Short answer: for most of a house, meaning foundations, brickwork, plaster and even RCC slabs, PPC is the better choice. It is a little cheaper, gives denser concrete over time, and handles damp soil better. Use OPC 53 grade where you need strength quickly: early de-shuttering, precast work, or cold-weather concreting. Always follow your structural engineer if they have specified a cement.
What the two cements are
OPC (Ordinary Portland Cement) is clinker ground with a little gypsum. In India it is sold in three grades under IS 269:2015: 33, 43 and 53. The number is the minimum strength in MPa at 28 days. You will mostly find 43 and 53 grade in shops.
PPC (Portland Pozzolana Cement) is OPC clinker blended with 15–35% fly ash, a by-product of thermal power plants (IS 1489 Part 1:2015). The fly ash reacts slowly with the lime released when cement sets. That reaction keeps adding strength and closing up pores for months after casting.
OPC vs PPC at a glance
| OPC 53 | PPC | |
|---|---|---|
| Standard | IS 269:2015 | IS 1489 (Part 1):2015 |
| Minimum 28-day strength (code) | 53 MPa | 33 MPa (most brands test well above this) |
| Early strength (3–7 days) | High | Lower |
| Long-term strength (90+ days) | Levels off | Keeps increasing |
| Heat while setting | High, so more risk of shrinkage cracks | Lower |
| Resistance to sulphates and salty, damp soil | Moderate | Better |
| Minimum moist curing (IS 456, clause 13.5.1) | 7 days | 10 days |
| Price | Usually a little higher | Usually a little lower |
The 33 MPa figure for PPC does not mean "weak". It is only the minimum the code requires. Check the brand's test certificate, which most dealers can give you.
Which cement for which part of the house
| Work | Better choice | Why |
|---|---|---|
| Footings and foundation concrete | PPC | Better resistance to moisture and salts in the soil |
| PCC below footings, plinth beam | PPC | No need for early strength |
| Brickwork mortar | PPC | Better workability, fewer cracks |
| Plaster (inside and outside) | PPC | Lower heat means fewer fine shrinkage cracks |
| Columns, beams, slab | Either, as per engineer | PPC is allowed by IS 456. Use OPC 53 if shuttering has to come off early. |
| Precast items, paver blocks, quick repairs | OPC 53 | Needs strength in days, not weeks |
| Concreting in cold weather (below about 10°C) | OPC | PPC gains strength very slowly in the cold |
Mistakes with PPC that cause weak concrete
- Adding extra water. Some masons add water because PPC concrete looks "stiff" at first. Every extra litre of water lowers the final strength. Keep the water-cement ratio your engineer gave you, usually around 0.45–0.50 for M20 slab concrete. If workability is a problem, ask for a plasticiser. Do not add water.
- Short curing. PPC needs at least 10 days of moist curing, and 14 in hot, dry weather. Stopping at 7 days, which is common on sites, cuts off the slow fly-ash reaction that gives PPC its strength.
- Removing slab props too early. PPC concrete is weaker than OPC concrete in the first week. Ask your engineer before de-shuttering. Do not just follow the OPC timeline.
- Mixing OPC and PPC in the same pour. Use one cement type and brand for a single slab or beam.
Check the bag before you buy
- Manufacturing week and year are printed on every bag. Cement loses strength as it ages. Avoid bags more than about 3 months old, and use older stock only for non-structural work.
- Lumps: press the bag. Hard lumps mean moisture has got in, so reject it.
- BIS mark and IS number (IS 269 for OPC, IS 1489 for PPC) should be clearly printed.
- Storage: stack bags on a wooden platform or plastic sheet, away from walls, no more than 10 bags high.
