What is the difference between mortar and plaster and which is best for your house?

The term mortars are used to indicate a paste prepared by adding the required quantity of water to a mixture of binding material like cement or lime and fine aggregate like sand. There are different

types of mortars.

Types of mortars:-

1. Bulk density
2. Kind of binding material
3. Nature of application
4. Special mortars

• Bulk density:- According to the bulk density there are two types of mortar:-

1. Heavy mortars:- The mortars having a bulk density of 15 Kn/m3 or more are known as heavy mortars and they are prepared from heavy quartz or other sands.
2. Lightweight Mortars:- The mortars having a bulk density less than 15kN/m3 are known as lightweight mortars and they are prepared from light porous sands from pumice and other fine aggregates.

• Kind of binding material: The kind of binding material for a mortar is selected by keeping in mind several factors such as expected working conditions, hardening temperature, moisture conditions, etc. According to this kind of binding material, the mortars are classified into the following five categories:

• Lime mortar
• Surkhi mortar
• Cement mortar
• Gauged mortar
• Gypsum mortar

1. Lime mortar: In this type of mortar, lime is used as binding material. The lime may be fat lime or hydraulic lime. The fat lime shrinks to a great extent and hence it required about 2 to 3 times its volume of sand. The lime should be slaked before use. This mortar is unsuitable for water-logged areas or in damp situations.

• Surkhi mortar: This type of mortar is prepared by using fully surkhi instead of sand or by replacing half of sand in the case of fat lime mortar. The powder of surkhi should be fine enough to pass BIS no. 9 sieves and the residue should not be more than 10% by weight. The surkhi mortar is used for ordinary masonry work.

• Cement mortar: In this type of mortar, cement is used as binding material. Depending upon the strength required and importance of work, the proportion of cement to sand by volume varies from 1:2 to 1:6 or more. It should be noted that surkhi and cinder are not chemically inert substances and hence they cannot be used as adulterants with the matrix as cement. Thus the sand only can be used to form cement mortar.

• Gauged mortar: To improve the quality of the lime mortar and to achieve early strength, cement is sometimes added to it. This process is known as gauging. It makes a lime mortar economical, strong, and dense. The usual proportion of cement to lime by volume is about 1:6 to 1:8. It is also known as the composite mortar or lime-cement mortar and it can also be formed by the combination of cement and clay. This mortar may be used for bedding and for thick brick walls.

• Gypsum mortar: These mortars are prepared from gypsum binding materials such as building gypsum and anhydrite binding materials

• Nature of application:- According to this, there are two types of mortar:-

1. Bricklaying mortars:- The mortars for bricklaying are intended to be used for brickwork and walls. Depending upon the working conditions and type of construction, the composition of masonry mortars concerning the kind of binding material is decided.
2. Finishing mortars:- These mortars include common plastering work and mortars for developing architectural or ornamental effects. Cement or lime is generally used as binding material for ordinary plastering mortar.

• Special mortars:-

1. Fire-resistant mortar
2. Lightweight mortar
3. packing mortar
4. sound-absorbing mortar
5. X-ray shielding mortar.