A copolymer includes a main hydrocarbon chain and side groups including carboxylic groups and polyoxyalkylate groups. The copolymer further includes gem-bisphosphonate groups. The copolymer can be included in an admixture for suspensions of mineral particles and in a composition of mineral particles. The copolymer can also be used for fluidifying and maintaining fluid, suspensions of mineral particles and for reducing the sensitivity of hydraulic compositions to clays and alkaline sulfates.