Concrete

Concrete in Construction Industries 

     Concrete is one of the most durable building materials. It provides superior fire resistance, compared with wooden construction and can gain strength over time. Structures made of concrete can have a long service life. Concrete is the most widely used construction material in the world with annual consumption estimated at between 21 and 31 billion tones.

     Concrete is used more than any other man-made material in the world. As of 2006, about 7.5 billion cubic meters of concrete are made each year—more than one cubic meter for every person on Earth.

    Concrete powers a US$35 billion industry, employing more than two million workers in the United States alone More than 55,000 miles (89,000 km) of highways in the United States are paved with this material. Reinforced concrete, pre-stressed concrete and precast concrete are the most widely used types of concrete functional extensions in modern days.

      

Precast Concrete Products

• Energy requirements for transportation of concrete are low because it is produced locally from local resources, typically manufactured within 100 kilometers of the job site. Similarly, relatively little energy is used in producing and combining the raw materials (although large amounts of CO2 are produced by the chemical reactions in cement manufacture). The overallembodied energy of concrete is therefore lower than for most structural materials other than wood.
• Once in place, concrete offers significant energy efficiency over the lifetime of a building. By storing and releasing the energy needed for heating or cooling, concrete's thermal mass delivers year-round benefits by reducing temperature swings inside and minimizing heating and cooling costs. While insulation reduces energy loss through the building envelope, thermal mass uses walls to store and release energy. Modern concrete wall systems use both external insulation and thermal mass to create an energy-efficient building. 
• Concrete buildings are more resistant to fire than those constructed using wood or steel frames, since concrete does not burn. Concrete reduces the risk of structural collapse and is an effective fire shield, providing safe means of escape for occupants and protection for fire fighters.
• Concrete also provides the best resistance of any building material to high winds, hurricanes, tornadoes due to its lateral stiffness that results in minimal horizontal movement.As discussed above, concrete is very strong in compression, but weak in tension. Larger earthquakes can generate very large shear loads on structures. These shear loads subject the structure to both tensional and compressional loads. Concrete structures without reinforcing, like other unreinforced masonry structures, can fail during severe earthquake shaking. Unreinforced masonry structures constitute one of the largest earthquake risks globally.These risks can be reduced through seismic retrofitting of at-risk buildings such as School buildings in Istanbul.

Concrete compound

 

Cement - Fine Aggregate -Coarse Aggregate

Cement

     Cement is the most significant compound in concrete. This is because its characteristic while react with water particle, beside getting harden, cement act as binder particles "glue" the mixture together to form a synthetic conglomerate. In fact, cement was introduced into two types, which is hydraulic and non-hydraulic.

      Hydraulic cements (e.g., Portland cement) are harden because of hydration process, chemical reactions that occur independently of the mixture's of water content; they can be harden even underwater or even constantly exposed to moisture weather.

The chemical reaction that results when the anhydrous cement powder is mixed with water produces hydrates that are not water-soluble. Non-hydraulic cements (e.g. gypsum plaster) must be kept dry in order to retain their strength. More about cement: 

Aggregate

     Aggregate was introduced in two type,one is fine aggregate another is course aggregate. To differentiate these two type aggregate is using sieve analysis, any soil particle which can pass through 5mm diameter sieve is consider fine aggregate, however, soil particle cannot pass through 5mm diameter sieve is considered course aggregate.

     Aggregates are added to cement with water to form concrete in certain ratio. Usually, aggregates occupy about 60-80 % of total concrete volume. One of the reasons adding aggregate to concrete mixture is to gain higher compressive strength as well as providing durability to concrete.

     Besides, aggregates are able to reduce heat output and therefore reduce thermal stress while reduce the shrinkage of concrete during temperature change due to different seasons. Officially, construction industries hope to reduce cost by adding aggregate to concrete, even some will change the mixture ratio to save more modal on construction.

Concrete Production Process

Concrete Production Process

• Preparing Material

     The limestone, silica, and alumina that make up Portland cement are dry ground into a very fine powder, mixed together in predetermined proportions, preheated, and calcined (heated to a high temperature that will burn off impurities without fusing the ingredients). Next, the material is burned in a large rotary kiln at 2,550 degrees Fahrenheit (1,400 degrees Celsius). At this temperature, the material partially fuses into a substance known as clinker. A modern kiln can produce as much as 6,200 tons of clinker a day.
     The clinker is then cooled and ground to a fine powder in a tube or ball mill. A ball mill is a rotating drum filled with steel balls of different sizes (depending on the desired fineness of the cement) that crush and grind the clinker. Gypsum is added during the grinding process. The final composition consists of several compounds which are tri-calcium silicate, dicalcium silicate, tri-calcium aluminate, and tetracalcium aluminoferrite.

