Lime is an ancient engineering material used as a cementing material. The Egyptians and Romans made remarkable application of this material for various constructional purposes. Even in India, lime has been a popular engineering material which was used as a binding material in various structures such as palaces, forts, monuments etc., some of them still exist in perfectly good condition.
Now a days, cement has become most popular binding material compared to lime, but lime is still used where locally available.
Lime is usually not found in natural/free state. It is obtained by burning one of the following materials :
- Lime stones from stone hills
- Boulder of limestones from the beds of old river
- Kankar found below the ground
- Shells of sea animals
Classification of Lime :
- Fat Lime
It is also known as high calcium lime, pure lime, rich lime or white lime, but popularly known as Fat lime, as it slakes vigorously and its volume is increased to about 2 to 2.5 times the volume that of quicklime.
It is obtained by calcining pure carbonate of lime which is composed of about 95% of calcium oxide. The percentage impurities in such limestone is < 5%.
Properties of Fat Lime :
- Hardens very slowly
- High degree of plasticity
- Colour is pure white
- Sets slowly in presence of air
- Slakes vigorously
Uses of Fat Lime :
- Whitewashing and plastering of walls
- When mixed with sand can be used for thin joints of brickwork and stone arts.
2. Hydraulic Lime
It is also known as water lime as it sets under water. It consist of clay and some amount of ferrous oxide.
| Item | Feebly Hydraulic Lime | Moderatly Hydraulic Lime | Eminently Hydraulic Lime |
| Clay content | 5-10% | 11-20% | 21-30% |
| Slaking Action | Slakes after few minutes | Slakes after 1 or 2 Hrs | Slakes with difficulty |
| Setting Action | Sets in water in 3 weeks or so | Sets in water in 1 or 2 weeks | Sets in water in a day |
| Uses | For ordinary masonry work | For superior type of masonry work | For damp places |
Properties of Hydraulic Lime :
- It can set under water and in thick walls where there is no free circulation of air.
- Colour not perfectly white
- Forms thin paste with water i.e. does not dissolve in water
Uses of Hydraulic Lime :
- Used for plaster work.
3. Poor Lime
It is also known as impure lime or lean lime. It consists of clay > 30%.
Properties of Poor Lime :
- Slakes very slowly
- Forms a thin paste with water
- Sets or hardens very slowly
- Muddy white colour
Uses of Poor Lime :
- Used for interior type of work or at places where good lime is not available.
