---
title: "OPC versus PPC"
subject: "Concrete Technology and Masonry Structure"
chapter: 1
key: "semester_5/concrete_technology_and_masonry_structure:opc-vs-ppc"
source: https://www.bctengineer.com/q/semester_5/concrete_technology_and_masonry_structure/opc-vs-ppc
site: BCT Engineering
---

# OPC versus PPC

Concrete Technology and Masonry Structure · Chapter 1: Introduction to concrete and concrete materials

- Asked in: 2064 Jestha (old course)
- Video: [Difference between OPC & PPC || Civil Bytes](https://www.youtube.com/watch?v=oZHLhdp-mo8) — Civil Bytes
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_5/concrete_technology_and_masonry_structure/opc-vs-ppc
- Whole chapter: https://www.bctengineer.com/md/semester_5/concrete_technology_and_masonry_structure/chapter-1

## Question

Differentiate Ordinary Portland Cement (OPC) and Portland Pozzolana Cement (PPC) in terms of their physical and chemical properties.

## Short answer

O PC is clinker with gypsum, P PC contains 15-35% pozzolana like fly ash, making it finer, lower early strength, lower heat, better chemical resistance, denser pore structure, but requires longer curing. O PC gains strength faster and is used for precast work.

## Answer

**OPC** is made by grinding clinker with gypsum (IS 269). **PPC** is made by inter-grinding (or blending) OPC clinker and gypsum with 15-35% fly ash or other pozzolana (IS 1489 Part 1).

| Point | OPC | PPC |
|---|---|---|
| Composition | Clinker + 3-5% gypsum | Clinker + gypsum + 15-35% pozzolana (fly ash/calcined clay) |
| Fineness (Blaine) | Not less than 225 m$^2$/kg | Not less than 300 m$^2$/kg (finer) |
| Initial setting time | Not less than 30 min | Not less than 30 min |
| Final setting time | Not more than 600 min | Not more than 600 min |
| Early strength | Higher (3 and 7 day) | Lower early strength |
| 28-day strength (min.) | 33/43/53 MPa | 33 MPa; continues to gain strength later |
| Heat of hydration | Higher | Lower (suitable for mass concrete) |
| Free lime / Ca(OH)$_2$ | More | Less, as the pozzolana consumes it |
| Workability and cohesion | Normal | Better, due to the fine spherical fly ash particles |
| Permeability | Higher | Lower; denser pore structure |
| Sulphate and chemical resistance | Poor to fair | Better |
| Curing | Normal (7 days) | Needs longer curing (10 days) |
| Colour | Grey | A slightly different shade of grey, depending on the pozzolana |
| Chemical limits | MgO max 6%; loss on ignition max 5% | MgO max 6%; loss on ignition max 5% |
| Cost | Higher | Cheaper and environmentally friendly |

PPC is preferred for plastering, mass concrete and marine works; OPC is used where fast strength gain is required (precast work, early formwork removal).

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. PPC contains:
   A. None
   B. 15-35% pozzolana
   C. 60% pozzolana
   D. Only gypsum
   Answer: B. Fly ash or calcined clay is inter-ground. (Key point: Composition)

2. PPC compared with OPC has:
   A. Higher heat
   B. Higher early strength
   C. Lower heat and lower early strength
   D. Coarser grains
   Answer: C. Suitable for mass concrete. (Key point: Heat)

3. PPC needs:
   A. Shorter curing
   B. No curing
   C. 3 days
   D. Longer curing (about 10 days)
   Answer: D. Pozzolanic reaction is slower. (Key point: Curing)

## Related in Concrete Technology and Masonry Structure

- [Microstructure of ordinary Portland cement](https://www.bctengineer.com/question.md?key=semester_5%2Fconcrete_technology_and_masonry_structure%3Amicrostructure-opc) — Concrete Technology and Masonry Structure, chapter 2
- [Physical properties of OPC and concrete behaviour](https://www.bctengineer.com/question.md?key=semester_5%2Fconcrete_technology_and_masonry_structure%3Acement-physical-properties) — Concrete Technology and Masonry Structure, chapter 1
- [Physical and chemical causes of deterioration](https://www.bctengineer.com/question.md?key=semester_5%2Fconcrete_technology_and_masonry_structure%3Aphysical-chemical-causes-deterioration) — Concrete Technology and Masonry Structure, chapter 6, asked 5×

## Related in other subjects

- [Why pozzolana is used in PPC](https://www.bctengineer.com/question.md?key=semester_3%2Fcivil_engineering_materials%3Awhy-pozzolana-in-ppc) — Civil Engineering Materials, chapter 5
- [Chemical versus physical weathering; factors](https://www.bctengineer.com/question.md?key=semester_3%2Fengineering_geology_i%3Achemical-versus-physical-weathering-factors) — Engineering Geology I, chapter 6
- [Physical and chemical weathering](https://www.bctengineer.com/question.md?key=semester_3%2Fengineering_geology_i%3Aphysical-and-chemical-weathering) — Engineering Geology I, chapter 6, asked 5×
- [Physical and chemical disintegration](https://www.bctengineer.com/question.md?key=semester_4%2Fsoil_mechanics%3Aphysical-chemical-disintegration) — Soil Mechanics, chapter 1