architecture

Categorizing Bricks by Raw Materials

In modern construction practices, bricks are categorized according to their component materials and method of manufacture. Under this classification, there are five common types:

• Burnt clay bricks
• Sand lime bricks (calcium silicate bricks)
• Concrete bricks
• Fly ash clay bricks
• Firebrick

Burnt Clay Bricks

Burnt clay bricks are the classic form of brick, created by pressing wet clay into molds, then drying and firing them in kilns. This is a very old building material—the type of brick found in many of the ancient structures of the world. In appearance, these bricks are solid blocks of hardened clay, usually reddish in color.

Burnt clay bricks are typically sold in four classes, with first-class offering the best quality and most strength. These high-grade burnt clay bricks have no noticeable flaws, but they’re also going to cost more.

When these bricks are used in walls, they require plastering or rendering with mortar. Uses for burnt clay bricks include:

• Masonry walls
• Foundations
• Columns

Sand Lime Bricks

Sand lime bricks (also known as calcium silcate bricks) are made by mixing sand, fly ash and lime. Pigments may also be added for color. The mixture is then molded under pressure to form bricks; the materials bond together by a chemical reaction that occurs as the wet bricks dry under heat and pressure. These bricks are not, however, fired in kilns in the same manner as burnt clay bricks. Sand lime bricks can offer some advantages over clay bricks such as:

• Their color appearance is gray instead of the regular reddish color.
• Their shape is uniform and presents a smoother finish that doesn’t require plastering.
• These bricks offer excellent strength for load-bearing structures.
• When pigments are added, the bricks can be used for ornamental purposes.
• Less mortar is required during construction.
• Edges are straight and precise, making construction easier.
• Bricks do not effloresce salts and minerals.

The uses for sand lime bricks include:

• Structural foundations and walls
• Exposed brick walls and pillars
• Ornamental uses (when pigments are added)

Concrete Bricks

This types of bricks are made from solid concrete and are growing in popularity among homeowners. Concrete bricks are usually placed in facades, fences, and provide an excellent aesthetic presence. These bricks can be manufactured to provide different colors if pigments are added during production. Concrete bricks should not be used in below-ground applications.

Common uses for concrete bricks include:

• Fences
• Internal (hidden) brickwork

Fly Ash Clay Bricks

Fly ash clay bricks are byproduct of coal burning—fired at about 1,000 degrees C. Because a high volume of calcium oxide, this type of brick is sometimes described as self-cementing, since it expands when exposed to moisture. This tendency to expand, however, can also produce pop-out failure. Fly ash clay brick has the advantage of being lighter in weight than clay or concrete brick.

Typical uses for fly ash clay brick include:

• Structural walls
• Foundations
• Pillars
• Anywhere that improved fire resistance is required

Fire Bricks

Also known as refractory bricks, these are manufactured from specially formulated earth with a high aluminum oxide content. After burning, these bricks can withstand very high temperatures without their shape, size, or strength being affected.

Common used for this type of brick include:

• Lining of chimneys and furnaces
• Pizza ovens and outdoor brick barbecues 

by Limult