本发明提供在暴露于高温之后具有减少收缩之以硫酸钙为主的产物，该产物包含石膏、火山灰源材(譬如介于4-27wt%之间的份量)与一金属盐添加剂(介于0.5与10wt%之间的份量)。该火山灰源材可选自一高岭土黏土材料、飞灰、谷壳灰、硅藻土、火山灰与浮石、微-氧化硅、硅灰与硅酮油。该金属盐添加剂可为一金属盐，其可在介于300-500℃之间的温度分解，以产生金属氧化物，譬如硝酸镁。

The present invention provides calcium sulphate-based product having reduced shrinkage after exposure to high temperatures, the product comprising gypsum, a pozzolan source (e.g. in an amount between 4-27 wt%) and a metal salt additive (in an amount between 0.5 and 10 wt%). The pozzolan source may be selected from a kaolinitic clay material, fly ash, rice husk ash, diatomaceous earths, volcanic ashes and pumices, micro-silica, silica fume and silicone oil. The metal salt additive may be a metal salt which decomposes between a temperature of 300-500 DEG C to yield a metal oxide, e.g. magnesium nitrate.