• Mixing 

     The cement is then mixed with the other ingredients: aggregates (sand, gravel, or crushed stone), admixtures, fibers, and water. Aggregates are pre-blended or added at the ready-mix concrete plant under normal operating conditions. The mixing operation uses rotation or stirring to coat the surface of the aggregate with cement paste and to blend the other ingredients uniformly. A variety of batch or continuous mixers are used.
     Fibers, if desired, can be added by a variety of methods including direct spraying, premixing, impregnating, or hand laying-up. Silica fume is often used as a dispersing or densifying agent.

• Transport to work site

     Once the concrete mixture is ready, it is transported to the work site. There are many methods of transporting concrete, including wheelbarrows, buckets, belt conveyors,
     The first step in making concrete for the purpose to prepare the cement. One type of cement, Portland cement, is considered superior to natural cement because it is stronger, more durable, and of a more consistent quality.
     To make it, the raw materials are crushed and ground into a fine powder and mixed together. Next, the material undergoes two heating steps—calcining and burning. In calcining, the materials are heated to a high temperature but do not fuse together. In burning, however, the materials partially fuse together, forming a substance known as "clinker." The clinker is then ground in a ball mill—a rotating steel drum filled with steel balls that pulverize the material.
      After the Portland cement is prepared, it is mixed with aggregates such as sand or gravel, admixtures, fibers, and water. Next, it is transferred to the work site and placed. During placing, segregation of the various ingredients must be avoided so that full compaction—elimination of air bubbles—can be achieved. Pumping transports large quantities of concrete over large distances through pipelines using a system consisting of a hopper, a pump, and the pipes. Pumps come in several types—the horizontal piston pump with semi-rotary valves and small portable pumps called squeeze pumps. A vacuum provides a continuous flow of concrete, with two rotating rollers squeezing a flexible pipe to move the concrete into the delivery pipe.

• Placing and compacting

     Once at the site, the concrete must be placed and compacted. These two operations are performed almost simultaneously. Placing must be done so that segregation of the various ingredients is avoided and full compaction—with all air bubbles eliminated—can be achieved. Whether chutes or buggies are used, position is important in achieving these goals. The rates of placing and of compaction should be equal; the latter is usually accomplished using internal or external vibrators. An internal vibrator uses a poker housing a motor-driven shaft. When the poker is inserted into the concrete, controlled vibration occurs to compact the concrete. External vibrators are used for precast or thin insitu sections having a shape or thickness unsuitable for internal vibrators. These type of vibrators are rigidly clamped to the formwork, which rests on an elastic support. Both the form and the concrete are vibrated. Vibrating tables are also used, where a table produces vertical vibration by using two shafts rotating in opposite directions.

• Curing

     Once it is placed and compacted, the concrete must cured before it is finished to make sure that it doesn't dry too quickly. Concrete's strength is influenced by its moisture level during the hardening process: as the cement solidifies, the concrete shrinks. If site constraints prevent the concrete from contracting, tensile stresses will develop, weakening the concrete. To minimize this problem, concrete must be kept damp during the several days it requires to set and harden.

Concrete Degradation

     Concrete can be damaged by many processes, such as the expansion of corrosion products of the steel reinforcement bars, freezing of trapped water, fire or radiant heat, aggregate expansion, sea water effects, bacterial corrosion, leaching, erosion by fast-flowing water, physical damage and chemical damage (from carbonation, chlorides, sulfates and distillate water).


Impact on Environmentally 
     The environmental impact of concrete is a complex mixture of not entirely negative effects. A major component of concrete is cement, which has its own environmental and social impacts.
     The cement industry is one of two primary producers of carbon dioxide, a major greenhouse gas. Concrete is used to create hard surfaces which contribute to surface runoff, which can cause heavy soil erosion, water pollution and flooding. Concrete is a primary contributor to theurban heat island effect, but is less so than asphalt.
     Concrete dust released by building demolition and natural disasters can be a major source of dangerous air pollution. The presence of some substances in concrete, including useful and unwanted additives, can cause health concerns due to toxicidity and radioactivity. Wet concrete is highly alkaline and must be handled with proper protective equipment.



