Concrete is the most used construction material in the world with approximately 14 billion m3 used worldwide each year. Up to 90% of the greenhouse gas emissions (GHGs) in the production of concrete are created in the manufacture of Portland cement, which is currently accountable for 8% of all global emissions, and this is expected to rise by 25% by 2050. Per kilogram, concrete has a relatively low embodied carbon and cost compared to steel, whilst also providing high strength and durability, making it an effective and accessible construction material. Due to the vast quantities of concrete used globally, reductions in the carbon factors we use can have a significant global impact, but efficient design choices have real potential to be the most effective way of reducing construction’s carbon footprint. Note that by reducing the assumed carbon factors of concrete during early design stages, this reduces the incentive to do leaner designs.
The greenhouse gas emissions (referred to in this document as ‘carbon’) and the carbon factor (the quantity of greenhouse gases emitted per kg of material) for concrete can vary depending on raw material extraction, processing and manufacturing techniques, supplementary cementitious materials, transportation mode and distance, concrete strength, consistence (workability), and use of water and (super)plasticisers.
We need to understand the carbon emissions associated with the different stages of the concrete manufacturing process, and work collaboratively with contractors, clients and suppliers to meet increasingly critical carbon targets to ensure that the impact of our decisions is felt throughout the supply chain.
This document sets out the factors stage by stage that contribute towards the emission of carbon through the whole life cycle of concrete used for buildings and infrastructure. It will also highlight the potential route to decarbonising the production of concrete through identifying the carbon journeys of the principal constituents, which include:
• Portland cement
• Supplementary cementitious materials (additions)
• Aggregates (fine and coarse)
Using less material as an industry is fundamental to reducing emissions. At present there are no solutions that work at an industry, as opposed to project, scale to significantly reduce the carbon intensity of concrete. This paper aims to provide the reader with information on the status of the industry and best practice, so that they can understand the impact of their design choices and avoid greenwashing.