How we supply it: PPC is arranged through a local partner dealer: the dealer quotes, supplies and bills the bags and pays us a referral commission. For plaster stages we can phase the cement in weekly drops alongside P-Sand loads, so you are not storing a month of bags through the rain.
In one line: PPC is a blended cement made by grinding OPC clinker and gypsum with 15–35% pozzolanic fly ash, as specified in IS 1489 (Part 1).
What the fly ash in PPC actually does
PPC is a blended cement made by grinding OPC clinker and gypsum with 15–35% pozzolanic fly ash, as specified in IS 1489 (Part 1). The fly ash reacts slowly with the lime that cement releases, turning it into extra binding gel.
That is why PPC concrete keeps gaining strength well past 28 days and becomes less porous. The price you pay is a slower start: IS 1489 asks for 33 MPa at 28 days on the standard mortar cube.
Cement types you will see at the dealer
| Bag label | Standard | Blended material | Typical use |
|---|---|---|---|
| OPC 53 | IS 269 | None (clinker and gypsum) | RCC frame, precast items |
| OPC 43 | IS 269 | None | General RCC and masonry |
| PPC | IS 1489 (Part 1) | 15–35% fly ash | Plaster, masonry, footings, general RCC |
| PSC | IS 455 | 25–70% slag | Footings and sumps in salty or coastal ground |
PPC or OPC: decide by the job, not the label
| Factor | PPC | OPC 53 |
|---|---|---|
| Strength at 3 to 7 days | Lower | Higher |
| Heat while setting | Lower | Higher |
| Density and permeability after months | Denser, less permeable | Good |
| Minimum moist curing (IS 456) | 10 days | 7 days |
| Feel in mortar | Smoother, more workable | Stiffer |
| Removing slab props early | Wait longer | Sooner |
Curing PPC: the 10-day rule
IS 456 asks for at least 10 days of moist curing when blended cements such as PPC are used, against 7 days for OPC. Stopping early throws away the very gain you chose PPC for.
In the April to June heat, fresh plaster dries out within hours. Spray it two or three times a day for the full period.
- Slabs: build small mortar bunds and pond water once the surface can take foot traffic
- Columns and beams: wrap wet hessian as soon as the shuttering comes off
- Plaster: start the morning after and keep going for the full 10 days
Bags for plaster and brickwork
Typical estimate: for 12 mm cement plaster: wet volume plus about a third for dry volume, joints and wastage. Rough brick walls take more.
- 1:4 plaster, 12 mm: about 0.86 bag and 0.19 MT of P-Sand per 100 sq ft
- 1:6 plaster, 12 mm: about 0.6 bag and 0.21 MT of P-Sand per 100 sq ft
- Brickwork in 1:6 mortar: about 1.5 to 1.6 bags per m³ of wall
Five checks on a PPC delivery
- The bag must say Portland Pozzolana Cement and IS 1489 (Part 1), with the ISI mark and licence number, not just 'fly ash cement'.
- Read the packing week and year; for plaster and RCC, prefer stock packed within the last two months.
- Squeeze each bag and reject any with hard lumps.
- Look at the stitching and the paper; torn bags pick up moisture on the way.
- Photograph one bag label per lot so any strength complaint can be traced to it.
Storing PPC on a plaster job
- PPC is as sensitive to damp as OPC; a wet floor lumps the bottom row within days.
- Leave a walkway round each stack so the lowest bags stay visible.
- For long plaster jobs take weekly drops instead of one big delivery.
- Keep bags away from the curing-water drum and from under leaking sheet roofs.
Where PPC jobs go wrong
- Curing PPC on an OPC timetable: three or four days of watering leaves the fly ash unreacted.
- Pulling slab props on the usual schedule in cool, wet weather.
- Reading 'slower' as 'weaker' and over-dosing cement in the mix.
- Buying 'fly ash cement' that has no IS 1489 marking.
- Plastering west walls in full afternoon sun without shade or follow-up spraying.