb varies depending on the type of cement, concrete mix, and exposure conditions.
Using the streamlined tables to estimate the CO₂ uptake potential, we have created resources that you can use in your calculations.