Modern Method of Consuming Concrete –Recycle

     Concrete recycling is an increasingly common method of disposing of concrete structures. Concrete debris was once routinely shipped to landfills for disposal, but recycling is increasing due to improved environmental awareness, governmental laws and economic benefits.
     Concrete, which must be free of trash, wood, paper and other such materials, is collected from demolition sites and put through a crushing machine, often along with asphalt, bricks and rocks.
     Reinforced concrete contains rebar and other metallic reinforcements, which are removed with magnets and recycled elsewhere. The remaining aggregate chunks are sorted by size. Larger chunks may go through the crusher again. Smaller pieces of concrete are used as gravel for new construction projects. Aggregate base gravel is laid down as the lowest layer in a road, with fresh concrete or asphalt placed over it. 
     Crushed recycled concrete can sometimes be used as the dry aggregate for brand new concrete if it is free of contaminants, though the use of recycled concrete limits strength and is not allowed in many jurisdictions. On 3 March 1983, US government funded research team approximated that almost 17% of worldwide landfill was by-products of concrete based waste.

Blocks

History of Blocks  

Blocks

   A concrete block can be used as a building material in the construction of walls. It is also defined as a concrete masonry unit (CMU). A concrete block is one of several precast concrete products used in construction. Most concrete blocks have one or more hollow cavities, and their sides may be cast smooth or with a design. Concrete blocks are stacked one at a time and held together with fresh concrete mortar to form the desired length and height of the wall.

     Concrete mortar was used by the Romans as early as 200 B.C. to bind shaped stones together in the construction of buildings. During the reign of the Roman emperor Caligula, small blocks of precast concrete were used as a construction material in the region around present-day Naples, Italy.  The English stonemason Joseph Aspdin developed portland cement, which became one of the key components of modern concrete from the year of 1824.

     In 1890, the first hollow concrete block is designed by Harmon S. Palmer in the United States. Palmer's blocks were 8 inches by 10 inches by 30 inches. They were so heavy. Therefore, they had to be lifted into place with a small crane. There is an estimated number which is 1,500 companies were manufacturing concrete blocks in the United States by the year of 1950.

     These early blocks were usually cast by hand. The average output was about 10 blocks per person per hour. Nowadays, concrete block manufacturing is a highly automated process that can produce up to 2,000 blocks per hour.

    Blocks are generally larger than bricks in term of size. Due to this reason, a block normally requires both hands to lift it up for laying process. For the same reason, it can be laid more quickly than bricks, but the larger size also means less versatility in laying process especially when structure ends, corners and laying to curves. Thus, blocks are generally intended to be plastered.

There are 2 types of blocks, which are clay blocks and concrete blocks where concrete blocks are more widely used.

Manufacture Process:

• Concrete  or clay is casted into mould, vibrated and cured.
• The addition of aluminium powder to a fine mix of sand, lime, fly ash and Portland cement are form most aerated blocks
• The dissolution of the metal powder produces a non-interconnecting cellular structure is to generate the hydrogen gas.
• The process is accelerated by pressure steam curing in an autoclave.

CONCRETE BLOCKS 

Type of concrete block:

• Solid

Solid concrete blocks are also called dense aggregate blocks. Solid concrete blocks are mostly used in the work-horse of the construction industry. Their distinctive properties of durability and strength make them an ideal and cost-effect solution for all types of load bearing walls

• Cellular

It can be defined as lightweight aggregate block. Produced in greater volume, but less strong than solid concrete blocks, cellular concrete blocks are used in both internal and external walls where loading is slightly more restricted or as infill blocks in beam and block flooring. Their main advantage over solid concrete blocks comes from a combination of higher insulating properties and a lighter unit weight. The cellular block enables time and material cost savings through easier handling and larger units.

• Hollow

It is known as aerated concrete or "aircrete" block. Hollow concrete blocks are the lightest weight among all types  the concrete blocks.  They are distinguished by their capacity to perform a dual structural / insulation function.  Though, it is limited to the structural applications in low-rise construction and partitions as well  as a component of curtain walling in higher buildings, hollow concrete blocks can perform a similar range of functions as solid and cellular concrete blocks.

Properties:

1.      Density and Strength

For the British Standard BS 6073-2: The range of aircrete and aggregate concrete blocks can be listed by common compressive strengths of 2.9, 3.6, 7.3, 8.7, 10.4, 17.5, 22.5, 30.0, and 40.0MPa.

The majority of concrete blocks fall in the range from 2.8 to 30MPa, with associated densities of 420–2200 kg/m3 and thermal conductivities from 0.10 to 1.5W/mK at 3% moisture content.

