The present invention provides compositions for use as stable additive concentrates, such as aqueous solutions or powders, in cement admixtures comprising i) one or more nonionic or substantially nonionic vinyl or acrylic brush polymers having pendant or side chain polyether groups and having a weight average molecular weight of from 140,000 to 50,000,000, ii) one or more aromatic cofactors containing one or more phenolic groups or, in combination, one or more aromatic groups with at least one sulfur acid group, preferably, a branched aromatic cofactor; and iii) one or more polycarboxylate ether copolymer water reducers containing carboxylic acid or salt groups and having polyether side chains and a weight average molecular weight of from 5,000 to 100,000.