A cement composition for use in an oil or gas well, the cement composition comprises: a calcium aluminate cement; water; an organic acid; and a polymeric mixture comprising: (A) water; (B) citric acid; (C) a first polymer, wherein the first polymer: (i) comprises a cellulose backbone and carboxymethyl functional groups; and (ii) has a molecular weight of less than 100,000; and (D) a second polymer, wherein the second polymer: (i) comprises a lignosulfonate; and (ii) has a molecular weight of less than 100,000, wherein a test composition consisting essentially of: the cement; the water; the organic acid; and the polymeric mixture, and in the same proportions as in the cement composition has a thickening time of at least 5 hours at a temperature of 300° F. (148.9° C.) and a pressure of 10,000 psi (68.9 MPa).