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Admixtures - environmental aspects

There are many admixture types that improve the fresh and hardened properties of concrete. For example, plasticisers increase fluidity without the loss of physical performance, which would occur with the addition of more water. Less vibration is then needed to compact the concrete on site or in precast works. Direct contact between operatives and fluid concrete is reduced and there are lower noise levels on site.

This has health and safety benefits and improves the working environment. Water-reducing admixtures lower the water requirement of a concrete, yet retain fluidity, while improving strength and durability. Cement content can be optimised so the impact on the environment is lessened.

Some admixtures are synthetic products derived from petrochemicals. Many others (over 50% in the UK) are derived from the waste-products of paper manufacturing that would otherwise cause environmental disposal problems. Admixtures are used in small amounts relative to the volume of concrete they treat, but can significantly reduce the effect of concrete on the environment.

For further information see “Concrete and the Environment”, published in CONCRETE in September 2001, pp39–46. Copies are available as a free download from the Members Area of the Concrete Society web site.

Acknowledgement: The Concrete Society

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TR18 A guide to the selection of admixtures for concrete