Building materials
Building materials should have the following properties:
1) They must last over time, which means that they must be impervious to biological and chemical attack. This applies not only to their strength, but also to their appearance and color. Many building materials are known to discolour after years of exposure to the sun's ultraviolet (UV) rays. Therefore those materials used in construction must be UV stable. Materials that are only used indoors need not be UV stable.
Concrete can lose its strength over time if chemicals seep into it via rainwater or atmospheric pollution. It is especially susceptible to chloride attack. Steel can rust or corrode over time. Rusting has amajor impact on the load carrying abilityof a member, and can quickly make a structural member useless!
2) They must be strong. Every part of a building is subject to some level of force, and each part must be capable of carrying the loads that fall on it. Many building components have other components attached to them, like brackets, railings, light fixtures, pipes, ducts, and wall shelves. They must be able to hold on to and retain these attachments. Building materials can be rated for their compressive strength (think of bricks pressing down on each other), or tensile strength (like the force you exert on the chain of a swing when you stand on it), or both.
3) They must resist wear and tear. In the building industry, wear and tear is called abrasion resistance. It is especially important for areas like floor finishes, but every part of the building is subject to some level of abrasion, and must be able to resist this. You can actually measure how abrasion resistant a building material is by performing a standardized test such as a Taber Test. In this test, a metal disc of standardized design and weight is rotated against the material to be tested, at a standard speed for a fixed length of time. The material sample is weighed before and after the test. The difference in weight gives us an indication of how much material was lost during the test. The more the material lost, the less the abrasion resistance of the material. In this way you can compare, say, the abrasion resistance of a marble floor versus a ceramic tile and then decide which works best for that particular area.
You can also perform other tests, such as scratch resistance for building materials like glass or coated aluminum.
1) They must last over time, which means that they must be impervious to biological and chemical attack. This applies not only to their strength, but also to their appearance and color. Many building materials are known to discolour after years of exposure to the sun's ultraviolet (UV) rays. Therefore those materials used in construction must be UV stable. Materials that are only used indoors need not be UV stable.
Concrete can lose its strength over time if chemicals seep into it via rainwater or atmospheric pollution. It is especially susceptible to chloride attack. Steel can rust or corrode over time. Rusting has amajor impact on the load carrying abilityof a member, and can quickly make a structural member useless!
2) They must be strong. Every part of a building is subject to some level of force, and each part must be capable of carrying the loads that fall on it. Many building components have other components attached to them, like brackets, railings, light fixtures, pipes, ducts, and wall shelves. They must be able to hold on to and retain these attachments. Building materials can be rated for their compressive strength (think of bricks pressing down on each other), or tensile strength (like the force you exert on the chain of a swing when you stand on it), or both.
3) They must resist wear and tear. In the building industry, wear and tear is called abrasion resistance. It is especially important for areas like floor finishes, but every part of the building is subject to some level of abrasion, and must be able to resist this. You can actually measure how abrasion resistant a building material is by performing a standardized test such as a Taber Test. In this test, a metal disc of standardized design and weight is rotated against the material to be tested, at a standard speed for a fixed length of time. The material sample is weighed before and after the test. The difference in weight gives us an indication of how much material was lost during the test. The more the material lost, the less the abrasion resistance of the material. In this way you can compare, say, the abrasion resistance of a marble floor versus a ceramic tile and then decide which works best for that particular area.
You can also perform other tests, such as scratch resistance for building materials like glass or coated aluminum.
CONCRETE
When we say concrete in the building trade, we actually mean reinforced concrete. Its full name is reinforced cement concrete, or RCC. RCC is concrete that contains steel bars, called reinforcement bars, or rebars. This combination works very well, as concrete is very strong in compression, easy to produce at site, and inexpensive, and steel is very very strong in tension.
To make reinforced concrete, one first makes a mould, called formwork, that will contain the liquid concrete and give it the form and shape we need. Then one looks at the structural engineer's drawings and places in the steel reinforcement bars, and ties them in place using wire. The tied steel is called a reinforcement cage, because it is shaped like one. Once the steel is in place, one can start to prepare the concrete, by mixing cement, sand, stone chips in a range of sizes, and water in a cement mixer, and pouring in the liquid concrete into the formwork tilll exactly the right level is reached. The concrete will become hard in a matter of hours, but takes a month to reach its full strength. Therefore it is usually propped up until that period. During this time the concrete must be cured, or supplied with water on its surface, which it needs for the chemical reactions within to proceed properly. |
Working out the exact 'recipe', or proportions of each ingredient, is a science in itself. It is called concrete mix design. A good mix designer will start with the properties that are desired in the mix, then take many factors into account, and work out a detailed mix design. A site engineer will often order a different type of mix for a different purpose. For example, if he is casting a thin concrete wall in a hard-to-reach area, he will ask for a mix that is more flowable than stiff. This will allow the liquid concrete to flow by gravity into every corner of the formwork. For most construction applications, however, a standard mix is used. Common examples of standard mixes are M20, M30, M40 concrete, where the number refers to the strength of the concrete in n/mm2. Therefore M30 concrete will have a compressive strength of 30 n/mm2. A standard mix may also specify the maximum aggregate size. Aggregates are the stone chips used in concrete. If an engineer specifies M30 / 20 concrete, he wants M30 concrete with a maximum aggregate size of 20mm. He does NOT want concrete with a strength of between 20-30 n/mm2, which is a common misinterpretation in some parts of the world.
