The invention relates to a dry additive for hydraulic binders, and to the production and use thereof. The solid additive is characterized by comprising a liquid additive (1) disposed in a microporous carrier (2). The inventive additive allows for the formulation of hydraulically curing compositions (3) which have a substantially better storage stability than the corresponding hydraulic composition to which the liquid additive (1) was directly added. The invention also relates to a method for the rehabilitation of cured hydraulic compositions such as concrete, and therefore to the possibility of corrosion protection of concrete steel in already cured hydraulic compositions.