The purpose of this standard is to describe an operating procedure to determine the content of reducing substances (called, in this standard, reducing power of additives) in the fraction soluble in distilled water of additives for concrete, mortars and pastes. This test allows us to know the presence of sugars in the additives, which could influence the setting or hardening speed of a paste, a mortar or a concrete. This standard should not be applied to additives that have substances capable of giving, due to alteration in the course of the treatments described in this standard, reducing products capable of reacting with the FEHLING liquid (eg certain cellulose derivatives).