• The EPAC project is using 7,500m3 of structural concrete with a composition of 75% GGBS (Ground Granulated Blast Furnace Slag), and Slag cement replacement (blast furnace bi-product), in place of 100% Portland Cement.

• The concrete design was based on its radiation shielding properties, high density aggregates & reduced cement content to reduce the risk of thermal cracks.  Specifying this concrete mix enabled the site team to maintain control of the curing temperature to ensure minimal cracking and achieve the specified oven dry density for shielding purposes.

Project Name: Harwell EPAC

Contractor: Mace 

48 Percent Carbon Reduction using 75 Percent GGBS in Structural Concrete

Key Challenges

Due to the nature of the project (essentially a concrete box to house super-bright lasers to produce state-of-the-art 3D X-rays in just 40 seconds), a huge volume of structural concrete is required (7,500m3) in large pour sizes. Concrete is the most widely used man-made material in existence.  Whilst cement – the key ingredient in concrete – has shaped much of our built environment, it also has a massive carbon footprint.  Cement is the source of about 8% of the world’s carbon dioxide (CO2) emissions.  Not only does the production of Portland cement involve quarrying – causing airborne pollution in the form of dust – it also requires the use of massive kilns, which require large amounts of energy.  The actual chemical process of making cement also emits staggeringly high levels of CO2.


The EPAC project specified 7,500m3 of structural concrete with a composition of 75% GGBS (Ground Granulated Blast Furnace Slag) in place of 100% Portland Cement.  OTB (Outside the Box), the concrete consultant, and Hansen’s technical department collaborated with Mace on the final mix design.  Installer: J Coffey