---
title: "Why pozzolana is used in PPC"
subject: "Civil Engineering Materials"
chapter: 5
key: "semester_3/civil_engineering_materials:why-pozzolana-in-ppc"
source: https://www.bctengineer.com/q/semester_3/civil_engineering_materials/why-pozzolana-in-ppc
site: BCT Engineering
---

# Why pozzolana is used in PPC

Civil Engineering Materials · Chapter 5: Cement

- Asked in: 2081 Chaitra (new course), 1 marks
- Video: [Why Pozzolana portland Cement PPC is more popular | PPC Vs OPC | Benefit of PPC Cement](https://www.youtube.com/watch?v=wmtoRQELVCs) — CementPDM by CemNex
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_3/civil_engineering_materials/why-pozzolana-in-ppc
- Whole chapter: https://www.bctengineer.com/md/semester_3/civil_engineering_materials/chapter-5

## Question

Why is pozzolana used to make PPC (Portland Pozzolana Cement)?

## Short answer

Pozzolana reacts with calcium hydroxide from cement hydration to form extra C-S-H gel, enhancing durability, sulphate resistance, and reducing heat of hydration. It also lowers permeability and cost while utilizing industrial waste.

## Answer

Pozzolana (such as fly ash or calcined clay) is a siliceous material that, with moisture, reacts with the calcium hydroxide released by hydrating cement to form extra C-S-H gel. It is used in PPC to:

- improve durability and resistance to sulphates, chlorides and chemicals;
- reduce heat of hydration and cracking in mass concrete;
- give a denser, less permeable concrete and lower efflorescence;
- reduce cost and save clinker and energy (reducing CO2), and use industrial waste.

## Check yourself

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

1. Pozzolana reacts with:
   A. Gypsum to form lime
   B. Sand
   C. Steel
   D. Calcium hydroxide to form extra C-S-H gel
   Answer: D. A siliceous material reacting with moisture and lime. (Key point: Reaction)

2. Pozzolana in PPC helps by:
   A. Reducing heat of hydration
   B. Raising heat
   C. Making set instant
   D. Reducing durability
   Answer: A. It reduces cracking in mass concrete. (Key point: Heat)

3. Another reason for using it:
   A. Costs more
   B. Saves clinker, energy and uses industrial waste
   C. Adds CO2
   D. Lowers sulphate resistance
   Answer: B. Also denser, less permeable concrete. (Key point: Economy)

## Related in Civil Engineering Materials

- [Ingredients of cement and functions](https://www.bctengineer.com/question.md?key=semester_3%2Fcivil_engineering_materials%3Aingredients-of-cement-functions) — Civil Engineering Materials, chapter 5, asked 7×
- [Cement and mud mortar properties, uses](https://www.bctengineer.com/question.md?key=semester_3%2Fcivil_engineering_materials%3Acement-mud-mortar-properties-uses) — Civil Engineering Materials, chapter 6

## Related in other subjects

- [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
- [OPC versus PPC](https://www.bctengineer.com/question.md?key=semester_5%2Fconcrete_technology_and_masonry_structure%3Aopc-vs-ppc) — Concrete Technology and Masonry Structure, chapter 1
- [Damper winding to make motor self starting](https://www.bctengineer.com/question.md?key=semester_5%2Felectric_machines_ii%3Adamper-winding-self-starting) — Electric Machines II, chapter 2
- [Mortar properties; cement and sand for 10 cum](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Amortar-quantity-10cum) — Building Technology, chapter 3