CEMENT HAS BEEN CLASSIFIED ON THE BASIS OF IT'S STRENGTH, GRADE , COLOUR AND USE FOR SPECIFIC PURPOSES

CEMENT :-- It is a material that has cohesive and adhesive properties in the presence of water and is called hydraulic cement and it consists primarily silicates and aluminates of lime obtained from lime stone and clay .This mixture is ground blended fuses in a kiln at about 1400 degree C and a product clinker is obtained it is cooled and ground to get cement and is called Portland cement. The bureau of Indian standard describe following types of the cement  OPC -33 grade specifications and PPC , Rapid hardening Portland cement, Portland slag , High strength OPC 43 grade and 53 grade OPC , Hydrophobic cement, High Alumina cement ,super sulphates cement, masonry cement,oil well cement , ,white Portland cement besides this there are few more specific cement such as,coloured cement, water proof cement, expanding cement, ,sand cement and air entertaining Portland cement. OPC  is the basic portal cement and declared best for general concrete construction. It is produced by grinding Portland clinker with the possible addition of small quantity of gypsum ,water or both and not more than 1 percent of air entraining agents .It consist 59 to 64 percent lime and 19 to 24 percent silica with 3to 6 percent alumina and 1to 4 percent iron oxide .The BIS has graded OPC in three grades , namely,33 ,43 and 53 grade on the basis of 28! days compressive strength of cement and separate specifications have been brought out for each grade of cement to deal with their physical properties.In addition the BIS has further classified the cement into six categories on the basis of 28 days compressive strength as follows  :-- (1) 325 to 375 kg per square centimetre (2) 375 to 425 (3) 425 to 475  (4) 475 to  525 (5) 525 to 575 and (6) 575 to 625 or 62.5 MPa.