Types of bricks in masonry construction: properties and uses

Bricks are a fundamental construction material, prized for their affordability and longevity. Available in rectangular shapes, they come in various compositions including clay, concrete, lime and fly ash.

Primary brick categories

Sun dried or unburnt clay bricks

These bricks involve three manufacturing steps: clay preparation, moulding and air drying in sunlight. They lack significant durability and water or fire resistance, making them unsuitable for permanent structures.

Burnt clay bricks

This category divides into four classes based on quality.

• First class: produced by table moulding and kiln burning, with standard shapes, sharp edges and smooth surfaces. This is the most durable and costly class.

• Second class: ground moulded bricks with uneven shapes and rough surfaces that require plaster finishing.

• Third class: poor quality bricks unsuitable for rainy climates, used only in temporary structures.

• Fourth class: over burnt, brittle bricks that are converted to concrete aggregate rather than used structurally.

Fly ash bricks

Made from fly ash and water, these bricks show self cementing properties due to their calcium oxide content. They offer superior fire insulation, uniform sizing, lower water penetration and do not require pre-soaking.

Concrete bricks

Manufactured from cement, sand, coarse aggregates and water. Advantages include on-site production capability, reduced mortar needs and colour customisation options.

Engineering bricks

High compressive strength materials for demanding applications requiring frost and acid resistance, commonly used in basements and damp proof courses.

Sand lime (calcium silicate) bricks

Constructed from sand and lime, used for decorative and masonry applications.

Quality standards at construction sites

Quality bricks generally show the following characteristics.

• Uniform, bright colouring

• Smooth surfaces with sharp edges

• Low thermal conductivity and sound dampening properties

• Maximum 20 percent water absorption when submerged

• A ringing sound when struck together

• Ability to withstand a 1 metre drop without breaking

• No scratch marks from fingernails

• No white deposits after 24 hours of soaking in water

Essential brick properties

Hardness: resistance to abrasion that ensures structural permanence.

Compressive strength: load capacity per unit area, with BIS standards requiring a minimum of 3.5 N/mm².

Absorption rates by classification:

• Heavy duty: 5 percent

• First class: 20 percent

• Second class: 22 percent

• Third class: 25 percent

Application uses

Higher grade bricks, first and second class, serve permanent structures including buildings, tunnels and pitched works. Lower grades and unburnt varieties suit temporary constructions, while fourth class materials function as concrete aggregate.