Admixtures are chemicals added in very small amounts to the concrete to modify the properties while the concrete is still fluid and also after it has hardened and is in service. The quantity added is less than 0.2% and usually less than 0.1% of the concrete weight but even at this low level, admixtures have a very significant effect on the concrete properties. These effects include:
- Reducing the embodied carbon of concrete - because admixtures are used to both increase workability and reduce the water/cement ratio, and
hence increase strength and reduce permeability of hardened concrete, without increasing cement content.
- Increased fluidity: reduces noise and energy requirements during placing.
- Optimised mix design: reducing embodied carbon dioxide and energy by enhancing the effectiveness of the cement component.
- Reduced permeability: increases the durable life of the concrete.
- Reduced damage from harsh environments: including marine, freeze-thaw and sub zero situations.
- Improved quality: better finish and reduced service life repair.
The admixture manufacturing process has been subject to an environmental inventory that has enabled Environmental Product Declarations (EPD) to be produced covering over 80% of admixture production in the European Union.
These six EPDs can be downloaded free from the Cement Admixtures Association (CAA) website together with additional environmental and sustainability related documents.