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 2x(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 predominently 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 predominently 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 similar to fat lime.
This is also commonly used for white washing and for finishing coat in plastering.
Class E Lime: It is an impure lime stone, known as kankar. It is available in modular and block form. It is supplied as hydrated lime. It is commonly used for masonry mortar.