OPC 53 and PPC compared
| OPC 53 | PPC (fly ash based) | |
|---|---|---|
| Indian Standard | IS 269:2015 | IS 1489 (Part 1):2015 |
| What is in it | Portland clinker and gypsum | Portland clinker, gypsum and 15–35% fly ash |
| Minimum strength at 3 days | 27 MPa | 16 MPa |
| Minimum strength at 7 days | 37 MPa | 22 MPa |
| Minimum strength at 28 days | 53 MPa | 33 MPa |
| Heat while setting | Higher | Lower |
| Strength gain | Fast early strength | Slower early; keeps gaining after 28 days |
| Minimum moist curing (IS 456) | 7 days | 10 days |
| Shrinkage cracks in plaster | More likely if curing is poor | Less likely |
| Typical jobs | Precast items, early de-shuttering, mix designs that call for it | Masonry, plaster, PCC, footings, slabs with proper curing |
Verdict: PPC for plaster, brick and block mortar, PCC and most house concrete, provided the concrete is kept wet for at least 10 days. OPC 53 when you need strength in days rather than weeks, or when your engineer's mix design names it.
Which cement for which job
| Job | Cement | Note |
|---|---|---|
| Wall and ceiling plaster | PPC | Lower heat, fewer shrinkage cracks |
| Brick and block mortar | PPC | Workable; slower setting suits masonry |
| PCC bed, footings | PPC | Keep wet for at least 10 days |
| Roof slab, beams, columns | PPC or OPC 53 | Follow the mix design; cure PPC for 10 days |
| Precast lintels, paver and block making | OPC 53 | Moulds can be reused sooner |
| Ready-mix concrete | As per the plant's mix design | The plant chooses; check the delivery ticket |
From our team
Notes, photos and examples added by the M&B Chetty team, with the author and the date.
Buying and storing cement
- Bag: 50 kg. Check the week and year of manufacture printed on the bag and use older stock first.
- Storage: keep bags on a raised platform or pallets, off the floor and away from walls, covered against rain, stacked no more than about 10 high.
- Lumps: lumps that do not crumble between your fingers mean the cement has taken moisture; keep it out of structural work.
- Grade: buy what your engineer specified; grades are not interchangeable in a mix design.
How we arrange cement
Cement is a partner item for us. We arrange it, along with paints, putty, electricals, windows, doors, wood work, plumbing and tiles, through local partner suppliers, who pay us a referral commission. Our OPC 53 and PPC rate pages show an indicative Chennai market rate per bag; the partner supplier confirms the brand and the day's rate when you order.
What we supply ourselves is the rest of the mix: washed M-Sand, P-Sand and jalli from the Perindesam works, and river sand, TMT bars, blocks and bricks from our stock yards.