Concrete that is cast in place in its mould is called cast-in-situ concrete. Concrete members that are cast in a concrete factory and then shipped to site are called precast concrete.
Concrete that is cast in place in its mould is called cast-in-situ concrete. Concrete members that are cast in a concrete factory and then shipped to site are called precast concrete.
types of concrete
The most common types of concrete are:
High Strength Concrete: the most basic and important property of concrete is its compressive strength. Concrete with a compressive strength of 40Mpa (5,800 psi) is called high strength concrete.
High Performance Concrete: is a new term for some concretes being developed today. It is a fairly broad term that describes concretes that outperform "normal", everyday concrete in one or more characteristics such as lifespan, lifespan in corrosive environments, permeability, density, ease of placement, or many other parameters.
Lightweight Concrete: is made by using small, lightweight aggregates, such as small balls of styrofoam (thermocole) or by adding foaming agents to the mix of concrete. Lightweight concretes have low structural strength, and are used mostly in non-structural elements. The best is example is aerated autoclaved concrete (AAC) blocks used for making walls. Also called cellular concrete or aerated concrete.
Self Consolidating Concrete, also called Self Compacting Concrete:
Sprayed Concrete or Shotcrete: you can actually spray concrete onto a surface to form a thick, uneven coating. This process is different from other concreting methods in that the concrete is not poured into a form or mould. It is sprayed directly onto a surface, and is used in infrastructure projects and to repair old, cracked concrete surfaces. Shotcreting is also called guniting.
Water-resistant Concrete: normal concretes are permeable to water; that is, they allow water to pass through.Water resistant concretes are engineered to have fine particle cement replacements that do not allow water to pass through. These are very useful for construction below ground, like basements, as well as water retaining structures like water tanks and dams, and of course marine structures like jetties and bridges.
Micro reinforced concretes: are a new generation of high-tech concretes. They contain small steel, fibreglass or plastic fibres that dramatically alter the properties of concrete.
High Strength Concrete: the most basic and important property of concrete is its compressive strength. Concrete with a compressive strength of 40Mpa (5,800 psi) is called high strength concrete.
High Performance Concrete: is a new term for some concretes being developed today. It is a fairly broad term that describes concretes that outperform "normal", everyday concrete in one or more characteristics such as lifespan, lifespan in corrosive environments, permeability, density, ease of placement, or many other parameters.
Lightweight Concrete: is made by using small, lightweight aggregates, such as small balls of styrofoam (thermocole) or by adding foaming agents to the mix of concrete. Lightweight concretes have low structural strength, and are used mostly in non-structural elements. The best is example is aerated autoclaved concrete (AAC) blocks used for making walls. Also called cellular concrete or aerated concrete.
Self Consolidating Concrete, also called Self Compacting Concrete:
Sprayed Concrete or Shotcrete: you can actually spray concrete onto a surface to form a thick, uneven coating. This process is different from other concreting methods in that the concrete is not poured into a form or mould. It is sprayed directly onto a surface, and is used in infrastructure projects and to repair old, cracked concrete surfaces. Shotcreting is also called guniting.
Water-resistant Concrete: normal concretes are permeable to water; that is, they allow water to pass through.Water resistant concretes are engineered to have fine particle cement replacements that do not allow water to pass through. These are very useful for construction below ground, like basements, as well as water retaining structures like water tanks and dams, and of course marine structures like jetties and bridges.
Micro reinforced concretes: are a new generation of high-tech concretes. They contain small steel, fibreglass or plastic fibres that dramatically alter the properties of concrete.
STONE
Stone is a great floor finish and is affordable in many countries; Italy and India are both known for the variety and quality of stone they produce. There is a great advantage to stone that is almost unique to floor finishes: you can polish it, and thus make it look and feel like new, at any time in its life.
Granite is a volcanic rock (it was originally lava, that cooled to form solid rock) that has the following properties:
Its surface can also be worked to produce a variety of textures other than smooth: granite can be flamed, water blasted, sand blasted, bush hammered, or tumbled. These rough finishes are mostly used outdoors, on pathways. The famous cobblestones of Europe are granite, for instance.
Granite is a volcanic rock (it was originally lava, that cooled to form solid rock) that has the following properties:
- It is very hard, strong, and abrasion resistant
- It is resistant to acids
- It can be polished to a mirror-like smoothness
Its surface can also be worked to produce a variety of textures other than smooth: granite can be flamed, water blasted, sand blasted, bush hammered, or tumbled. These rough finishes are mostly used outdoors, on pathways. The famous cobblestones of Europe are granite, for instance.
Marble is a metamorphic rock (meaning that it was made by the intense pressures and heat deep within the earth), and has the following properties:
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Sandstone is a sedimentary rock (rock formed by ancient rivers that slowly deposited material on their beds, that built up layer by layer over millions of years). It has the following properties:
- It is abrasion resistant, but not always strong, as it is formed in layers.
- It is usually highly resistant to acids
- It has a rough finish, and cannot be mirror-polished, as it consists of grains
GLASS
Glass has been a fascinating material to humankind since it was first made in about 500 BC. At first thought to possess magical properties, glass has come a long way. It is one of the most versatile and oldest materials in the building industry. From its humble beginnings as a window pane in luxury houses of Pompeii to sophisticated structural members in new age buildings, its role in architecture has evolved over the years.
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a brief history of glass in the building industry
In prehistoric times, Obsidian (Naturally occurring glass found near volcanic regions) and fulgurite (glass formed naturally after lightning strikes sand) were used to make weapons. Manmade glass was used as a luxury material was used in decorations, jewelry, vessels and crockery.
