Master builder. Strength in stone
Stonehenge, England was begun nearly 5.000, years ago. The builders
had no machines, or even wheels lo help them. They Had to drag huge
blocks of stone, each weighing as much as 13 hippos, from 40km (25-
miles) away. The total hours worked by the builders of Stonehenge adds up to 30 million hours.
Canal fever
The Panama Canal, which links the Pacific and Atlantic Oceans, was built, between 1904-1014. To build the 82km (51 mile) long canal. 43,000 men dug up enough soil to cover over 14.000 soccer fields. Many workers died from yellow fever and malaria and two whole years were spent clearing the swamps where disease-carrying mosquitoes bred.
Marble marvel
The Taj Mahal in India look 20.000 labourers 20 years to complete. It is made of while marble inlaid with precious stones. The Taj was built by Emperor Shah jahan as a lomb lor his wife. On its completion, the emperor had the architect's head cut off to stop him designing a more beautiful building.
Roads for Romans
The Romans began building roads across their empire in about 312BC By AD200 they had built about 85,000 km (53.000 miles) of roads, enough to run twice around the world. The roads were so well built that some have lasted for over 2 000 years. Most modern roads last for less than 50 years.
Channel tunnel
In December 1990 French and British miners became the first people to walk between the two countries since the Ice Age, 19.000 years ago when the Channel was dry land. To bore the Channel Tunnel deep under the sea between Britain and France, enough chalky soil was dug up to make a medium-sized town.
Volcano challenge
The 11 century chapel of Saint-Michel-d'Aiguilhe stands on an ancient extinct volcano near Le Puy France. Its builders had to haul their material and tools up to the top of the 79m (260ft) high cone in baskets.
Up, up in the air
Many of the steel frames for skyscrapers in the USA are put up by Mohawk Indians from Montreal, Canada. They walk across beams just wider than your foot, over 244m (800 ft) above ground.
At a gallop
The Tacoma Narrows Bridge in the USA was one of the worst ever engineering feats. In high winds, its deck swung up and down in giant waves. The bridge was intended to withstand winds of 190kph (120mph). Four months alter it opened, though, it collapsed in winds of 67kph (42mph).
Unit 2
Building materials
I. Memorize the following words and expressions:
cob -
cob wall -
sod - ,
attribute ,
loose granite rocks
to strp a bark - ( )
kiln ,
(, ..)
II. Read the text:
Building materials
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Building material is any material which is used for a construction purpose. Just about every type of available material has been used at one time or another for creating various human and animal homes, structures, and technologies.
Living spaces and their related structures have been created using different materials, from mud to metal, and from plastic to grass. The list of building materials is quite long.
Mud, stone, and brush are probably the most basic building materials. People all over the world have used these materials to create homes to suit their local weather conditions. In general stone and brush are used as basic structural components in buildings, while mud is used to fill in the space between acting as a type of concrete and insulation. The amount of each material used leads to different styles of buildings. Building with mostly dirt and clay such as cob and sod, resulted in homes that have been built for centuries in western and northern Europe as well as the rest of the world. Some of these buildings have remained habitable for hundreds of years.
Rock structures have existed for as long as history can recall. It is the longest lasting building material available, and is usually readily available. There are many types of rock with different attributes that make them better or worse for particular uses. Rock is a very dense material so it gives a lot of protection too, its main drawback as a material is its weight.
The granite-strewn uplands of Dartmoor National Park, United Kingdom, for example, provided ample resources for early settlers. Circular huts were constructed from loose granite rocks throughout the Neolithic and early Bronze Age. Granite continued to be used throughout the Medieval period and into modern times. Stone buildings can be seen in most major cities, some civilisations built entirely with stone such as the Pyramids in Egypt, the Aztec pyramids and the remains of the Inca civilisation.
Wood is a product of trees used for construction purposes when cut into lumber and timber, such as boards, planks and similar materials. It is a generic building material and is used in building just about any type of structure in most climates. Wood can be very flexible under loads, keeping strength while bending, and is incredibly strong when compressed vertically. Historically, wood for building large structures was used in its unprocessed form as logs. The trees were just cut to the needed length, sometimes stripped of bark, and then notched or lashed into place.
