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-1 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.245987992