Glass blowing was discovered in the 1st century in Europe, this revolutionized the glass making industry. The technique spread throughout the Roman Empire. Production of Clear glass, by introduction of manganese dioxide, saw glass being used for architectural purposes. Cast glass windows began to appear in the most important buildings and villas in Rome and Pompeii. Over the next 1,000 years glass making spread through all of Europe and Middle East. In 7th century Anglo Saxon glass was used in churches and cathedrals
By 11th century sheet glass was made by the crown glass process. In this process, the glassblower would spin molten glass at the end of a rod until it flattened into a disk. The disk would then be cut into panes. By 13th century, this technique was perfected in Venice. Stain glass windows were used in gothic renaissance and baroque architecture from the 11th to the 18th century. The examples of stunning patterns created by using colorful glass are immortalized by great artists all over the world.The Crown glass process was used up to the mid-19th century. in the 19th century, flat / sheet glass windows were used in making windows. These were completely flat and did not have any optical distortions.
But glass was still an item of luxury as it took large resources, brilliant skill and immense energy to be produced. In 1958 Pilkington and Bickerstaff introduced the revolutionary float glass process to the world. This method gave the sheet uniform thickness and very flat surfaces. Modern windows are made from float glass.
Glass blowing was discovered in the 1st century in Europe, this revolutionized the glass making industry. The technique spread throughout the Roman Empire. Production of Clear glass, by introduction of manganese dioxide, saw glass being used for architectural purposes. Cast glass windows began to appear in the most important buildings and villas in Rome and Pompeii. Over the next 1,000 years glass making spread through all of Europe and Middle East. In 7th century Anglo Saxon glass was used in churches and cathedrals
By 11th century sheet glass was made by the crown glass process. In this process, the glassblower would spin molten glass at the end of a rod until it flattened into a disk. The disk would then be cut into panes. By 13th century, this technique was perfected in Venice. Stain glass windows were used in gothic renaissance and baroque architecture from the 11th to the 18th century. The examples of stunning patterns created by using colorful glass are immortalized by great artists all over the world.The Crown glass process was used up to the mid-19th century. in the 19th century, flat / sheet glass windows were used in making windows. These were completely flat and did not have any optical distortions.
But glass was still an item of luxury as it took large resources, brilliant skill and immense energy to be produced. In 1958 Pilkington and Bickerstaff introduced the revolutionary float glass process to the world. This method gave the sheet uniform thickness and very flat surfaces. Modern windows are made from float glass.
how glass is used in construction
From the beginning of 20th century modern architecture has been instrumental in mass production of concrete, glass and steel buildings in the factories we call cities. This ideology helped accommodate housing needs of the burgeoning middle class. Glass and steel construction have become the symbol of development in many countries, where people tend to see these buildings as symbols of affluence and luxury.
production of glass
Production of glass:
Making glass is a very ancient process, with archaeological evidence of glass making dating back to before 2500 BC. Once a rare and prized art, manufacturing glass has become a common industry thanks to the Pilkington process.
Traditionally glass was made by blowing liquid glass derived by melting sand calcium oxide and sodium carbonate to extremely high temperatures and the cooling the liquid to the desired shape. Since a few thousand years the recipe to make glass has been the same. It’s just that its properties can be enhanced by adding certain admixtures to the raw materials or by providing suitable coating to meet different needs.
Pilkington process:
Large quantities of raw materials (clear sand, calcium oxide and sodium carbonate)are brought to the glass production plant. They are then weighed and mixed in the right proportion. Certain admixtures are added to the batch to give the glass appropriate proprieties or color.
The mixture is then heated in a gas fired furnace or electric smelter, pot furnace or kiln. Quartz sand without additives becomes glass at a temperature of 2,300 degrees Celsius Adding sodium carbonate (soda) reduces the temperature needed to make glass to 1,500 degrees Celsius.
A homogeneous mixture of molten glass is then formed. This mixture is then floated on molten tin to form glass of desired thickness. After the hot end of the process is over, the glass is set to cool. The way in which the glass is cooled determines its strength. It has to be cooled after maintaining a suitable temperature i.e. it has to be annealed. If it cooled over an extremely short duration of time the glass can become too brittle to handle. Annealing glass is critical to its durability
Glass making is an energy extensive process. One tonne of glass production requires 4 gigajoules of energy. That is as much energy as a wind mill produces in a day! This much energy can also be used to light over 200 homes. (Albeit they are not constructed with glass)
Making glass is a very ancient process, with archaeological evidence of glass making dating back to before 2500 BC. Once a rare and prized art, manufacturing glass has become a common industry thanks to the Pilkington process.
Traditionally glass was made by blowing liquid glass derived by melting sand calcium oxide and sodium carbonate to extremely high temperatures and the cooling the liquid to the desired shape. Since a few thousand years the recipe to make glass has been the same. It’s just that its properties can be enhanced by adding certain admixtures to the raw materials or by providing suitable coating to meet different needs.
Pilkington process:
Large quantities of raw materials (clear sand, calcium oxide and sodium carbonate)are brought to the glass production plant. They are then weighed and mixed in the right proportion. Certain admixtures are added to the batch to give the glass appropriate proprieties or color.
The mixture is then heated in a gas fired furnace or electric smelter, pot furnace or kiln. Quartz sand without additives becomes glass at a temperature of 2,300 degrees Celsius Adding sodium carbonate (soda) reduces the temperature needed to make glass to 1,500 degrees Celsius.
