A method includes adding (i) a comb polymer and (ii) a plasticizer to a mineral binder composition comprising swellable clays. The comb polymer includes: at least one poly(alkylene oxide) side chain-bearing monomer unit without ionic groups, optionally at least one cationic monomer unit, optionally at least one anionic monomer unit, and optionally, at least one non-ionic monomer unit, wherein a molar ratio of the cationic monomer units to the side chain-bearing monomer units is equal to or less than 10, a molar ratio of the anionic monomer units to the side chain-bearing monomer units is less than 1, and a molar ratio of the non-ionic monomer units to the side chain-bearing monomer units is less than 5.