In the range of 0.03-0.05% is considered to the drying shrinkages.

2.      Durability

Dense concrete blocks and certain aerated lightweight blocks are resistant to freeze conditions below damp-proof course (DPC) level.

3.      Fixability

Aerated and lightweight concrete blocks has a good background for fixings.

Nails to a depth of 50mm are efficiency in the light loads.

Wall plugs and proprietary fixings are suitable for the heavier loads.

Both of these two fixings should avoid the edges of the blocks.

4.      Thermal insulation

The limiting area-weighted U-value standard for wall elements in new building is 0.35W/m²K.

The range of 0.27-0.30W/m²K is to achieve the Target Emission Rate overall.

5.      Phase change material blocks

Phase change materials (PCMs) incorporated into aerated concrete blocks offer some additional thermal stability to the internal environment by absorbing excessive summer heat, which is then released during the cooler periods.

The phase change at 26^◦C effectively increases the thermal capacity of the lightweight blocks.

6.      Fire resistance

Solid unplastered 90mm blocks can achieve up to 60 minutes’ fire protection.

Certain 150mm and most 215mm solid blocks can achieve 360 minutes’ fire protection.

Therefore, concrete block offers good fire resistance.

7.      Sound insulation

Concrete blocks can achieve minimum airborne sound insulation of 45Rw dB for separating walls and 40Rw dB for internal bedroom or WC walls.

CLAY BLOCKS 

In general, clay blocks are extruded hollow units. It is manufactured with the same materials that used in production of clay bricks. Through the process of firing, these blocks are becoming dense, hard, and brittle which make them to be easily cut and fixed. During the manufacturing, clay is added with sand, straw or other recycled materials to enhance its unique properties as it is fired, dried and extruded. As the blocks are burned off during firing process, innumerable tiny holes and connecting pores are occurred which the air will be trapped these pores and it helps to resist against hear and reduce the sound transmission. Additionally, clay block is not only resisting against fire, yet it also resists against the insects attack. Clay blocks are highly eco-friendly materials as it has less environmental impact during their manufacturing process compare to other materials and it provides a very high insulation.

Types of Clay Blocks

• Fire-clay blocks 

Fire-clay blocks are combining structural strength, insulation and when externally rendered as well as moisture protection. For masonry clay honeycomb blocks, it can be used as single skins for external load bearing walls. Besides, for its internal part, it is usually finished directly with gypsum plaster. They are actually manufactured to natural, riven, and textured finish in a range of colours, which is including terracotta red, ochre, buff and blue as well as to high gloss or satin finish in pastel shades.

• Unfired-clay blocks 

Unfired-clay blocks are manufactured from clay and sometimes incorporating straw might be used for non-load bearing partition walls. These blocks are easily to cut and to create many architectural features. Due to this, it is normally finished with a skin coat of clay plaster. However, its internal walls are sufficiently strong to support shelving and other features. Apart from that, it is actually recyclable or biodegradable and it has advantage of absorbing the odours and stabilizing internal humidity as well as temperature by its natural absorption and release moisture and heat.

• Gypsum blocks 

Gypsum blocks are generally made from natural crystalline rock. It is generally used as non-load bearing partitions and internal insulation of walls. Additionally, they are actually good in sound insulation. Thus, they are used to infill rather than used as load-bearing wall. The sound insulation properties are in relation to its thickness and block density. 

Properties:

• Low density: 600 – 800 kg/m³
• Medium density: 800 – 1100 kg/m³
• High density: 1100 – 1500 kg/m³

Typical Clay Blocks

The minimum average compressive strengths for clay blocks are;

• Non-loadbearing walls/partitions              1.4 N/mm2
• Facing and common blocks                     2.8 N/mm2
• Blocks for loadbearing internal walls        2.8 N/mm2

Omni Blocks (Green Material)

Omni Block

Nowadays, there are some high-rise buildings started to use green materials as its main materials which will insure a return on their construction investment. One of the green materials to be used in construction is Omni Block, an insulated 'stand-alone' structural wall system. For its advantage, it does not require and furring strips, additional insulation, or sheetrock to complete the wall, even though numerous finishes are added for its aesthetic purpose. 

Properties:

Omni Block is re-engineered "age-old" regular cinder block with unique cells, which are easily filled with uniformly molded Expanded Polystyrene foam insulation inserts.

