An admixed cement composition comprising: - a cement composition comprising: - from 20 to 64 weight % clinker, - from 5 to 60 weight % activated clay, - from 0 to 35 weight % limestone, - from 0 to 10 weight % calcium sulfate, the proportions of clinker, activated clay, limestone and calcium sulfate being relative to the dry weight of the cement composition and - an admixture comprising a polymer comprising units of following formulas and: where: - R 1 and R 2 are each independently a hydrogen or a methyl, - R 3 is a hydrogen or a group of formula -COO 1/m - R 4 is a group of formula -(CH 2) p -(OAlk) q -R 5 where: - p is 1 or 2, - q is an integer of 3 to 300, - the Alk in each OAlk unit of the group -(OAlk) q - is independently a linear or branched alkylene having 2 to 4 carbon atoms, - R 5 is -OH or a linear or branched alkoxyl having 1 to 4 carbon atoms, - R 11 and R 12 are each independently a hydrogen or a methyl, - R 13 is a hydrogen or a group of formula -COO 1/m, - M is H or a cation of valence m, - when M is H, m is 1 and when M is a cation, m is the valence of the cation M, - a is a number from 0.05 to 0.25, such that (100 x a) represents the molar percentage of units of formula within the polymer, and - b is a number from 0.75 to 0.95, such that (100 x b) represents the molar percentage of units of formula within the polymer, the proportion of polymer in the admixture being from 0.001 weight % to 5 weight %, in particular from 0.005 weight % to 1 weight %, preferably from 0.01 weight % to 0.2 weight % relative to the dry weight of the cement composition. - a cement composition comprising: - from 20 to 64 weight % clinker, - from 5 to 60 weight % activated clay, - from 0 to 35 weight % limestone, - from 0 to 10 weight % calcium sulfate, the proportions of clinker, activated clay, limestone and calcium sulfate being relative to the dry weight of the cement composition and - from 20 to 64 weight % clinker, - from 5 to 60 weight % activated clay, - from 0 to 35 weight % limestone, - from 0 to 10 weight % calcium sulfate, - an admixture comprising a polymer comprising units of following formulas and: - R 1 and R 2 are each independently a hydrogen or a methyl, - R 3 is a hydrogen or a group of formula -COO 1/m - R 4 is a group of formula -(CH 2) p -(OAlk) q -R 5 where: - p is 1 or 2, - q is an integer of 3 to 300, - the Alk in each OAlk unit of the group -(OAlk) q - is independently a linear or branched alkylene having 2 to 4 carbon atoms, - R 5 is -OH or a linear or branched alkoxyl having 1 to 4 carbon atoms, - p is 1 or 2, - q is an integer of 3 to 300, - the Alk in each OAlk unit of the group -(OAlk) q - is independently a linear or branched alkylene having 2 to 4 carbon atoms, - R 5 is -OH or a linear or branched alkoxyl having 1 to 4 carbon atoms, - R 11 and R 12 are each independently a hydrogen or a methyl, - R 13 is a hydrogen or a group of formula -COO 1/m, - M is H or a cation of valence m, - when M is H, m is 1 and when M is a cation, m is the valence of the cation M, - a is a number from 0.05 to 0.25, such that (100 x a) represents the molar percentage of units of formula within the polymer, and - b is a number from 0.75 to 0.95, such that (100 x b) represents the molar percentage of units of formula within the polymer,