Understanding Mortars: Types, Bulk Density, and Applications
Mortars are essential in construction, and they can be classified based on several factors: bulk density, type of binding material, nature of applications, and special properties/mortar. Here’s a comprehensive look at these classifications.
Classification of Mortars Based on the,
1. Bulk Density
- Heavy Mortars: Mortars with a bulk density of 15 kN/m³ or more. They are made from heavy quartz or other dense sands.
- Lightweight Mortars: Mortars with a bulk density of less than 15 kN/m³. These are prepared from light, porous sands, pumice, and other fine aggregates.
2. Types of Binding Material
The choice of binding material is crucial and depends on factors like working conditions and moisture levels. Mortars are classified into the following categories based on binding materials:
1. Lime Mortar:
Uses lime as the binding material, which can be either fat lime or hydraulic lime.
- Fat lime shrinks to a great extent and hence it requires about 2-3 times its volume of sand.
- Lime should be slaked before use.
- Lime mortar is unsuitable for waterlogged areas or in damp situations.
- For hydraulic lime, the proportion of lime to sand by volume is about 1:2.
- Lime mortar has high plasticity and can be placed easily.
- It shrinks very little.
- It is sufficiently durable.
- It hardens slowly
2. Surkhi Mortar:
Made by using fully burnt Surkhi (type of finely powdered burnt clay) instead of sand or replacing half the sand in fat lime mortar. It is used for ordinary masonry work in foundations and superstructures but is not suitable for plastering or pointing as it may disintegrate over time.
3. Cement Mortar:
Uses cement as the binding material. The proportion of cement to sand by volume varies from 1:2 to 1:6 or more, depending on strength requirements. It is ideal for high-strength and water-resistant applications like underground constructions and water-saturated soils.
4. Gauged Mortar:
A combination of lime and cement to improve quality and achieve early strength. The usual proportion of cement to lime by volume is about 1:6 to 1:8. Also known as composite mortar or lime-cement mortar, it is used for bedding and thick brick walls.
- Makes 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 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.
3. Special Mortars
Special mortars have unique properties for specific applications:
I. Fire Resistant Mortar
This mortar is prepared by adding aluminous cement to finely crushed powder of fire bricks.
- The usual proportion is 1-part aluminous cement to 2 parts powder of fire bricks.
- This mortar is fire-resistant and is therefore used with fire bricks for lining furnaces, fireplaces, ovens, etc.
II. Lightweight Mortar
This mortar is prepared by adding materials such as sawdust and wood powder to lime mortar or cement mortar.
- Other materials that may be added include asbestos fibers, jute fibers, coir, etc.
- This mortar is used in soundproof and heatproof construction.
III. Packing Mortar
Special mortar is used for packing oil wells. It possesses high homogeneity, water resistance, and the ability to form solid waterproof plugs in cracks and voids of rocks.
Do You Knows?
The composition of packing mortar is decided by considering the hydrogeologic conditions, packing methods, and type of timbering.
IV. Sound Absorbing Mortar
To reduce noise levels, sound-absorbing plaster is formed using sound-absorbing mortar.
Here are some, Key Points to Remember, Related to the Mortar,
- Heavy Mortars: Bulk density of 15 kN/m³ or more.
- Lightweight Mortars: Bulk density less than 15 kN/m³.
- Lime Mortar: High plasticity, durable, but slow to harden.
- Surkhi Mortar: Suitable for masonry work but not for plastering.
- Cement Mortar: High strength and water resistance.
- Gauged Mortar: Economical and strong, used for thick walls.
- Fire Resistant Mortar: Ideal for fire-resistant applications.
Properties and Uses of a Good Mortar
A good mortar should possess the following properties:
- Adhesion: It should develop good adhesion with building units such as bricks and stones.
- Strength: It should be capable of developing the designed stresses.
- Cost-effectiveness: It should be economical.
- Durability: It should be durable and long-lasting.
- Workability: It should be easy to work with.
- Quick Setting: It should set quickly to speed up construction.
- Compatibility: It should not affect the durability of materials with which it comes into contact.
- Crack Resistance: The joints formed by mortar should not develop cracks and should maintain their appearance for a long time.
Uses of Mortar
Mortar is used in various construction applications, including:
- Binding Building Units: To bind building units such as bricks and stones.
- Plastering and Painting: To carry out painting and plaster work on exposed surfaces of masonry.
- Bedding Layer: To form an even and soft bedding layer for building units.
- Pipe Joints: To form joints in pipes.
- Aesthetic Improvement: To hide open joints of brickwork and stonework and improve the general appearance of the structure.
Important Consideration
Did You Know?
The setting action of mortar is affected by the presence of frost. It is advisable to stop work in frosty weather or to use cement mortar, which will set before it begins to freeze.
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