How is portland cement made ?

Materials that contain appropriate amounts od calcium compounds , silica m alumina and iron oxide are crushed and screened and placed in a rotating cement kiln . Ingredient used in this process are typically materials such as limeston e,marl , shale , iron ore , clay , and fly ash .

The kiln resembles a large horizontal pipe with a diameter of 10 to 15 feet ( 3 to 4.1 meters ) and a length of 300 feet ( 90 meters ) or moe , One endi is raised slightly . THe raw mix is placed in the high end and as the kiln rotates the materials move slowly toward the lower end . Flame jets are at the lower end and all the materials in the kiln are heated to high temperatures that range between 2700 and 3000 Fahrenheit ( 1480 and 1650 Celcius ) . This high heat drives off , or calcines , the chemically combined water and carbon dioxide from the raw materials and forms new compounds ( tricalcium silicate , dicalcium silicate , tricalcium aluminate and tetracalcium aluminiferrite ) . For each ton od material that goes ionto the fedd end of the kiln , two thirds od a ton the mes out the discharge end , caled clinker . THis clinker is in the form of marble sized pellets . THe clinker is very finely ground to produce portlanc cement , A small amoount of gypsum is added during the drinding process to conrrol the cement set or rate od hardening .