Products with a fluidifying action for mineral pastes and binders

A mineral paste or binder with increased fluidity said increased fluidity accomplished by inclusion of an alkali metal salt of a sulphonated styrene-indene hydrocarbon resin said resin prepared by polymerisation of an aromatic petroleum fraction, derived from vapor cracking, using a Friedel-Krafts catalyst, so as to yield a resin having a KS softening point between 60.degree. and 150.degree. C and a low degree of polymerisation, followed by sulphonation of the styrene-indene hydrocarbon resin in solution to produce a product having a content of unsulphonated material of less than 10%, with subsequent neutralization with an alkali.