Clay lumps are collected
and are wetted with water and allowed to mature for 1 or 2 days. It is kneeded well until it attains required consistancy. Sometimes fibrous materials like gobber is added in the mix.
It prevents cracks
in the plaster. If plaster is to be used for outer walls, it is sprayed or
painted with Bitumen. It is cheap mortar. Its durability is less. It is normally
used for the construction of temporary sheds and cheap houses in rural areas.
The following are
some of the special mortars:
1. Cement clay mortar
2. Gauged mortar
3. Decorative mortar.
1. Cement Clay
Mortar:
Quality of clay
mortar can be improved by adding cement to the mix. Normal proportion of clay
to cement is 1:1. It maintains the economy to some extent and there is sufficient
improvements in the durability of mud-mortar.
2. Gauged Mortar:
It is the mortar
obtained by adding cement to lime mortar. The usual
proportion of cement, lime and sand
are 1:1:6, 1:2:9 and 1:3:12. This mortar is to be used within half an hour after
mixing cement. Obviously, it is cheaper than cement mortar and its quality is
between that of cement mortar and lime mortar.
3. Decorative
Mortar:
These mortars are
obtained by using coloured cement. They are used to
give pleasant appearance to
outer walls.