WHAT IS MORTAR - PROPERTIES, TYPES AND USES

What is Mortar

Mortar is a paste made by cement and water or by lime, surkhi and water. Lime and cement is a binding material in the mortar.Sand and surkhi give the strength to the mortar.It is a material used in masonry construction to fill the gaps between the bricks and blocks used in construction.

Properties of Good Mortar 

• It should be durable.
• It should be cheap.
• It should be easily workable.
• It should possess high durability.
• It should set quickly so that speed in construction may be achived.
• It should be capable of developing good adhesion with the building units such as bricks,stone etc. 
• The joints formed  by mortar should not develop cracks and should be able to maintain their appearance for a sufficiently long period.

Types of Mortar Used In Masonry Construction

1. Based on Applications
2. Based on Binding Materials
3. Based on Strength 
4. Based on Bulk Density
5. Based on Special Purpose of Mortars

Based on Application

1. Brick Laying Mortar

This type of mortar used to bind bricks in masonry construction.The ratio of the ingredients of brick laying mortar is decided based on kind of binding material used. 

2. Finishing Mortar

Finishing mortar is used for pointing and plastering works.It should have great strength,mobility and resistance against atmospheric action.This mortar is also used for ornamental finishing.

Based on Building Materials

1. Cement Mortar

Cement mortar is a homogenous paste of cement, sand and water.Different cement mortars are obtained by mixing different proportion of cement and sand.Cement mortar will give strength and resistance against water.The ratio of cement mortar is varies to 1:2 to 1:6.

2. Lime Mortar

Lime is used as a binding material, lime mortar is composed of lime and an aggregate such as sand, mixed with water.There are two types of lime fat lime and hydraulic lime.Lime mortar are flexible, allowing for movement in the building and thus preventing cracks in the masonry.

3. Gypsum Mortar

Gypsum mortar is made up from gypsum, which requires a lower firing temperature.Gypsum mortar is not durable as other mortars in damp conditions.

4. Surkhi Mortar

Surkhi is made by grinding brunt brick,brick-bats or burnt clay. Surkhi mortar is a mixture of lime, surkhi and water. Surkhi is finely-powdered brunt clay which provides more strength than sand and it is cheaply available in the market.

5. Mud Mortar

Mud mortar is a type of mortar where mud is used as binding materials.In mud mortar rice-husk, cow dung and sawdust is used as fine aggregate.Mud mortar is used where lime or cement is not available.

6. Gauged Mortar

Gauged mortar is a type of mortar where cement and lime both are used as binding materials and sand is used as fine aggregate. In gauged mortar cement is added to enhance the strength of the mortar.It economical than cement mortar.The cement to the lime propertion varies from 1:6 to 1:9.

Based on Bulk Density

1. Light Weight Mortar

When the mortar having bulk density less than 15 KN/m3 then it is called as light mortar.It is prepared by mixing rice-husk, jute fibers, saw dust, coirs or asbestos fibers along with sand and lime or cement as binder.It is generally used in the soundproof and heat proof constructions.

2. Heavy Weight Mortar

When the mortar having bulk density of 15KN/m3 or more then it is called as heavy mortar.

Based on Strength

1. Type M Mortar

Type M mortar is considered to be the strongest mortar.It is the highest strength mortar minimum 17.2 Mpa.It is used for exterior masonry work.This type of mortar is used where lateral load or substantial gravity are exerted.Load bearing wall retaining wall, footings etc its example.

2. Type S Mortar

Type S mortar is considered to be the medium strength mortar minimum 12.4 MPa with high bonding ability.It is used for grade application with normal to moderate loading. Type S mortar has great durability that is why it is highly suitable for locations where the masonry is in contact with the ground, such as shallow retaining wall.

3. Type N Mortar

It is medium strength mortar with 5.2 MPa and most common type of mortar.Type N mortar used for reinforced interior and above grade exterior load-bearing walls on which normal loads are imposed.

4. Type O Mortar

Type O mortar is considered to be a low strength mortar with minimum 2.5 MPa. Type O mortar is used for interior non load bearing applications with very limited exterior use.

Based On Special Purpose of Mortars

1. Fire Resistant Mortar

Fire resistant mortar is prepared by mixing aluminous cement to the fine powder of fire bricks.If there are any fire warnings to the structures in a particular zone, then fire resistant mortar will be used which acts as fireproof shield.

2. Packing Mortar

The constituents of packing mortars are generally cement-sand, cement-loam or sometimes cement-sand-loam.This type of mortar is used to pack the oil wells. Packing mortar should be of high homogeneity, water resistance and high strength.

3. Sound Absorbing Mortar

In sound absorbing mortar cement, lime, gypsum or slag is used as a binding materials while pumice and cinder as fine aggregate.It is used to reduce the level of noice and acts as sound proof layer.

4. X-ray Shielding Mortar

X-ray shielding mortar is used in the x-ray room.To provide protection against x-rays the room walls and ceilings are plastered with  X-ray shielding mortar.This mortar is of heavy type with bulk density around 22KN/m3.Fine aggregates from heavy rock and suitable admixture are used to prepare this type of mortar.

5. Chemical Resistant Mortar

Chemical resistant mortar is made of by the combination of liquid and powder, it should be mixed in proportion from workable mortar which after setting and curing of liquid get solid.

The additives added may not resist all the chemical attacks.For example silicate type chemical mortar resists nitric, chromic, sulphuric or any acidic damage but it cannot prevent the structure against damage by alkalies of any concentration.

Uses of Mortar in Masonry Construction

• It is used to bind the bricks and stones with each other.
• It is used for plastering.
• It is used to hide the openjoints of brickwork and stonework.
• It is used to repair cracks in structure.
• It is used to distribute uniform load over the lower brick.
• It is use to improve the general appearance of the structure.