A homogeneous mixture of molten glass is then formed. This mixture is then floated on molten tin to form glass of desired thickness. After the hot end of the process is over, the glass is set to cool. The way in which the glass is cooled determines its strength. It has to be cooled after maintaining a suitable temperature i.e. it has to be annealed. If it cooled over an extremely short duration of time the glass can become too brittle to handle. Annealing glass is critical to its durability
Glass making is an energy extensive process. One tonne of glass production requires 4 gigajoules of energy. That is as much energy as a wind mill produces in a day! This much energy can also be used to light over 200 homes. (Albeit they are not constructed with glass)
properties of glass
Transparency: This property allows visual connection with the outside world. Its transparency can be permanently altered by adding admixtures to the initial batch mix. By the advent of technology clear glass panels used in buildings can be made opaque. (Electro chromatic glazing)
U value: The U-value is the measure of how much heat is transferred through the window. The lower the U-value the better the insulation properties of the glass– the better it is at keeping the heat or cold out.
Strength: Glass is a brittle material but with the advent of science and technology, certain laminates and admixtures can increase its modulus of rupture( ability to resist deformation under load).
Greenhouse effect: The greenhouse effect refers to circumstances where the short wavelengths of visible light from the sun pass through glass and are absorbed, but the longer infrared re-radiation from the heated objects are unable to pass through the glass. This trapping leads to more heating and a higher resultant temperature.
Workability: It is capable of being worked in many ways. It can be blown, drawn or pressed. It is possible to obtain glass with diversified properties- clear, colorless, diffused and stained. Glass can also bewelded by fusion.
Recyclable: Glass is 100% recyclable, cullets (Scraps of broken or waste glass gathered for re-melting) are used as raw materials in glass manufacture, as aggregates in concrete construction etc.
Solar heat gain coefficient: It is the fraction of incident solar radiation that actually enters a building through the entire window assembly as heat gain.
Visible transmittance: Visible transmittance is the fraction of visible light that comes through the glass.
Energy efficiency and acoustic control: Energy-efficient glazing is the term used to describe the double glazing or triple glazing use in modern windows in homes. Unlike the original single glazing or old double glazing, energy-efficient glazing incorporates coated (low-emissivity) glass to prevent heat escaping through the windows. The air barrier also enhances acoustic control.
U value: The U-value is the measure of how much heat is transferred through the window. The lower the U-value the better the insulation properties of the glass– the better it is at keeping the heat or cold out.
Strength: Glass is a brittle material but with the advent of science and technology, certain laminates and admixtures can increase its modulus of rupture( ability to resist deformation under load).
Greenhouse effect: The greenhouse effect refers to circumstances where the short wavelengths of visible light from the sun pass through glass and are absorbed, but the longer infrared re-radiation from the heated objects are unable to pass through the glass. This trapping leads to more heating and a higher resultant temperature.
Workability: It is capable of being worked in many ways. It can be blown, drawn or pressed. It is possible to obtain glass with diversified properties- clear, colorless, diffused and stained. Glass can also bewelded by fusion.
Recyclable: Glass is 100% recyclable, cullets (Scraps of broken or waste glass gathered for re-melting) are used as raw materials in glass manufacture, as aggregates in concrete construction etc.
Solar heat gain coefficient: It is the fraction of incident solar radiation that actually enters a building through the entire window assembly as heat gain.
Visible transmittance: Visible transmittance is the fraction of visible light that comes through the glass.
Energy efficiency and acoustic control: Energy-efficient glazing is the term used to describe the double glazing or triple glazing use in modern windows in homes. Unlike the original single glazing or old double glazing, energy-efficient glazing incorporates coated (low-emissivity) glass to prevent heat escaping through the windows. The air barrier also enhances acoustic control.
types of glass
Float Glass: Float glass is also called soda lime glass or clear glass. This is produced by annealing the molten glass and is clear and flat. Its modulus of rupture is 5000-6000 psi. Stronger than Rocky Balboa taking punches from 2000 psi punches man Ivan Drago. It is available in standard thickness ranging from 2mm to 20mm. and has weight range in 6-26kg/m2. It has too much transparency and can cause glare. It is used in making canopies, shop fronts, glass blocks, railing partitions, etc.
Tinted Glass: Certain additions to the glass batch mix can add color to the clear glass without compromising its strength. Iron oxide is added to give glass a green tint; sulphar in different concentrations can make the glass yellow, red or black. Copper sulphate can turn it blue. Etc.
Toughened Glass This type of glass is tempered, may have distortions and low visibility but it breaks into small dice-like pieces at modulus of rupture of 3600 psi. Hence it is used in making fire resistant doors etc. They are available in same weight and thickness range as float glass.
Laminated Glass: This type of glass is made by sandwiching glass panels within a protective layer. It is heavier than normal glass and may cause optical distortions as well. It is tough and protects from UV radiation (99%) and insulates sound by 50%. Used in glass facades, aquariums, bridges, staircases, floor slabs, etc.
Shatterproof glass: By adding a polyvinyl butyral layer, shatter proof glass is made. This type of glass does not from sharp edged pieces even when broken. Used in skylight, window, flooring, etc
Extra clean glass: This type of glass is hydrophilic i.e. The water moves over them without leaving any marks and photocatylitic i.e. they are covered with Nanoparticles that attack and break dirt making it easier to clean and maintain.
