The present invention relates to a heat storage composition comprising 60-98% by weight of sodium sulfate decahydrate and 1-10% by weight of one or more superabsorbents 1-10% by weight of one or more nucleators and 0-20% by weight of one or more water-soluble salts, based in each case on the heat storage composition, said superabsorbent comprising, in polymerized form, a) at least 50 mol %, based on the superabsorbent, of one or more monoethylenically unsaturated monomers comprising acid groups, the degree of neutralization of the monoethylenically unsaturated monomers comprising acid groups being 15 to 85 mol %, and b) 0.015 to 0.1 mol %, based on the total amount of monomers, of at least one crosslinker, to a process for production thereof and to the use thereof as a heat-storing building material and as a heat storage element for motor vehicles, walls of transport vessels or other heat storage vessels.