Portland Cement is a type of cement, not a brand name. Many cement companies in iran make Portland Cement.To find out more about what concrete is made of, concrete mix designs, admixtures, and water to cement ratios. Portland cement, the basic ingredient of concrete, is a closely controlled chemical combination of calcium, silicon, aluminum, iron and small amounts of other ingredients to which gypsum is added in the final grinding process to regulate the setting time of the concrete.
NATURAL GYPSUM STONE
Limestone, sedimentary rock composed mainly of calcium carbonate (CaCO3), usually in the form of calcite or aragonite. It may contain considerable amounts of magnesium carbonate (dolomite) as well; minor constituents also commonly present include clay, iron carbonate, feldspar, pyrite, and quartz. It is used in fertilizers, cement industry, poultry feed, etc.