Bricks Bonding

The creative use of brick bonding in architecture, with or without contrasting or complementary brick colours, can have a dramatic effect on the appearance of a building.
In recent times stretcher bond has predominated, mainly because of the speed with which it can be laid in cavity wall construction. There are, however, other traditional methods which can be used to enrich large areas of brickwork, although extra cutting is needed.

 English Bond
Alternative courses of headers and stretchers; one header placed centrally above each stretcher. This is a very strong bond when the wall is 1 brick thick (or thicker)






Flemish Bond

Alternate bricks are placed as header and stretcher in every course. Each header is placed centrally between the stretcher immediately above and below. This is not as strong as the English bond at 1 brick thick

English Garden Wall Bond

An alternative version of English bond with header courses being inserted at every fourth or sixth course. This is a correspondingly weaker bond.

Flemish Garden Wall Bond

Like English Garden Wall bond, this was originally intended for use in solid walls which were required to be
fair faced both sides.
The number of stretchers is increased and three stretchers are laid to one header in each course.

Stretcher Bond

Originally used for single brick walls, now called 1/2 brick walls it became the obvious choice for cavity walls as less cutting was required.

Raking Bonds

Herringbone and diagonal bonds can be effective within an exposed framed construction, or contained within restraining brick courses.

Properties and Functional Performances of Brick

Bricks are made from clay by burning it at high temperatures. The action of heat gives rise to a sintering process that causes the clay particles to fuse and develops extremely strong ceramic bonds in the burnt clay bodies. Such bonds are highly stable. As a result, bricks can withstand the severe weathering actions and are inert to almost all normal chemical attacks.

 Strength
Bricks are well-known for their high compressive strength. Their compressive strength depends on:

1. the raw materials used,
2. the manufacturing process, and
3. the shape and size.

Bricks made by a de-aerated extruder and fired to sufficiently high temperature can easily withstand a compressive pressure exceeding 28 N/mm² (4,000 psi). They are suitable for almost all structural building applications

Aesthetic appeal
Brick possesses the natural and pleasant colours of burnt clay. Its colour formation is achieved through a complicate physical chemical reaction during the firing process. In contrast to colour of stained body, brick colour is permanent and will not be faded during weathering process. Different clay compositions, firing temperatures or kiln atmosphere can lead to different colours of the burnt products. By proper control of these factors, bricks can be made to exhibit endless variety of natural and attractive colours.

Besides its richness in colour, bricks can be made to various textures. It is the combination of colour and texture that gives brick such distinctive feature which is everlasting and meadows with age. In view of the high cost to maintain the appearance of a building, the unique features of brick become an unparalleled advantage to housing design.

Porosity
Porosity is an important characteristic of brick. In contrast to other moulded or pre-cast building materials, the porosity of brick is attributed to its fine capillaries. By virtue of the capillary effect, the rate of moisture transport in the brick is ten times faster than in other building materials. Moisture is released during day-time and re-absorbed during night-time. The ability to release and re-absorb moisture (a "breathing" process) by capillary effect is one of the most useful properties of brick that helps to regulate the temperature and humidity of atmosphere in a house. This distinctive property makes brick an admirable building material, particularly suitable for houses in the tropics. On the other hand, all porous materials are susceptible to chemical attacks and liable to contamination from weathering agents like rain, running water and polluted air. Porosity of building material is an important factor to consider in respect its performance and applications.

Experiment results show that bricks with water absorption rate at 8% is 10 times more durable in resisting salt attack than that with water absorption rate at 20%. Well burnt brick has a normal water absorption rate less than 10% in contrast to that of concrete block and cement mortar exceeding 15%. This explains why brick walls require comparatively minimum maintenance in the course of time.

To mitigate the adverse effects but at the same time retain the advantages associated with porosity, the rate of water absorption of facing bricks for masonry brickwork should preferable be maintained around 10%.

A rarely known property of brick is its initial rate of absorption (IRA). It is in fact the initial rate of absorption that plays a key role in affecting the strength of bond between bricks and mortar during bricklaying. High value of IRA tends to remove excessive water from the mortar rapidly and thus hampers the proper hydration of cement . Experiments show that and an increase of IRA from 2 kg/m²/min to 4 kg/m²/min reduces the strength of brickwork by 50%. Generally, bricks with IRA exceeding 2 kg/m²/min will gives rise to difficulties in laying using common cement mortars. Modern brick extruder with de-airing action produces denser brick with lower IRA.