Double Glazed Units: These are made by providing air gap between two glass panes in order to reduce the heat loss and gain. Normal glass can cause immense amount of heat gain and upto 30%of loss of heat of air conditioningenergy. Green, energy efficient glass can reduce this impact.
Chromatic glass: This type of glass can control daylight and transparency effectively. These glass are available in three forms- photochromatic (light sensitive lamination on glass), thermochromatic (heat sensitive lamination on glass) and electrochromatic (light sensitive glass the transparency of which can be controlled by electricity switch.) It can be used in meeting rooms and ICUs
Glass wool: Glass wool is a thermal insulation that consists of intertwined and flexible glass fibers, which causes it to "package" air, and consequently make good insulating materials. Glass wool can be used as filler or insulators in buildings, also for soundproofing.
Glass blocks: Hollow glass wall blocks are manufactured as two separate halves and, while the glass is still molten, the two pieces are pressed together and annealed. The resulting glass blocks will have a partial vacuum at the hollow center. Glass bricks provide visual obscuration while admitting light
Tinted Glass: Certain additions to the glass batch mix can add color to the clear glass without compromising its strength. Iron oxide is added to give glass a green tint; sulphar in different concentrations can make the glass yellow, red or black. Copper sulphate can turn it blue. Etc.
Toughened Glass This type of glass is tempered, may have distortions and low visibility but it breaks into small dice-like pieces at modulus of rupture of 3600 psi. Hence it is used in making fire resistant doors etc. They are available in same weight and thickness range as float glass.
Laminated Glass: This type of glass is made by sandwiching glass panels within a protective layer. It is heavier than normal glass and may cause optical distortions as well. It is tough and protects from UV radiation (99%) and insulates sound by 50%. Used in glass facades, aquariums, bridges, staircases, floor slabs, etc.
Shatterproof glass: By adding a polyvinyl butyral layer, shatter proof glass is made. This type of glass does not from sharp edged pieces even when broken. Used in skylight, window, flooring, etc
Extra clean glass: This type of glass is hydrophilic i.e. The water moves over them without leaving any marks and photocatylitic i.e. they are covered with Nanoparticles that attack and break dirt making it easier to clean and maintain.
Double Glazed Units: These are made by providing air gap between two glass panes in order to reduce the heat loss and gain. Normal glass can cause immense amount of heat gain and upto 30%of loss of heat of air conditioningenergy. Green, energy efficient glass can reduce this impact.
Chromatic glass: This type of glass can control daylight and transparency effectively. These glass are available in three forms- photochromatic (light sensitive lamination on glass), thermochromatic (heat sensitive lamination on glass) and electrochromatic (light sensitive glass the transparency of which can be controlled by electricity switch.) It can be used in meeting rooms and ICUs
Glass wool: Glass wool is a thermal insulation that consists of intertwined and flexible glass fibers, which causes it to "package" air, and consequently make good insulating materials. Glass wool can be used as filler or insulators in buildings, also for soundproofing.
Glass blocks: Hollow glass wall blocks are manufactured as two separate halves and, while the glass is still molten, the two pieces are pressed together and annealed. The resulting glass blocks will have a partial vacuum at the hollow center. Glass bricks provide visual obscuration while admitting light
properties of glass
Polycarbonate: This elastic is 300 times stronger than glass, is resistant to most chemicals, is twice as lighter than class, has high abrasion and impact resistance. It can transmit as much light as glass without many distortions. Applications include window, green house glazing etc.
Acrylic: Acrylic is made of thermo plasticsis weather resistant, is 5 times stronger than glass but is prone to scratches. It has excellent optics, is softer than glass but can accumulate a lot of dust. This is extensively used in to make playhouses, green house etc.
GRP panels: GRP is manufactured by combining hundreds of glass strands together using a pigmented thermosetting UV resin.Glass-reinforced plastics are also used to produce house building components such as roofing laminate, canopies etc. The material is light and easy to handle. It is used in the construction of composite housing and insulation to reduce heat loss.
ETFE: Ethylene tetrafluoroethylene is a plastic with high strength and corrosion resistance. It has high energy radiation resistance properties, it is strong, self cleaning and recyclable.
The versatility of glass keeps on increasing as scientists find new applications to this wonder material. Glass is now being used in the building industry as insulation material, structural component, external glazing material, cladding material; it is used to make delicate looking fenestrations on facades as well as conventional windows. With the advent of green technology in construction, glass is constantly undergoing transformation. Solar power glass, switchable glass projection screens are a few of the newer uses. This is one material to look out for!
Acrylic: Acrylic is made of thermo plasticsis weather resistant, is 5 times stronger than glass but is prone to scratches. It has excellent optics, is softer than glass but can accumulate a lot of dust. This is extensively used in to make playhouses, green house etc.
GRP panels: GRP is manufactured by combining hundreds of glass strands together using a pigmented thermosetting UV resin.Glass-reinforced plastics are also used to produce house building components such as roofing laminate, canopies etc. The material is light and easy to handle. It is used in the construction of composite housing and insulation to reduce heat loss.
ETFE: Ethylene tetrafluoroethylene is a plastic with high strength and corrosion resistance. It has high energy radiation resistance properties, it is strong, self cleaning and recyclable.
The versatility of glass keeps on increasing as scientists find new applications to this wonder material. Glass is now being used in the building industry as insulation material, structural component, external glazing material, cladding material; it is used to make delicate looking fenestrations on facades as well as conventional windows. With the advent of green technology in construction, glass is constantly undergoing transformation. Solar power glass, switchable glass projection screens are a few of the newer uses. This is one material to look out for!
