Solution:

Types of Limes and their Properties:

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

(i) Fat lime:

It is composed of 95 percentage of calcium oxide. When water is added, it slakes vigorously and its volume increases to 2 to 2 1 2 times. It is white in colour.

Its properties are:

(a) hardens slowly

(b) has high degree of plasticity

(c) sets slowly in the presence of air

(d) white in colour

(e) slakes vigorously

(ii) Hydraulic lime:

It contains clay and ferrous oxide. Depending upon the percentage of clay present, the hydraulic lime is divided into the following three types:

(a) Feebly hydraulic lime (5 to 10% clay content)

(b) Moderately hydraulic lime (11 to 20% clay content)

(c) Eminently hydraulic lime (21 to 30% clay content)

The properties of hydraulic limes are:

• Sets under water

• Colour is not perfectly white

• Forms a thin paste with water and do not dissolve in water.

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

(iii) Poor lime:

It contains more than 30% clay. Its colour is muddy. It has poor binding property. The mortar made with such 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 normally supplied as hydrated lime and is commonly used for structural works.

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

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

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

Class E Lime: It is an impure limestone, known as kantar. It is available in modular and block form. It is supplied as hydrated lime. It is commonly used for masonry mortar.