---
title: "Hydrated versus hydraulic lime"
subject: "Civil Engineering Materials"
chapter: 4
key: "semester_3/civil_engineering_materials:hydrated-hydraulic-lime-difference"
source: https://www.bctengineer.com/q/semester_3/civil_engineering_materials/hydrated-hydraulic-lime-difference
site: BCT Engineering
---

# Hydrated versus hydraulic lime

Civil Engineering Materials · Chapter 4: Lime

- Asked in: 2065 Shrawan (old course), 4 marks
- Video: [Classification of Lime(Fat Lime,Hyrdaulic Lime,Poor Lime)//with main Points..](https://www.youtube.com/watch?v=_Mp6CqSnQrE) — Glowup Education
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_3/civil_engineering_materials/hydrated-hydraulic-lime-difference
- Whole chapter: https://www.bctengineer.com/md/semester_3/civil_engineering_materials/chapter-4

## Question

Differentiate between hydrated and hydraulic lime.

## Short answer

Hydrated lime is dry Ca(OH)₂ powder from quicklime plus limited water, non-hydraulic and sets only in air. Hydraulic lime is from clayey limestone, contains calcium silicates/aluminates, sets underwater and has higher strength.

## Answer

| Basis | Hydrated lime | Hydraulic lime |
|---|---|---|
| Meaning | Quicklime treated with a limited amount of water (Ca(OH)₂ dry powder) | Lime made from limestone containing clay |
| Source | Any quicklime, usually fat lime | Clayey limestone (5-30% clay) |
| Composition | Calcium hydroxide | Calcium silicates, aluminates and CaO |
| Hydraulicity | Non-hydraulic, sets in air only | Sets under water |
| Form | Fine dry powder, easy to store and transport | Lumps or powder |
| Strength | Low | Higher |
| Use | Plaster, whitewash and as an additive | Masonry in damp places |

## Check yourself

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

1. Hydrated lime is:
   A. Calcium hydroxide dry powder
   B. Calcium carbonate
   C. Calcium silicate
   D. Gypsum
   Answer: A. Quicklime with limited water. (Key point: Hydrated lime)

2. Hydrated lime is:
   A. Hydraulic
   B. Non-hydraulic, sets in air only
   C. Sets under water
   D. Underwater
   Answer: B. Hydraulic lime sets under water. (Key point: Hydraulicity)

3. Hydrated lime is a:
   A. Lump
   B. Paste
   C. Fine dry powder easy to store
   D. Liquid
   Answer: C. Hydraulic can be lumps or powder. (Key point: Form)

4. Hydraulic lime comes from:
   A. Pure limestone
   B. Gypsum
   C. Sand
   D. Limestone with 5-30% clay
   Answer: D. Hydrated from quicklime. (Key point: Source)

## Related in Civil Engineering Materials

- [Fat lime versus hydraulic lime](https://www.bctengineer.com/question.md?key=semester_3%2Fcivil_engineering_materials%3Afat-hydraulic-lime-difference) — Civil Engineering Materials, chapter 4, asked 3×
- [Quick lime versus hydraulic lime](https://www.bctengineer.com/question.md?key=semester_3%2Fcivil_engineering_materials%3Aquick-lime-hydraulic-lime-difference) — Civil Engineering Materials, chapter 4
- [Hydraulic and fat lime properties](https://www.bctengineer.com/question.md?key=semester_3%2Fcivil_engineering_materials%3Ahydraulic-fat-lime-properties) — Civil Engineering Materials, chapter 4
- [Short note: hydraulic lime](https://www.bctengineer.com/question.md?key=semester_3%2Fcivil_engineering_materials%3Ahydraulic-lime-short-note) — Civil Engineering Materials, chapter 4
- [Types of hydraulic lime](https://www.bctengineer.com/question.md?key=semester_3%2Fcivil_engineering_materials%3Atypes-hydraulic-lime) — Civil Engineering Materials, chapter 4
- [Cement mortar versus lime mortar](https://www.bctengineer.com/question.md?key=semester_3%2Fcivil_engineering_materials%3Acement-vs-lime-mortar) — Civil Engineering Materials, chapter 6

## Related in other subjects

- [Permeability versus hydraulic conductivity](https://www.bctengineer.com/question.md?key=semester_3%2Fengineering_geology_i%3Apermeability-versus-hydraulic-conductivity) — Engineering Geology I, chapter 6