The approximate percentage of gypsum in Portland cement is

Weight percentage of silica in portland cement is

Cement is one of the most important building material of the present time. It is a dirty greyish heavy powder containing calcium aluminates and silicates. The important raw materials neede for the manufacture of cement are limestone, clay and gypsum. the main step in the manufacture of cement is the heating of raw meal or slurru in the rotary kiln at a very high temperature 1400-1600^(@)C . Finally 2% or 3% gypsum is added. When cement is mixed with water and left as such for sometime, it becomes a hard mass. This is known as setting of cement. It is believed that varous aluminates and silicates present in the cement form hydrates with water which seperate in the form of gel. the gel formed start losing water partly by evaporation and partly by forming hydrates with unhydrated constituents. this results in the formation of a hard mass. The percentage of lime in portland cement is approximately

Weight percentage of gypsum in cement is approximately

The average composition of portland cement is