WOOD / TIMBER / LUMBER AS A CONSTRUCTION MATERIAL
Wood has been used as a building material for thousands of years, being second only to stone in terms of its rich and storied history in the world of construction. The chemical properties of wood are inherently complex, but even in spite of this challenge, human beings have successfully harnessed the unique characteristics of wood to build a seemingly unlimited variety of structures. This exceptionally versatile material is commonly used to build houses, shelters and boats, but it is also extensively used in the furniture and home decor industry as well.
Perhaps one of the biggest advantages of using wood as a building material is that it is a natural resource, making it readily available and economically feasible. It is remarkably strong in relation to its weight, and it provides good insulation from the cold. Wood is highly machinable, and can be fabricated into all kinds of shapes and sizes to fit practically any construction need. Wood is also the perfect example of an environmentally sustainable product; it is biodegradable and renewable, and carries the lowest carbon footprint of any comparable building material. In addition, no high-energy fossil fuels are required to produce wood, unlike other common building materials such as brick, steel or plastic. |
LUMBER OR TIMBER?
The words "lumber" and "timber" are often used interchangeably to refer to wood used in construction work, but there has been considerable debate as to which term should apply in a given scenario. Pieces of wood that are smaller than 5 inches wide by 5 inches thick (regardless of length) are generally referred to as lumber. These pieces are machine-planed and sawn to fit certain dimensional specifications (e.g., 2x4", 2x8", etc.) and are primarily used in residential construction. Pieces of wood over 5 inches wide by 5 inches thick (regardless of length) are referred to as timber, and any timber pieces that exceed 8" wide by 8" thick are referred to as beams. As timber pieces are larger in dimension, they are often used to construct the frames of large structures such as buildings and bridges. Timber is also commonly utilized in large quantities for railroad ties, mine shaft supports and crossbeams on utility poles.
Another type of wood commonly used in construction is known as engineered wood. As its name implies, engineered wood is the product of a more intricate fabrication process in which various wood strands, fibers, veneers, or other forms of wood are glued together to form a type of composite material that is used for specific construction applications. Common examples of engineered wood include plywood, glued laminated timber (a.k.a. "glulam"), oriented strand board, fiberboard, and particle board. Engineered wood products are commonly used in a wide variety of residential, commercial and industrial construction projects.
Another type of wood commonly used in construction is known as engineered wood. As its name implies, engineered wood is the product of a more intricate fabrication process in which various wood strands, fibers, veneers, or other forms of wood are glued together to form a type of composite material that is used for specific construction applications. Common examples of engineered wood include plywood, glued laminated timber (a.k.a. "glulam"), oriented strand board, fiberboard, and particle board. Engineered wood products are commonly used in a wide variety of residential, commercial and industrial construction projects.
types of WOOD
Wood has traditionally been classified into two primary categories: Hardwood (any leaf-bearing tree) and softwood (any cone-bearing tree). As with most other general classifications, this can get somewhat confusing due to the fact that there are some leaf-bearing trees that can have relatively soft wood, while some coniferous trees that can have rather hard wood. Generally speaking, however, hardwoods are by and large considered to be heavier and more dense than softwoods. Hardwoods are commonly used in the construction of walls, ceilings and floors, while softwoods are often used to make doors, furniture and window frames. Some examples of the most popularhardwoods include oak, maple, mahogany, cherry, walnut, and teak. Commonly used softwoods include pine, hickory, beach, ash, birch, and cedar.
LUMBER GRADES
The National Hardwood Lumber Association (NHLA) of America has created a grading system to rate various types of lumber, primarily based on the amount of defects that can be found in a board. Below is a brief summary of NHLA grades for both hardwood and softwood lumber.
Hardwoods
1. First and Seconds (FAS) - This is the highest grade possible for hardwood lumber, and is mainly suited for high-quality furnishings, solid wood mouldings and interior joinery. Contains 83% usable material on one face (minimum 6" x 8" board size).
2. Select (Sel) - Also contains 83% usable material, but for a smaller minimum board size (4" x 6") than FAS.
3. #1 Common (#1 Com) - Contains 66% usable material on a 3" x 4" board face.
4. #2 Common (#2 Com) - Contains 50% usable material on a 3" x 4" board face.
Softwoods
1. C Select - Almost completely free of all defects; commonly used for cabinets and interior trim
2. D Select - Comparable to C Select, but may contain small knots (no bigger than the size of a dime)
3. 1 Common - Contains small, tight knots that won't fall out; offers a high-quality knotty appearance (e.g., pine)
4. 2 Common - Very similar to 1 Common, but with slightly larger knots; often used in shelving and paneling
5. 3 Common - Larger knots that what are found in 2 Common; typically used for crates, boxes and fences
Hardwoods
1. First and Seconds (FAS) - This is the highest grade possible for hardwood lumber, and is mainly suited for high-quality furnishings, solid wood mouldings and interior joinery. Contains 83% usable material on one face (minimum 6" x 8" board size).
2. Select (Sel) - Also contains 83% usable material, but for a smaller minimum board size (4" x 6") than FAS.
3. #1 Common (#1 Com) - Contains 66% usable material on a 3" x 4" board face.
4. #2 Common (#2 Com) - Contains 50% usable material on a 3" x 4" board face.
