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.