The present invention refers to a settable mixture comprising (i) a water absorbing composition and (ii) an aqueous emulsion of organic polymer or (iii) dispersible organic polymer, wherein the water absorbing composition (i) contains inorganic ingredients which are capable to react with water and the water absorbing composition (i) contains at least 13 weight % lime and at least 5 weight % of a cementitious composition of which components form ettringite during the absorption of water and wherein the amount of the aqueous emulsion of organic polymer (ii) in relation to (i) is such as to provide a ratio of combined weight of polymer solids to combined weight of ingredients which are capable to react with water of from 0.5:1 to 10:1, preferably 1:1 to 4:1 and wherein the amount of dispersible organic polymer (iii) in relation to (i) is such as to give a ratio of combined weight of polymers to combined weight of ingredients which are capable to react with water of from 0.5:1 to 10:1, preferably 1:1 to 4:1.