Softwoods
1. C Select - Almost completely free of all defects; commonly used for cabinets and interior trim
2. D Select - Comparable to C Select, but may contain small knots (no bigger than the size of a dime)
3. 1 Common - Contains small, tight knots that won't fall out; offers a high-quality knotty appearance (e.g., pine)
4. 2 Common - Very similar to 1 Common, but with slightly larger knots; often used in shelving and paneling
5. 3 Common - Larger knots that what are found in 2 Common; typically used for crates, boxes and fences
BENEFITS OF WOOD IN CONSTRUCTION
Wood carries several benefits that make it an excellent candidate for use in a wide array of construction projects. One such benefit is its thermal properties, which give it an advantage in terms of its resistance to high temperatures. Unlike steel, which can expand or even collapse in high heat, wood actually dries out and becomes stronger as the heat increases. In addition, the heat conductivity of wood is relatively low in comparison to other materials such as aluminum, marble, steel, or glass. This gives wood an advantage in terms of being used in various applications such as matches, hardware equipment handles, wall coverings, and ceilings.
Wood also contains highly-sought-after acoustic properties. It can absorb sound and echoes, and is a favorite material of choice for the construction of structures where proper acoustics is important, such as concert halls. Wood is resistant to electrical currents, making it an optimal material for electrical insulation. Another important characteristic of wood is its tensile strength, which is its ability to bend under pressure without breaking. Wood is exceptionally light in proportion to its tensile strength, making it the preferred construction choice for surfaces that take a constant beating such as basketball courts and bowling lanes. Tensile strength is also one of the main reasons for choosing timber as a building material; its remarkably strong qualities make it the perfect choice for heavy-duty building materials such as structural beams.
Of the many construction materials that a person can choose from, wood stands out as a unique and amazingly versatile product. Its aesthetic appeal, tensile strength, insulation qualities, and ease of fabrication enable it to remain a favorite choice for use in an extensive array of construction applications.
Wood also contains highly-sought-after acoustic properties. It can absorb sound and echoes, and is a favorite material of choice for the construction of structures where proper acoustics is important, such as concert halls. Wood is resistant to electrical currents, making it an optimal material for electrical insulation. Another important characteristic of wood is its tensile strength, which is its ability to bend under pressure without breaking. Wood is exceptionally light in proportion to its tensile strength, making it the preferred construction choice for surfaces that take a constant beating such as basketball courts and bowling lanes. Tensile strength is also one of the main reasons for choosing timber as a building material; its remarkably strong qualities make it the perfect choice for heavy-duty building materials such as structural beams.
Of the many construction materials that a person can choose from, wood stands out as a unique and amazingly versatile product. Its aesthetic appeal, tensile strength, insulation qualities, and ease of fabrication enable it to remain a favorite choice for use in an extensive array of construction applications.
PLYWOOD AS A CONSTRUCTION MATERIAL
Plywood as a building material is very widely used due to its many useful properties. It is an economical, factory-produced sheet of wood with precise dimensions that does not warp or crack with changes in atmospheric moisture.
Ply is an engineered wood product made from three or more 'plies' or thin sheets of wood. These are glued together to form a thicker, flat sheet. The logs used to make plywood as a building material are prepared by steaming or dipping in hot water. They are then fed into a lathe machine, which peels the log into thin plies of wood. each ply is usually between 1 and 4mm thick. Uses of plywood as a building material
Plywood has a huge range of used within the construction industry. Some of its most common uses are:
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HOW PLY IS MADE
Plywood consists of the face, core, and back. The face is the surface that is visible after installation, while the core lies between the face and back. Thin layers of wood veneers are glued together with a strong adhesive. This is mainly a phenol or urea formaldehyde resin. Each layer is oriented with its grain perpendicular to the adjacent layer. Plywood as a building material is generally formed into large sheets. It may also be curved for use in ceilings, aircraft, or ship building.
which wood is ply made of?
Plywood is manufactured fromsoftwood, hardwood, or both. The hardwoods used are ash, maple, oak, and mahogany.Douglas fir is the most popular softwood for making plywood, although pine, redwood, and cedar are common. Composite plywood can also be engineered with a core of solid timber pieces or particleboard, with a wood veneer for the face and back. Composite plywood is preferable when thick sheets are required.
Additional materials can be added to the face and back veneers to improve durability. These include plastic, resin-impregnated paper, fabric, Formica, or even metal. These are added as a thin outer layer to resist moisture, abrasion and corrosion. They also facilitate better binding of paint and dyes.
Additional materials can be added to the face and back veneers to improve durability. These include plastic, resin-impregnated paper, fabric, Formica, or even metal. These are added as a thin outer layer to resist moisture, abrasion and corrosion. They also facilitate better binding of paint and dyes.
PROPERTIES
High Strength: Plywood has the structural strength of the wood it is made from. This is in addition to the properties obtained from its laminated design. The grains of each veneer are laid at 90 degree angles to each other. This makes the whole sheet resistant to splitting, especially when nailed at the edges. It also gives the whole sheet uniform strength for increased stability. Furthermore, plywood has a higher strength to weight ratio as compared to cut lumber. This makes it ideal for flooring, webbed beams, and shear walls.
High panel shear: Plywood is made with an odd number of layers, making it tough to bend. The angle at which the veneer grains are laid against each other may be varied from 90 degrees. Each veneer can be laid at a 45 or 30 degree angle to the next one, increasing the plywood’s strength in every direction. This cross lamination increases the panel shear of plywood, important in bracing panels and fabricated beams.
