Abstract: A low cost cement composition that can be admixed with water and hydrothermally closed cured to give acid-resistant products of high compressive strength consisting essentially of, in parts by weight, 1 to 1.5 parts of a calcium oxide material containing at least about 60% CaO, 10 to 15 parts of pozzolanic material containing at least about 30% by weight amorphous silica, and 0.025 to 0.075 parts by weight of an alkali metal catalyst and building materials made therefrom as well as the method of making such building materials by closed curing.