Fire Resistance
Brick is inherent with excellent fire resistance. A 100 mm brickwork with 12.5 mm normal plastering will provide a fire-resistance of 2 hours and a 200 mm non-plastered brickwork will give a maximum rating of 6 hours for non-load bearing purposes. Brick can support considerable load even when heated to 1000^oC in contrast to concrete wall at only up to 450^oC due to loss of water of hydration.

It is a fact that the non-combustibility of brick helps to promote its use in building houses against fire. There have been numerous examples in the past that people chose to use bricks for their houses after a devastating fire that burned down the whole city. Perhaps the most famous instance is the great London Fire in 1666, after which the rebuilding was largely done if not entirely in brick.

Sound Insulation
Brick wall shows good insulation property due to its dense structure. The sound insulation of brickwork is generally 45 decibels for a 4-1/2 in. thickness and 50 decibels for a 9-in. thickness for the frequency range of 200 to 2,000 Hz.

Thermal Insulation
Brick generally exhibits better thermal insulation property than other building materials like concrete. Perforation can improve the thermal insulation property of bricks to some extent. Besides, the mass and moisture of bricks help to keep the temperature inside the house relatively constant. In other words, bricks absorb and release heat slowly and thus keep the house cool during daytime and warm during nighttime.

Energy saving of a brick house is remarkable. A study commissioned by the Brick Institute of America had demonstrated that a brick house can save energy up to 30% when compared to that built of wood.

A comparison of the thermal conductivities of various materials is given in table below:-

Typical Thermal Conductivities of Various Building Materials
Material	Btu/(sq.ft.-hr-F/in.)	W/mK
Sand & gravel aggregate (dry)	9.0	1.30
Cement Mortar	5.0	0.70
Concrete (1:4)	5.28	0.77
Concrete Block (1:5) (four Oval-core)	5.2	0.75
Concrete Block (1:10) (four Oval-core)	6.6	0.95
Solid Brick (density:1925kg/m3)	5.0	0.72
Perforated Brick (25% perforation density:1400kg/m3)	4.0	0.58

Wear resistance
The wear resistance of a substance depends on its particulate bonds. Bricks shows high wear resistance because of its extremely strong ceramic bonds formed by the effect of heat at high temperature.

 Efflorescence
Efflorescence is a phenomenon that soluble slats dissolved in water are carried, deposited and gradually accumulated on brick surfaces to form an unsightly scum. The soluble salts may be originated from the raw material of bricks. But in most cases, efflorescence is caused by salts from the external sources such as ground water, contaminated atmosphere, mortar ingredients and other materials in contacts with the bricks.

Flexibility in Applications
Brick is used for an extremely wide range of applications in an equally extensive range of building and engineering structures. In particular, it can be used for load bearing structures which greatly simply the construction process so as to save materials, time and labour. Besides, brick can be make into convenient shape and size to facilitate the construction work. It is very flexible and handy in application almost everywhere.

Durability
Brick is extremely durable and perhaps is the most durable man-made structural building materials so far. There has been numerous ancient brick-building standing for centuries as a testimony of the endurance of burnt-clay brick.

Types of Bricks

Stock Stock Bricks are a traditional type of brick with a slightly irregular shape made by using a mechanised moulding process known as soft mud moulding. A wide range of colours is available. In price, as well as style, stock bricks fall between the wirecuts and the handmades. This type of brick is currently one of the most popular.

Engineering Engineering Bricks are used for their performance characteristics rather than their appearance and are most suited for groundworks, manholes and sewers, retaining walls and other situations where strength and resistance to frost attack and water are the most important factor. Fletton Fletton Bricks, or Londons are only manufactured by Hanson Brick. They are made from deposits of Oxford clay. They are available in a wide range of colours and textures, and are particularly popular for matching existing brickwork.  Handmade Handmade Bricks are literally made by hand by skilled craftsmen throwing clay into moulds. Each brick is unique and they have a pleasing and distinctive appearance with a creased face (known as a smile) as well as longstanding durability - many of our most admired historic buildings were built with handmade bricks. They are very much the thing for prestige housing projects.  The labour intensive production process puts handmades at the top end of the price scale but they are most certainly an investment that will appreciate.