Flexibility: Unlike cut timber, plywood can be manufactured to fit every requirement. The thickness of each veneer can vary from a few millimeters to several inches. The number of veneers used also ranges from three to several, increasing the thickness of the sheet. The extra layers add more strength to the plywood. Thinner veneers are used to increase flexibility for use in ceilings and paneling.
Moisture resistance: The type of adhesive used to bind the veneers makes the plywood resistant to moisture and humidity. A layer of paint or varnish can also increase resistance to water damage. These types of veneers are suitable for exterior use such as cladding, sheds, and in marine construction. They are also suited for holding concrete while it sets. Moisture resistance is important in interior applications as well, including on floors. The cross lamination ensures the veneers do not warp, shrink, or expand when exposed to water and extreme temperature.
Chemical resistance: Plywood treated with preservative does not corrode when exposed to chemicals. This makes it suitable for chemical works and cooling towers.
Impact resistance: Plywood has high tensile strength, derived from the cross lamination of panels. This distributes force over a larger area, reducing tensile stress. Plywood is therefore able to withstand overloading by up to twice its designated load. This is critical during short-term seismic activity or high winds. It is also useful in flooring and concrete formwork.
Fire resistance: Plywood can be treated with a fire resistant chemical coating. More commonly, it is combined with non combustible materials such as plasterboard or fibrous cement. This makes it ideal for use in fire resistant structures.
Insulation: Plywood has high thermal and sound insulation. This makes it a useful insulating material for flooring, ceilings, roofing, and wall cladding. Insulation offered by plywood can greatly reduce heating and cooling costs.
High panel shear: Plywood is made with an odd number of layers, making it tough to bend. The angle at which the veneer grains are laid against each other may be varied from 90 degrees. Each veneer can be laid at a 45 or 30 degree angle to the next one, increasing the plywood’s strength in every direction. This cross lamination increases the panel shear of plywood, important in bracing panels and fabricated beams.
Flexibility: Unlike cut timber, plywood can be manufactured to fit every requirement. The thickness of each veneer can vary from a few millimeters to several inches. The number of veneers used also ranges from three to several, increasing the thickness of the sheet. The extra layers add more strength to the plywood. Thinner veneers are used to increase flexibility for use in ceilings and paneling.
Moisture resistance: The type of adhesive used to bind the veneers makes the plywood resistant to moisture and humidity. A layer of paint or varnish can also increase resistance to water damage. These types of veneers are suitable for exterior use such as cladding, sheds, and in marine construction. They are also suited for holding concrete while it sets. Moisture resistance is important in interior applications as well, including on floors. The cross lamination ensures the veneers do not warp, shrink, or expand when exposed to water and extreme temperature.
Chemical resistance: Plywood treated with preservative does not corrode when exposed to chemicals. This makes it suitable for chemical works and cooling towers.
Impact resistance: Plywood has high tensile strength, derived from the cross lamination of panels. This distributes force over a larger area, reducing tensile stress. Plywood is therefore able to withstand overloading by up to twice its designated load. This is critical during short-term seismic activity or high winds. It is also useful in flooring and concrete formwork.
Fire resistance: Plywood can be treated with a fire resistant chemical coating. More commonly, it is combined with non combustible materials such as plasterboard or fibrous cement. This makes it ideal for use in fire resistant structures.
Insulation: Plywood has high thermal and sound insulation. This makes it a useful insulating material for flooring, ceilings, roofing, and wall cladding. Insulation offered by plywood can greatly reduce heating and cooling costs.
TYPES OF PLYWOOD
Structural plywood: Used in permanent structures where high strength is needed. This includes flooring, beams, formwork, and bracing panels. It can be made from softwood or hardwood.
External plywood: Used on exterior surfaces where a decorative or aesthetic finish is important. It is not used to bear loads or stress, such as on exterior door surfaces, and wall cladding.
Internal plywood: This has a beautiful finish, for non-structural applications like wall paneling, ceilings, and furniture.
Marine plywood: It is specially treated using preservatives, paint, or varnish, to resist water damage. It is used in shipbuilding, resists fungal attacks and does not delaminate.
External plywood: Used on exterior surfaces where a decorative or aesthetic finish is important. It is not used to bear loads or stress, such as on exterior door surfaces, and wall cladding.
Internal plywood: This has a beautiful finish, for non-structural applications like wall paneling, ceilings, and furniture.
Marine plywood: It is specially treated using preservatives, paint, or varnish, to resist water damage. It is used in shipbuilding, resists fungal attacks and does not delaminate.
GRADES OF PLYWOOD
Plywood grades are determined by strength, discolorations, surface defects, and resistance to moisture, among other properties. The quality of surface veneer, type of wood, and strength of adhesive, will then be allocated a particular rating. Each rating will determine the type of application the plywood is suited for.
Plywood grades are N, A, B. C, and D. The D grade has several surface defects such as graining and knotting, while the N grade has few of these. An “interior C-D” rating for example, indicates the plywood has a grade C face, and a grade D back. It also means the adhesive is suited for interior applications.
The unique characteristics of plywood, its cost effectiveness, and ease of use will continue to popularize plywood as a building material.
Plywood grades are N, A, B. C, and D. The D grade has several surface defects such as graining and knotting, while the N grade has few of these. An “interior C-D” rating for example, indicates the plywood has a grade C face, and a grade D back. It also means the adhesive is suited for interior applications.
The unique characteristics of plywood, its cost effectiveness, and ease of use will continue to popularize plywood as a building material.
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