Types of Lime

TYPES OF LIME

When lime is heated, CO₂ is emitted and is reabsorbed when the lime materials slowly dry, set and harden. The re-absorption of CO₂ completes the lime cycle and makes using lime environmentally friendly and sustainable. Following are the different types of lime:

Quick lime:

Quick lime is obtained by calcination (i.e. heating to redness) of comparatively pure lime stone. It is the cheapest form of lime and is also known as caustic lime. It is amorphous in nature, highly caustic and possesses great affinity to moisture. It is ty to moisture. It is the main ingredient in the manufacturing of cement.

Slacked lime:

Slacked lime is also known as hydrated lime. It is obtained by slaking process, which is the chemical combination of quick lime with water. It has got the tendency of absorbing carbonic acid from the atmosphere in presence of water. It is ordinary pure lime, in white powder form, available in market.

Fat lime:

Fat lime is also known as high calcium lime or pure lime. Sometimes it is called as rich lime or white lime as it is white in colour. It is popularly known as fat lime as it slakes vigorously and its volume is increased to about 2 to 2.5 times that of quick lime. It is composed of 95 percentage of calcium oxide. It hardens slowly and has high degree of plasticity. This lime is used for various purposes as white washing, plastering of walls, as lime mortar with sand for pointing in masonry work, as a lime mortar with surkhi for thick masonry walls, foundations, etc.

Hydraulic lime:

Hydraulic lime is also known as water lime since its sets under water. This lime contains some amount of ferrous oxide with clay. Its Colour is not perfectly white and forms a thin paste with water and do not dissolve in water. The binding property can be improved by mixing its fine powder with sand and kept idle for a week before using. Depending upon the percentage of clay content, IS has divided hydraulic lime in three classes namely:

❖ Class A - Eminently hydraulic (21 to 30% clay content)

❖ Class B - Semi Hydraulic (11 to 20% clay content)

❖ Class C-Non-hydraulic (Feebly hydraulic lime) (5 to 10% clay content)

Poor lime:

Poor lime contains more than 30% of impurities, in the form of silica, Alumina and iron oxide. The mortar from this lime is of poor quality, since it contains more than 30% clay. Its colour is muddy and has poor binding property. The mortar made with such lime is used for substandard works.