This European Standard defines and specifies the requirements and conformity criteria for admixtures for use in cement based masonry mortar. It covers two types of admixtures, long term retarding and air entraining/plasticising which are used in ready-mixed and site made masonry mortars. Provisions for the use of admixtures for masonry mortar are not part of this European Standard but are covered by EN 998-1 and EN 998-2.