The water reducing properties of solutions containing small amounts of sodium n-dodecylbenzene-sulfonate and acetone are studied. Water reductions up to 28% are obtained in mortars composed by 30% cement and 70% graded sand. Sorptivity coefficients vary between 78 and 380 g m-2 s-1 2 (no admixture: 744 g m-2 s-1 2). Slump loss rates of mortars with admixture are similar to those of the admixturefree ones. Compressive strength after 28 days is roughly 50% higher for the mortars with admixture. Surface tension measurements are used to explain the unexpected efficiency of these solutions. © 1994.245987992Aignesberger, Kern, Use of Melamine-Based Superplasticizer as a Water Reducer (1981) Developments in the Use of Superplasticizers, , V.M. Malhotra, 21st Edn., ACI Publication SP-68, American Concrete Institute, DetroitTaylor, (1990) Cement Chemistry, , Academic Press, LondonCollepardi, Corradi, Valente, Influence of Polymerization of Sulfonated Naphtalene Condensate and its Interaction with Cement (1981) Developments in the Use of Superplasticizers, , V.M. Malhotra, 21st Edn., ACI Publication SP-68, American Concrete Institute, DetroitMehta, (1986) Concrete: Structure, Properties and Materials, , Prentice-Hall Inc, New JerseyHampton, Extended Workability of Concrete Containing High-Range Water-Reducing Admixture in Hot Weather (1981) Developments in the Use of Superplasticizers, , V.M. Malhotra, 21st Edn., ACI Publication SP-68, American Concrete Institute, DetroitBrazilian Patent 9.104.382 (1991)Hall, Water Sorptivity of Mortars and Concrete (1989) Mag. Concr. Res., 41 (147), pp. 51-61Muhua, Roy, An Investigation of the Effect of Organic Solvents on the Rheological Properties and Hydration of Cement Paste (1987) Cem. Concr. Res., 17 (6), pp. 983-994