What is an Engineering Brick?

Engineering bricks are traditionally used in civil engineering as the foundation of buildings and to withstand damp climates, with a special manufacturing process that grants them superior strength. While traditional clay bricks are reliable and affordable options for many applications, they can be unsuitable for some heavy-duty projects. Moreover, heavy loads and wet environments deteriorate regular clay bricks and require a stronger alternative.

Lontto is a brick and block-making machine supplier with over 30 years of experience in engineering brick-making solutions. We’ve outlined a guide for understanding what an engineering brick is, how they are made, different types of engineering bricks, and how they are used.

Key Takeaways

• Engineering bricks are stronger than facing bricks, boasting a high compressive strength and low water absorption rate, so they can be used as the foundations of buildings in damp environments.
• There are two types of engineering bricks: Class A and Class B.
• Manufacturing engineering bricks requires high-quality clay (high iron oxide, low limestone) to be fired in a kiln at high temperatures, resulting in high strength bricks.
• Engineering bricks have multiple civil industry uses, including sewer tunnels, industrial furnaces, and load-bearing foundation.

What are the Properties of Engineering Bricks?

Engineering bricks are often used in structural engineering projects that require strength and resistance is required. Here’s everything you need to know about why engineering bricks are often preferred over regular facing bricks.

High Compressive Strength

Engineering bricks have a compressive strength of up to 100 N/mm², which is double the amount that regular facing bricks can withstand (around 50 N/mm²). This makes them an excellent choice for civil work where high strength and durability is needed, as in the foundation of a multistory building. The foundations of the Empire State Building, for example, were created using engineering bricks.

Low Water Absorption

Industrialists also use engineering bricks for their damp-proof properties, where facing bricks would perform poorly when in regular contact with water. The water absorption rate of engineering bricks is up to 4%, which prevents them from eroding quickly and stops damp from affecting the other building materials. This resistance to water also extends to frost resistance, which stops these bricks from deteriorating in the freezing-thaw cycle.

Durable Resilience

In addition to superior compressive strength and low water absorption, engineering bricks offer higher overall resilience against many other erosive factors in civil engineering. Engineering bricks have excellent resistance to chemicals and general weathering. They are also fire-resistant, making them a great choice for furnaces and other high-temperature settings.

How are Engineering Bricks Made?

To reach the level of strength and low porosity required for brick buildings, these bricks are produced in a high temperature kiln after being sourced and shaped into a resilient form. Here is the process that makes engineering bricks suitable for use:

1. Clay Mixing

The type of clay that is used to make engineering bricks is important. Clay with a naturally high iron-oxide content and a low lime content is ideal. The high oxide strengthens the brick and gives it its distinctive reddish color, while a low lime content prevents the brick from becoming too brittle after being fired in the kiln.

Commonly, shale and fireclay are combined until the mixture can be poured into the mold.

2. Shaping

The mixture is molded into bricks either by pressing or extrusion until they form the iconic brick design, similar to the type of brick you would see loose on a construction site. The bricks are cut and then dried, with any excess removed before the brick is fired in the kiln.

3. Kiln Firing

When the engineering bricks are ready and cut to the correct brick lengths, they are placed in the kiln to be fired (baked). The kiln is heated up to very high temperatures, between 1832° F and 2192° F (1000° C to 1200° C), and maintained to ensure that all parts of the brick are heated evenly. The bricks are then slowly cooled to limit any potential cracking.

Types of Engineering Bricks

Engineering bricks are divided into two classes: Class A and Class B. These classifications were originally developed in the United Kingdom. Here are the main differences between them:

Class A Engineering Bricks

Class A engineering bricks are the stronger classification, with a compressive strength of 125 N/mm². They also absorb less than 4.5% of water, which makes them excellent for civil projects like damp-proof courses. Typically, Class A engineering bricks are blue or red.

Class B Engineering Bricks

Class B engineering bricks are not as strong as their Class A counterparts, but are still much stronger than regular facing bricks. They have a compressive strength of 75 N/mm² and absorb less than 7% of water. While they do not match the high strength and water absorption of Class A bricks, Class B bricks are cheaper and are generally easier to source.

Uses and Applications

Engineering bricks are used in civil engineering projects where their high strength and low water absorption can be fully leveraged. While the use of these bricks can vary, you’ll most often see Class A and Class B bricks being used in the following construction projects:

• Building Foundations: Engineering bricks’ high compressive strength supports extremely heavy loads. This can be seen as the foundation for building groundworks and other multistory structures in the construction industry.
• Sewers: For water-facing structures like sewer tunnels, canal walls, and bridges, engineering bricks offer the low porosity required to protect against rising damp.
• Retaining Walls: In agricultural structures, engineering bricks are typically used to withstand soil pressure.
• Industrial Furnaces: Engineering bricks can bear the high temperatures and harsh chemicals found in industrial settings, such as chimneys and furnaces.
• Civil Engineering: For certain engineering work, engineering bricks are ideal for use in aggressive environments that require high strength and low porosity.

If you want more information about how Lontto can provide your business with advanced brick-making solutions, feel free to contact us! Get machine pricing today and receive a price quote from us within 1 working day.

FAQs on Engineering Bricks

Can Engineering Bricks Be Used for External Walls?

Yes, engineering bricks can be used in external walls. However, engineering bricks are more expensive than facing bricks, so using them for external walls is not suitable for every project.

They are most often seen as the load-bearing foundation of buildings and damp-proof courses.

Can You Lay Engineering Bricks in the Rain?

No, you cannot lay engineering bricks in the rain. While engineering bricks have a low water absorption rate or porosity, it is still not advised to lay any construction bricks during rainy conditions. Newly laid bricks mixed with water can soften the concrete that binds them and ruin the foundation of your structure.

Are Engineering Brick Dimensions Larger Than Facing Bricks?

While engineering bricks are stronger than regular facing bricks, they typically share the same dimensions (215 mm x 102.5 mm x 65 mm). This is a standardized engineering brick size that allows the bricks to be used in combination with facing bricks seamlessly.

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