Re-Pressed Re-Pressed Bricks are wirecut bricks which are re-pressed to create a solid brick with very precise size tolerances and distinctive surface texture. Known as the 'Jacobean', this range is unique to Butterley and is a high quality product that can be used effectively in housing.

Special Shapes Special Shapes: Hanson Brick manufactures special shaped bricks to enhance the company's extensive range of facings. There are over 70 special shapes available from Hanson consisting of both standard and purpose made shapes which enable flexible design and the means to execute any imaginative design detail or decorative element. In addition, their use adds a high quality finish to brickwork, can provide extra durability and protection to vulnerable areas and can save time on-site by overcoming extensive hand cutting.

Wirecut Wirecut Facing Bricks are made by extrusion of a continuous column of clay which, as the name implies, is cut by the wire but not before the column has been textured. They are suitable for almost every type of application and are available in a wide range of colours and textures. The highly automated production process makes wirecuts relatively inexpensive compared to some other types of brick.

Introduction for Bricks

Bricks are one of the oldest known building materials dating back to 7000BC where they were first found in southern Turkey and around Jericho. The first bricks were sun dried mud bricks. Fired bricks were found to be more resistant to harsher weather conditions, which made them a much more reliable brick for use in permanent buildings, where mud bricks would not have been sufficient. Fired brick were also useful for absorbing any heat generated throughout the day, then releasing it at night.

The Ancient Egyptians also used sun dried mud bricks as building materials, evidence of which can still be seen today at ruins such as Harappa Buhen and Mohenjo-daro.

Bricks are more commonly used in the construction of buildings. Bricks can be made from variety of materials the most common being clay but also calcium silicate and concrete.

Good quality bricks have a major advantage over stone as they are reliable, weather resistant and can tolerate acids, pollution and fire. Bricks can be made to any specification in colour, size and shape which makes bricks easier to build with than stone. Brickwork is also much cheaper than cut stone work. However there are some bricks which are more porous and therefore more susceptible to dampness when exposed to water. For best results in any construction work, the correct brick must be chosen in accordance with the job specifications. 

Manufacturing Process of Bricks

The initial step in producing brick is crushing and grinding the raw materials in a separator and a jaw crusher. Next, the blend of ingredients desired for each particular batch is selected and filtered before being sent on to one of three brick shaping processes—extrusion, molding, or pressing, the first of which is the most adaptable and thus the most common. Once the bricks are formed and any subsequent procedures performed, they are dried to remove excess moisture that might otherwise cause cracking during the ensuing firing process. Next, they are fired in ovens and then cooled. Finally, they are dehacked—automatically stacked, wrapped with steel bands, and padded with plastic corner protectors.

Grinding, sizing, and combining raw materials

• 1 First, each of the ingredients is conveyed to a separator that removes oversize material. A jaw crusher with horizontal steel plates then squeezes the particles, rendering them still smaller. After the raw materials for each batch of bricks have been selected, a scalping screen is often used to separate the different sizes of material. Material of the correct size is sent to storage silos, and over-sized material goes to a hammermill, which pulverizes it with rapidly moving steel hammers. The hammermill uses another screen to control the maximum size of particle leaving the mill, and discharge goes to a number of vibrating screens that separate out material of improper size before it is sent on to the next phase of production.

Extrusion

• 2 With extrusion, the most common method of brick forming, pulverized material and water are fed into one end of a pug mill, which uses knives on a rotating shaft to cut through and fold together material in a shallow chamber. The blend is then fed into an extruder at the far end of the mill. The extruder usually consists of two chambers. The first removes air from the ground clay with a vacuum, thereby preventing cracking and other defects. The second chamber, a high-pressure cylinder, compacts the material so the auger can extrude it through the die. After it is compressed, the plastic material is forced out of the chamber though a specially shaped die orifice. The cross-section of the extruded column, called the "pug," is formed into the shape of the die. Sections of desired length are cut to size with rotating knives or stiff wires.

