OPC or Ordinary Portland Cement, is most commonly used cement. OPC is the basic form of cement produced by inter-grinding cement clinker with 3-5% gypsum – which is introduced to enhance the setting time of the cement to a workable 30 minutes or so.
Bureau of Indian Standards (BIS) has classified OPC into 3 different grades namely, OPC 33 Grade, OPC 43 Grade and OPC 53 Grade cements. The grade number indicates the minimum compressive strength that the cement is required to attain at the end of 28 days