Underwater concrete anti-washout admixtures increase the cohesion of the concrete in a way that significantly reduces the washing out of cementitious material and sand from fresh concrete placed underwater. Anti?washout admixtures are often used in conjunction with superplasticisers to produce flowing self-levelling concrete to aid placing and compaction underwater.

The admixtures were developed to provide a higher integrity of concrete placed underwater and to reduce the impact that the wash-out material can have on the marine environment. They are suitable for deep underwater placement, in inter-tidal zones and in the splash zone and other situations where water movement could wash out cement and other fine material.

Note: Not all admixture types are covered by EN 934. BS 8443:2005 Specification for establishing the suitability of special purpose concrete admixtures, covers the following; underwater concrete admixtures, shrinkage reducing admixtures, corrosion inhibiting admixtures, pumping aids, segregation reducing admixtures, foaming admixtures, semi-dry concrete admixtures.