In molding, soft, wet clay is shaped in a mold, usually a wooden box. The interior of the box is often coated with sand, which provides the desired texture and facilitates removing the formed brick from the mold. Water can also be used to assist release. Pressing, the third type of brick forming, requires a material with low water content. The material is placed in a die and then compacted with a steel plunger set at a desired pressure. More regular in shape and sharper in outline than brick made with the other two methods, pressed bricks also feature frogs.

Chamfering the brick

• 3 Chamfering machines were developed to produce a furrow in brick for such applications as paving. These machines use rollers to indent the brick as it is being extruded. They are sometimes equipped with wire cutters to do the chamfering and cutting in one step. Such machines can produce as many as 20,000 units per hour.

Coating

• 4 The choice of sand coating, also applied as the brick is extruded, depends on how soft or hard the extruded material is. A continuous, vibrating feeder is used to coat soft material, whereas for textured material the coating may have to be brushed or rolled on. For harder materials a pressure roller or compressed air is used, and, for extremely hard materials, sand blasting is required.

Drying

• 5 Before the brick is fired, it must be dried to remove excess moisture. If this moisture is not removed, the water will burn off too quickly during firing, causing cracking. Two types of dryers are used. Tunnel dryers use cars to move the brick through humidity-controlled zones that prevent cracking. They consist of a long chamber through which the ware is slowly pushed. External sources of fan-circulated hot air are forced into the dryer to speed the process.
• 6 Automatic chamber dryers are also used, especially in Europe. The extruded bricks are automatically placed in rows on two parallel bars. The bricks are then fed onto special racks with finger-like devices that hold several pairs of bars in multiple layers. These racks are then transferred by rail-mounted transfer cars or by lift trucks into the dryers.

Firing

• 7 After drying, the brick is loaded onto cars (usually automatically) and fired to high temperatures in furnaces called kilns. In general, the cars that moved the bricks through the drying process are also used to convey them through the tunnel kiln. These cars are pushed through the kiln's continuously maintained temperature zones at a specific rate that depends on the material. The majority of kilns in the United States use gas as a fuel source, though a third of the brick currently produced is fired using solid fuels such as sawdust and coal. Tunnel kilns have changed in design from high-load, narrow-width kilns to shorter, lower-set wider kilns that can fire more brick. This type of design has also led to high-velocity, long-flame, and low-temperature flame burners, which have improved temperature uniformity and lowered fuel consumption.  After forming and coating, the bricks are dried using either tunnel dryers or automatic chamber dryers. Next, bricks are loaded onto cars automatically and moved into large furnaces called tunnel kilns. Firing hardens and strengthens the brick. After cooling, the bricks are set and packaged. 

Setting and packaging

• 8 After the brick is fired and cooled, it is unloaded from the kiln car via the dehacking process, which has been automated to the point where almost all manual brickhandling is eliminated. Automated setting machines have been developed that can set brick at rates of over 18,000 per hour and can rotate the brick 180 degrees. Usually set in rows eleven bricks wide, a stack is wrapped with steel bands and fitted with plastic strips that serve as corner protectors. The packaged brick is then shipped to the job site, where it is typically unloaded using boom trucks.

Composition of Bricks

Building bricks are a mixture of clay and sand which is mixed with water to create the correct consistency. Sometimes the bricks also have added lime, ash or organic matter which speeds up the burning of the brick. The clay mixture is then formed in moulds to the desired specification ready to be dried then burnt in the kiln. Clay: The properties and quality of bricks depend on the type of clay used. The most common form of clay used for everyday bricks, is that with a sandy consistency, silicate or alumina, which usually contains small quantities of lime or iron oxide. Silica, when added to pure clay in the form of sand, prevents cracking, shrinking and warping. If there is a large proportion of sand used in the mixture the brick will be more textured and shapely. An excess of sand, however, renders the bricks too brittle and destroys cohesion. 25% of silica is said to be advantageous. Iron oxide in the clay enables the silica and alumina to fuse and adds considerably to the hardness and strength of the bricks. The iron content of the brick is evident in the colour of the brick and can be used to add the colour red into the bricks. However a clay which burns to a red colour will provide a stronger brick than clay which burns to a white or yellow brick. The lime content in a brick has two different effects. It stops the raw brick from shrinking and drying out, and it also acts as a flux during burning which causes the silica to melt and creates the bond which binds all the components of the brick together. However, too much lime can cause the brick to melt and loose shape. Any amount of quicklime within a brick is detrimental to its quality and can cause the brick to split into pieces. For the best qualities of pressed brick the clay is carefully selected both colour and composition. Clay from different sources is also often mixed together to create the desired mixture.

