Types of Limes and their Properties

The limes are classified in three categories as fat lime, hydraulic lime and poor lime:

(1) Fat lime: It is composed of 95 percentage of calcium oxide. As water is added, it slakes vigorously and its volume increases 2 to 2^1/2 to times. It is in white color. Its properties are following :

1.    It has high degree of plasticity

2.    hardens slowly

3.    It is white in color

4.    It sets slowly in the presence of air

5.    It slakes vigorously.

(2) Hydraulic lime: It contains ferrous oxide and clay. Depending upon the percentage of clay exit, the hydraulic lime is divided into the following three categories:

   i.        Moderately hydraulic lime (11 to 20% clay content)

   ii.        Feebly hydraulic lime (5 to 10% clay content)

   iii.        Eminently hydraulic lime (21 to 30% clay content)

The properties of hydraulic lime are following:

Its color is not perfectly white

It is sets under water

Its binding property improves if fine powder is mixed with sand and kept in the form of heap for a week, before utilizing.

It forms a thin paste with water and do not dissolve in water.

(3) Poor lime: It contains more than 30% clay. Its color is muddy. It has poor binding property. The mortar composed with such type of lime is used for inferior works.

IS 712-1973 classifies lime as class A, B, C, D and E.

Class A Lime: It is predominantly hydraulic lime. It is usually supplied as hydrated lime and It is generally used for structural works.

Class B Lime: It contains hydraulic lime and fat lime both. It is supplied as hydrated lime or as quick lime. It is utilized for making mortar for masonry works.

Class C Lime: It is predominantly fat lime, supplied both as quick lime and fat lime. It is utilized for finishing coat in plastering and for white washing.

Class D Lime: This lime contains large quantity of magnesium oxide and is similar to fat lime. It is also commonly used for white washing and for finishing coat in plastering.

Class E Lime: It is not a pure lime stone. It is known as kankar. It is available in block and modular form. It is supplied as hydrated lime. It is usually used for masonry mortar.