Gypsum stands for an additive and it’s objective is to enhance the setting time of the cement to a executable 30 minutes or more.
OPC Cement provides high compressive strength at initial phases and at 28 days. A 53 Grade cement provides equal to 70 MPa strength across a minimum 53 MPa stated by BIS. Therefore, fly ash can also be blended (minimum 20% by weight of cement) in concrete as part replacement of cement at jobsite.
Due to this the material cost of concrete is saved significantly as well as durable properties can be maintained because of pore refinement (Less porous concrete).
If the concrete is formed in this way, the adaptability of concrete is enhanced greatly and it leads to higher strength in due course.
Recommended use for OPC 53 Grade Cement:
OPC 53 Grade cement is normally mostly suitable for Structural Concrete or Reinforced Concrete Works (like Columns, Beams, Slab etc.,).
PPC (Fly Ash Based) Cement:
Alternatively, PPC (Portland Pozzolana Cement) is formed with 75 – 77% cement clinker, 20% flyash and 3-5% gypsum.
Recommended use for PPC: Flyash based cement (PPC) will be effective for brick masonry, plastering, tiling and waterproofing works. In these works, strength is not a vital factor. PPC is more beneficial as compared to OPC because PPC contains slower rate of heat of hydration.
Thus PPC is likely to less cracks & shrinkage), superior workability and finishing (because fly ash based cement are circular in shape and thinner in size).