10 Questions on … Bricks

10-questions-on-bricks

1. What is the history of bricks?
The oldest discovered bricks, originally made from shaped mud and dating to before 7500 B.C., were found at Tell Aswad, Syria. The first sun-dried bricks were made in Mesopotamia (what is now Iraq), in the ancient city of Ur in about 4000 BC.

The Romans made use of fired bricks, and the Roman legions, which operated mobile kilns, introduced bricks to many parts of the empire. Roman bricks are often stamped with the mark of the legion that supervised their production. The use of bricks in southern and western Germany, for example, can be traced back to traditions already described by the Roman architect Vitruvius.

2. How are they made?

Mud bricks – The soft mud method is the most common, due to the low costs of production. It starts with the raw clay, preferably in a mix with 25-30% sand to reduce shrinkage. The clay is first ground and mixed with water to the desired consistency, it is then pressed into steel moulds with a hydraulic press. The shaped clay is then fired (“burned”) at 900-1000° C to achieve strength.

Rail kilns – In modern brickworks, this is usually done in a continuously fired tunnel kiln, in which the bricks move slowly through the kiln on conveyors, rails, or kiln cars to achieve consistency for all bricks. The bricks often have added lime, ash, and organic matter to speed the burning.

There are several other ways which can be found at this link.

3. What has an affect on the brick’s colour?

The final colour of bricks is influenced by the chemical and mineral content of raw materials, the firing temperature and the atmosphere in the kiln. For example pink coloured bricks are the result of a high iron content, white or yellow bricks have a higher lime content. Most bricks burn to various red hues, if the temperature is increased the colour moves through dark red, purple and then to brown or grey at around 1,300° C (2,372° F). The names of bricks may reflect their origin and colour, such as London stock brick and Cambridgeshire White.

4. Are concrete blocks a form of brick?

Yes. “Bricks” formed from concrete are usually termed blocks, and are typically pale grey in colour. They are made from a dry, small aggregate concrete which is formed in steel moulds by vibration and compaction in either an “egglayer” or static machine. The finished blocks are cured rather than fired using low-pressure steam. Concrete blocks are manufactured in a much wider range of shapes and sizes than clay bricks and are also available with a wider range of face treatments – a number of which are to simulate the appearance of clay bricks.

5. What are bricks used for?

In the United Kingdom, bricks have been used in construction for centuries. Until recently, almost all houses were built almost entirely from bricks. Although many houses in the UK are now built using a mixture of concrete blocks and other materials, many houses are skinned with a layer of bricks on the outside for aesthetic appeal.

Bricks are used in the metallurgy and glass industries for lining furnaces, as well as on pavements, although this is now more for aesthetic quality as they have been found incapable of withstanding heavy traffic. They are also used as a method of traffic calming in some areas due to the unevenness of a brick laid surface. Many famous old streets, like the Royal Mile in Edinburgh, are ‘cobbled’ in this way.

6. How big is a standard brick?

The measurements of a standard house brick in the UK are:
215mm × 102.5mm × 65mm (8.5 x 4 x 2.5 inches)

7. What are the limitations of bricks?

Brick buildings can be prone to damage from earthquakes due to their rigidity and to the weakness of the mortar. During seismic events, the mortar cracks and crumbles, and the bricks are no longer held together.

8. What are the benefits of having a masonry (bricks/blocks and mortar) structure?

· It can increase the thermal mass of a building.
· Brick typically will not require painting and so can provide a structure with reduced maintenance costs.
· Masonry is very heat resistant and thus provides good fire protection.
· Masonry walls are resistant to projectiles, such as debris from hurricanes or tornadoes.
· Masonry structures built in compression preferably with lime mortar can have a useful life of more than 500 years as compared to 30 to 100 for structures of steel or reinforced concrete.

9. What are the disadvantages?

· Extreme weather causes degradation of masonry wall surfaces due to frost damage.
· This type of damage is common with certain types of brick, though rare with concrete blocks.
· Masonry tends to be heavy and must be built upon a strong foundation, usually reinforced concrete, to avoid settling and cracking.

10. Where might I find more information on bricks and masonry?

The Brick Development Association represents clay bricks and pavers. More information can be found on their website here. Additionally, bricksandbrass.co.uk provides a wealth of information on the history, types, materials etc. of bricks and brickwork.

27-09-11

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