History of Bricks

Bricks are one of the oldest known building materials dating back to 7000BC where they were first found in southern Turkey and around Jericho. The first bricks were sun dried mud bricks. Fired bricks were found to be more resistant to harsher weather conditions, which made them a much more reliable brick for use in permanent buildings, where mud bricks would not have been sufficient. Fired brick were also useful for absorbing any heat generated throughout the day, then releasing it at night
The Ancient Egyptians also used sun dried mud bricks as building materials, evidence of which can still be seen today at ruins such as Harappa Buhen and Mohenjo-daro. Paintings on the tomb walls of Thebes portray slaves mixing, tempering and carrying clay for the sun dried bricks. These bricks also consisted of a 4:2:1 ratio which enabled them to be laid more easily.
The Romans further distinguished those which had been dried by the sun and air and those bricks which were burnt in a kiln. Preferring to make their bricks in the spring, the Romans held on to their bricks for 2 years before they were used or sold. They only used clay which was whitish or red for their bricks.
Using mobile kilns, the Romans were successful in introducing kiln fired bricks to the whole of the Roman Empire. The bricks were then stamped with the mark of the legion who supervised the brick production. These bricks differed from other ancient bricks in size and shape. Roman bricks were more commonly round, square, oblong, triangular or rectangular. The kiln fired bricks were generally 1 or 2 Roman foot by 1 Roman foot, but with some larger bricks at up to 3 Roman feet. The Romans preferred this type of brick making during the first century of their civilisation and used the bricks for public and private buildings all over the empire.
The Greeks also considered perpendicular brick walls more durable than stone walls and used them for public edifices. They also realised how the modern brick was less susceptible to erosion than the old marble walls.
During the 12th century bricks were reintroduced to northern Germany from northern Italy. This created the brick gothic period which was a reduced style of Gothic architecture previously very common in northern Europe. The buildings around this time were mainly built from fired red clay bricks. Brick Gothic style buildings can be found in the Baltic countries Sweden, Denmark, Poland, Germany, Finland, Lithuania, Latvia, Estonia, Belarus and Russia. The brick gothic period can be categorized by the lack of figural architectural sculptures which had previously been carved in stone. The Gothic figures were impossible to create out of bulky bricks at that time, but could be identified by the use of split courses of bricks in varying colours, red bricks, glazed bricks and white lime plaster. Eventually special shaped bricks were introduced which would imitate the architectural sculptures.
During the renaissance and Baroque periods, exposed brick walls became unpopular and brickwork was generally covered by plaster. Only during the mid 18th century did visible brick walls again regain some popularity.

The ancient Jetavanaramaya stupa in Anuradhapura, Sri Lanka is one of the largest brick structures in the world. 

The world's highest brick tower of St. Martin's Church in Landshut, Germany, completed in 1500 

Bricks

A brick is a block of ceramic material used in masonry construction, usually laid using various kinds of mortar. It has been regarded as one of the longest lasting and strongest building materials used throughout history.

Bricks are more commonly used in the construction of buildings than any other material except wood. Brick and terracotta architecture is dominant within its field and a great industry has developed and invested in the manufacture of many different types of bricks of all shapes and colours. With modern machinery, earth moving equipment, powerful electric motors and modern tunnel kilns, making bricks has become much more productive and efficient. Bricks can be made from variety of materials the most common being clay but also calcium silicate and concrete. With clay bricks being the more popular, they are now manufactured using three processes soft mud, dry press and extruded. Also during 2007 the new ‘fly ash’ brick was created using the by-products from coal power plants.
Good quality bricks have a major advantage over stone as they are reliable, weather resistant and can tolerate acids, pollution and fire. Bricks can be made to any specification in colour, size and shape which makes bricks easier to build with than stone. Brickwork is also much cheaper than cut stone work. However there are some bricks which are more porous and therefore more susceptible to dampness when exposed to water. For best results in any construction work, the correct brick must be chosen in accordance with the job specifications.