surface-active agent

(materials) A soluble compound that reduces the surface tension of liquids, or reduces interfacial tension between two liquids or a liquid and a solid. Also known as surfactant.

1. In unhardened mixtures of concrete, an additive which has the ability to modify the surface tension of the mixing water, thereby facilitating the wetting and penetrating action of the water, and/or assisting the emulsifying, dispersing, solubilizing, foaming, or frothing of other additives.
2. Same as surfactant.