Its insulation inserts are manufactured using safe, clean, non-toxic, and non-polluting processes, which in turn, result in a product that is environmental friendly. Its raw material is a by-product of oil refinery waste. The Block units are manufactured utilizing inorganic elements that are in abundant supply and locally quarried. 

Bricks

History of Bricks

Bricks Wall

Archaeologists have found bricks in the Middle East dating 10,000 years ago. Scientists suggest that these bricks were made from mud left after the rivers in that area flooded. The bricks were moulded by hand and left in the sun to dry. Structures were built by layering the bricks using mud and tar as mortar. The ancient city of Ur (modern Iraq) was built with mud bricks around 4,000 B.C. The Bible (Exodus 1:14; 5:4-19) provides the earliest written documentation of brick production—the Israelites made bricks for their Egyptian rulers. These bricks were made of clay dug from the earth, mixed with straw, and baked in crude ovens or burned in a fire. Many ancient structures made of bricks, such as the Great Wall of China and remnants of Roman buildings, are still standing today. The Romans further developed kiln-baked bricks and spread the art of brick making throughout Europe.

The oldest type of brick in the Western Hemisphere is the adobe brick. Adobe bricks are made from adobe soil, comprised of clay, quartz, and other minerals, and baked in the sun. Adobe soil can be found in dry regions throughout the world, but most notably in Central America, Mexico, and the south western United States. The Pyramid of the Sun was built of adobe bricks by the Aztecs in the fifteenth century and is still standing. In North America, bricks were used as early as the seventeenth century. Bricks were used extensively for building new factories and homes during the Industrial Revolution. Until the nineteenth century, raw materials for bricks were mined and mixed, and bricks were formed, by manual labour. The first brick making machines were steam powered, and the bricks were fired with wood or coal as fuel. Modern brick making equipment is powered by gas and electricity. Some manufacturers still produce bricks by hand, but the majority are machine made.

Phases of Manufacturing Bricks

The manufacturing process has six general phases: 

1) mining and storage of raw materials, 

2) preparing raw materials, 

3) forming the brick, 

4) drying, 

5) firing and cooling and 

6) de-hacking and storing finished products.

Mining and Storage 

Surface clays, shales and some fire clays are mined in open pits with power equipment. Then the clay or shale mixtures are transported to plant storage areas.

Preparation

To break up large clay lumps and stones, the material is processed through size-reduction machines before mixing the raw material. Usually the material is processed through inclined vibrating screens to control particle size.

Forming

Tempering, the first step in the forming process, produces a homogeneous, plastic clay mass. Usually, this is achieved by adding water to the clay in a pug mill, a mixing chamber with one or more revolving shafts with blade extensions. After pugging, the plastic clay mass is ready for forming. There are three principal processes for forming brick: stiff-mud, soft-mud and dry-press.

• Stiff-Mud Process - In the stiff-mud or extrusion process, water in the range of 10 to 15 percent is mixed into the clay to produce plasticity. After pugging, the tempered clay goes through a dearing chamber that maintains a vacuum of 15 to 29 in. (375 to 725 mm) of mercury. De-airing removes air holes and bubbles, giving the clay increased workability and plasticity, resulting in greater strength. Next, the clay is extruded through a die to produce a column of clay. As the clay column leaves the die, textures or surface coatings may be. An automatic cutter then slices through the clay column to create the individual brick. Cutter spacings and die sizes must be carefully calculated to compensate for normal shrinkage that occurs during drying and firing.
• Soft-Mud Process - The soft-mud or molded process is particularly suitable for clays containing too much water to be extruded by the stiff-mud process. Clays are mixed to contain 20 to 30 percent water and then formed into brick in molds. To prevent clay from sticking, the molds are lubricated with either sand or water to produce “sand-struck” or “water-struck” brick. Brick may be produced in this manner by machine or by hand.
• Dry-Press Process - This process is particularly suited to clays of very low plasticity. Clay is mixed with a minimal amount of water (up to 10 percent), then pressed into steel molds under pressures from 500 to 1500 psi (3.4 to 10.3 MPa) by hydraulic or compressed air rams.

Drying

Wet brick from molding or cutting machines contain 7 to 30 percent moisture, depending upon the forming method. Before the firing process begins, most of this water is evaporated in dryer chambers at temperatures ranging from about 100 ºF to 400 ºF (38 ºC to 204 ºC). The extent of drying time, which varies with different clays, usually is between 24 to 48 hours. Although heat may be generated specifically for dryer chambers, it usually is supplied from the exhaust heat of kilns to maximize thermal efficiency. In all cases, heat and humidity must be carefully regulated to avoid cracking in the brick.

