---
title: "Determining slaking nature of lime"
subject: "Civil Engineering Materials"
chapter: 4
key: "semester_3/civil_engineering_materials:slaking-nature-of-lime"
source: https://www.bctengineer.com/q/semester_3/civil_engineering_materials/slaking-nature-of-lime
site: BCT Engineering
---

# Determining slaking nature of lime

Civil Engineering Materials · Chapter 4: Lime

- Asked in: 2068 Chaitra, 2 marks
- Video: [slaking of lime 001](https://www.youtube.com/watch?v=XT3qaar9yi8) — Gav Abe
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_3/civil_engineering_materials/slaking-nature-of-lime
- Whole chapter: https://www.bctengineer.com/md/semester_3/civil_engineering_materials/chapter-4

## Question

How will you determine the slaking nature of lime?

## Short answer

Add water to a quicklime lump: fat lime slakes violently with much heat and volume expansion, making a fine paste; hydraulic lime slakes slowly with little heat and leaves gritty residue; poor lime barely slakes.

## Answer

The slaking nature is a field test of the lime class.

1. Take a small lump of quicklime in a container and add water.
2. Observe the reaction.
   - **Fat lime:** slakes quickly and violently, producing great heat and steam, swelling to 2 to 2.5 times its volume and forming a fine white paste.
   - **Hydraulic lime:** slakes slowly with little heat and little swelling and leaves a gritty residue.
   - **Poor lime:** hardly slakes and gives little heat.

The time taken and the heat evolved, together with the volume expansion, show the nature of the lime. A thermometer can record the maximum temperature rise.

## Check yourself

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

1. Fat lime on adding water:
   A. Slakes slowly
   B. Does not slake
   C. Slakes quickly with great heat and steam
   D. Becomes gritty
   Answer: C. Swells 2-2.5 times. (Key point: Fat lime)

2. Hydraulic lime leaves:
   A. Fine paste
   B. No residue
   C. Powder
   D. Gritty residue
   Answer: D. Slow with little heat. (Key point: Hydraulic)

3. Poor lime:
   A. Hardly slakes with little heat
   B. Violent
   C. Boils
   D. Burns
   Answer: A. Over 30% clay. (Key point: Poor lime)

## Related in Civil Engineering Materials

- [Calcination and slaking of lime](https://www.bctengineer.com/question.md?key=semester_3%2Fcivil_engineering_materials%3Acalcination-slaking-lime) — Civil Engineering Materials, chapter 4, asked 3×

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