Being one of the most important parts of Masonry construction, bricks carry a history of over 10,000 years with evidence found in the ruins of Mohenjo-daro and Buhen. They were originally made from clay which is a combination of earth or mud with a little hay added and then left to dry in the sun for days. Around 4000 B.C, the first of the sun dried bricks were made in Mesopotamia currently knows as Iraq; they were used as a sacred object in the “ritual of the first brick”. The oldest bricks in their pure form have been discovered in the region of Tigris dating back to 7500 B.C. On the other hand current and todays bricks happened to be…… In this report we will discuss blah blah blah.
Later Romans followed by making use of the fired bricks in the Roman legions using a moving kiln. This helped in introducing bricks to all parts of the empire; the bricks were often times marked with the stamp of the legion that supervised their production. This was proved in the western and southern part of Germany where the traditions of building are described by the Roman architect Vitruvius.
12th century Europe shows the beginning of domestic bricks, mostly used in Gothic Architecture. Northern Europe which has no actual rock foundation due to unavailability of rocks started using these bricks for progress. Visible bricks were quiet unpopular so they were plastered in white; later in the 18th century visible brick buildings started gaining popularity. Bricks were mostly manufactured close to the construction site but with time roads, railways, canals and heavy vehicles were used to transport them. The beginning of the 19th century brought about the construction of looming office buildings such as the Monadnock Building in Chicago as well as paved roads which eased transportation.
Modern day bricks have three main kinds of production processes which are soft mud, dry press and extrusion. Others do exist which vary from region to region. The constituents of a brick are:
• Silica ( Sand) * By weight 50% to 60%
• Alumina ( Clay) *By weight 20% to 30%
• Lime * By weight 2% to 5%
• Iron oxide *<7% by weight
• Magnesia * by weight, less than 1%
The most common method used for brick production is soft mud; the process starts with raw clay mixed with sand (25-30%) to reduce shrinking. The clay is initially grounded and mixed with water to create soft dough. At the desired softness it is then pressed into steel molds using a hydraulic press, then fired at about 900-1000’C. Now the kilns may vary as technology has advanced worldwide; modern kilns have conveyor belts for the bricks to move inside for even heating. In some parts of the world the old method of Bull’s trench Kilns is also used; this was invented in the 19th century by a British Engineer W. Bull.
Dry press is another method which starts with a much thicker clay mix so bricks with sharper edges and more accurate sizes are formed. The third process is Extrusion; clay is mixed with 10-15% water for stiff extrusion and 20-25% of water for soft extrusion. The material is then forced through a die (tool used to shape and cut) to ensure proper length and width of the bricks. After being cut and shaped, the bricks are left to dry for about 20 to 40 hours and then fired.
The most common brick types used around the world are:
• Stock: This uses the traditional molding process and is then burned in the kiln for hardening.
• Engineering: These are known for their light weight and strength performance; Ground work like manholes, sewers and retaining walls use these type of bricks.
• Fletton: These are only manufactured in London by Hanson Bricks and are distributed around the world. They are famous for their colors and strength.
• Handmade: These are literally made by hand, filled in steel molds and then burned.
• Re-pressed: These are wire cut bricks and are re-pressed to create a perfect shape and size; each brick is of the same weight, length and width.
• Special shapes: These come in custom and premade shapes and sizes, to add to the beauty of the building. There are about 70 different shapes and sizes available.
Pakistan has about 18,000 kilns spread across the country with 4.5 million workers working hard in them. One of the big names in the Kiln Industry is of Butt Brothers Brick Company; they have been manufacturing bricks since 1979. The company is not famous in Pakistan but has a clientele in Middle East, Europe, USA and South Africa.
The most common of the problems Bricks face these days are Efflorescence, Frost Attack, Lime Staining and Sulfate Attack. To begin with the most common of these is theEfflorescence which occurs when soluble salts get deposited on the brickwork. It’s a repeated process of drying and getting wet, as soon as the wall will get dry the salts will appear and as soon as moisture hits the salt will be there but in a transparent mode. This problem usually occurs when the brickwork is new or has received the first soaking. Although this can never be completely avoided but to minimize the risk good overhangs, copings and sills with drips are to be installed so this can be prevented.
Frost attack is always going to be there when after a cold cold weather the wet spell will hit the brick wall. When certain porous materials are saturated and the temperature drops below the freezing point the formation of ice will cause stress and certain bricks are not resistant to it and cracks and spalling will be seen. Only a few bricks are known to be Frost Resistant, and clay bricks are said to be that one type that can face the frost. To generally avoid the frost bite of the bricks the brick laying should not take place in freezing temperatures. Most particularly antifreeze agents used should be avoided as they do not work for a long time.
From the problems the bricks are facing these days the biggest and a far more serious one is Sulfate Attack. This happens when soluble sulfate salts react to certain types of cement and form calcium sulfoaluminate. The crystals that are formed are the reason of the cracking and the wall over all starts crumbling it then affects the strength and integrity of the wall. A special type of cement is available to prevent this kind of attack on the bricks and the cracking can be prevented. For further assistance, hire consultancy of AmerAdnan Associates today.