The present invention consists in the use, in a process of manufacture of a composition with a water and hydraulic binder base, of a rheological additive characterised in that it is an emulsion of at least one non-cross-linked copolymer, consisting of: a) (meth)acrylic acid, b) alkyl(meth)acrylate having 1 to 25 carbon atoms, c) a monomer of formula R1—(R2O)m—R3, in which: R1 designates a radical containing a polymerisable unsaturated group, R2O designates an alkylene oxide group having 1 to 6 carbon atoms, m is an integer between 20 and 30, preferentially between 23 and 27, and is very preferentially equal to 25, R3 designates a linear or branched alkyl chain having 28 to 33 carbon atoms, preferentially 30 to 33 carbon atoms, and very preferentially having 32 carbon atoms. The invention also concerns the formulations thus obtained.