Hacking

Hacking is the process of loading a kiln car or kiln with brick. The number of brick on the kiln car is determined by kiln size. The brick are typically placed by robots or mechanical means. The setting pattern has some influence on appearance. Brick placed face-to face will have a more uniform colour than brick that are cross-set or placed face-to-back.

Firing

Brick are fired between 10 and 40 hours, depending upon kiln type and other variables. There are several types of kilns used by manufacturers. The most common type is a tunnel kiln, followed by periodic kilns. Fuel may be natural gas, coal, sawdust, and methane gas from landfills or a combination of these fuels.

Cooling

After the temperature has peaked and is maintained for a prescribed time, the cooling process begins. Cooling time rarely exceeds 10 hours for tunnel kilns and from 5 to 24 hours in periodic kilns. Cooling is an important stage in brick manufacturing because the rate of cooling has a direct effect on colour.

De-hacking

De-hacking is the process of unloading a kiln or kiln car after the brick have cooled, a job often performed by robots. Brick are sorted, graded and packaged. Then they are placed in a storage yard or loaded onto rail cars or trucks for delivery. The majority of brick today are packaged in self-contained, strapped cubes, which can be broken down into individual strapped packages for ease of handling on the jobsite. The packages and cubes are configured to provide openings for handling by forklifts. More info of bricks process on following videos:

TYPES OF BRICKS

There are literally thousands of different bricks, but they can be broken down into a handful of basic types. The vast majority are made from clay and are kiln-fired.        

Facing Bricks

It is quality and durable bricks with an attractive appearance for external use above ground. 

Wirecut

The clay is continuously extruded to a required size and shape and then cut into individual bricks by means of a wire; much like a cheese is cut by cheese wire.  There are thousands of variations of blocks in colour and texture. Usually the cheapest facings available as the manufacturing process are highly automated.  

Stock

The clay is wetted to a so-called "soft mud" and then moulded to shape, before being allowed to dry prior to firing in the kiln. Much of the process is automated. Tend to be slightly irregular in shape. It is usually a bit more expensive than wirecuts.

Handmade

Handmade bricks are usually made on a bench, in a mould, much as described above for a stock brick. Because the clay isn't firmly compacted by machine, each brick normally has distinctive creasing known as a 'smile'. It is very desirable, and the most expensive of the facings, but well worth it on prestige jobs. 

Fletton

Also known as 'London Bricks'. A unique facing brick manufactured from the Lower Oxford clay found only in SE England. This clay contains coal traces, which burn during firing, reducing the amount of fuel needed for the kiln, which not only keeps down costs but also produces some interesting effects in the bricks themselves.

Commons

A cheap 'fill' brick, designed to be utilitarian rather than attractive. It is having said that, some have a charm of their own and are perfectly fine for smaller jobs.  

Common Bricks

Engineering

The workhorses of the brick family. Tough, strong, hardwearing but not usually very pretty. They have excellent resistance to frost and to water, making them ideal for ground works, sewer works and retaining walls. You pay for the performance.

Engineered Bricks

Concrete or Calcium Silicate

Popular in areas where good brick-making clay is scarce. Some are, quite frankly, bloody awful, but others may be split-faced or have a pitched face to give an impression of being something other than boring concrete. Cheap and cheerful sums them up.  

Concrete and Calcium Silicate Bricks

Reclaimed

Salvaged bricks. Bricks rescued from old buildings and cleaned up, of a fashion. Their charm is undeniable, when laid by a good brickie, but there can be a high level of wastage. Many will be the old Imperial sizes (2 5/8" or 3") which are incompatible with the modern metric bricks (65mm).

TYPES OF BRICK BONDING

Brickwork can be constructed by various arrangement of bricks bonded to form an integrated structure. There are a few commonly used bond patterns:

• 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)

• 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 English Garden Wall bond.

• 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.

• 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.

• Raking Bond

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

• Strecher 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.

BENEFITS OF BRICKS

Bricks of course have been around for centuries proving their long lasting and durability attributes. But there are many other benefits that have stamped bricks as the premier building product for future housing construction. There have been many products that have come and gone after claiming to be worthwhile replacements for bricks.

• Minimal maintenance
• Termite resistant
• Solid, safe, and secure
• Investment
• Environmental sustainability
• Brickwork is cost effective
• Aesthetic qualities
• Thermal mass - warmer in winter, cooler in summer
• Noise Reduction