Houses can also be built of brick. A brick is a block made of kiln-fired material, usually clay or shale, but also may be of mud, etc. Clay bricks are formed in a moulding (the soft mud method), or in commercial manufacture more frequently by extruding clay through a die and then wire-cutting them to the proper size (the stiff mud process).
Concrete is a composite building material made from a combination of aggregate (composite) and a binder such as cement. The most common form of concrete is portland cement concrete, which consists of mineral aggregate (generally gravel and sand), portland cement and water. After mixing, the cement hydrates and eventually hardens into a stone-like material. When used in the generic sense, this is the material referred to by the term concrete.
For a concrete construction of any size, as concrete has a rather low tensile strength, it is generally strengthened using steel rods or bars (known as rebars). This strengthened concrete is then referred to as reinforced concrete. In order to minimise any air bubbles (that would weaken the structure), a vibrator is used to eliminate any air that has been entrained when the liquid concrete mix is poured around the ironwork.
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Metal is used as structural framework for larger buildings such as skyscrapers, or as an external surface covering. Steel is a metal alloy whose major component is iron, and is the usual choice for metal structural building materials. The lower density and better corrosion resistance of aluminium alloys sometimes overcome their greater cost.
The term plastics covers a range of synthetic or semi-synthetic organic condensation or polymerization products that can be molded or extruded into objects or films or fibers. Their name is derived from the fact that in their semi-liquid state they have the property of plasticity. Plastics vary immensely in heat tolerance, hardness, and resiliency. Combined with this adaptability, the general uniformity of composition and lightness of plastics ensures their use in almost all industrial applications today.
III. Now say which material:
1. is made from a combination of aggregate and binder? (cement)
2. was historically used for building in its unprocessed form? (wood)
3. can be made in the course of the stiff mud process? (brick)
4. was used to build the Aztec pyramids? (rock)
IV. Answer the questions:
1. What are basic building materials?
2. Do you think the list of building materials used for costruction today is complete? If not, what
other materials would you add to the list?
3. How would you describe the properties of the most widely used building materials?
4. What building materials do you think will be used in 100 years' time?
V. Match building materials to their descriptions:
| A | B | ||
| concrete | A | hard vulcanized rubber | |
| Portland cement | B | powder made from alumina, silica, lime, iron oxide, and magnesia burned together in a kiln and finely pulverized | |
| vulcanite | C | gray, brown or black quartz | |
| marble | D | a hard strong building material made by mixing a cementing material (commonly Portland cement) and a mineral aggregate | |
| flint | E | artificial stone of crushed granite and cement | |
| cement | F | a mixture of limestone and clay, burned in a furnace and then pulverized. Impervious to water, it actually becomes stronger if submerged after it hardens | |
| granolith | G | limestone crystallized in varying degrees by metamorphism ranging from granular to compact in texture, usually white or veined or tinted or mottled |
VI. Now look at this table:
| Density kg/m3 | Melting point 0C | Typical tensile strength N/mm2 | Relative cost | |
| Glass | ||||
| Concrete | - | |||
| Softwood (pine) Hardwood (oak) | 5500 8800 | - - | 40 100 | |
| Mild steel | ||||
| Aluminium | ||||
| Copper Zinc | 8950 7100 | 1083 420 | 340 110 | 25 20 |
a) Identify these materials from the table:
a) This material has a slightly lower density than aluminium.
b) This material has a much higher melting point than glass.
c) This material has a tensile strength much higher than concrete, but slightly lower than
zinc.
d) This material is slightly lighter than oak but is much stronger in tension.
e) This material has a considerably higher melting point than copperr but a much
lower tensile strength.
f) This material has a tensile strength approximately twice that of pine.
g) The melting point of this material is approximately 1 1/2 times as high as that of copper.
h) The density of this material is approximately half that of pine.
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i) This material is ten times as strong as concrete in tension.
j) These two materials have very nearly the same tensile strength.
b) In pairs, compare some materials as in the following way:
e.g. Oak is considerably heavier than pine, has a much higher tensile strength and costs 2l/2 times more per kilogramme.
a) glass and concrete
b) aluminium and mild steel
c) copper and zinc
d) pine and mild steel
VII. a) Which materials do you think can be used for different building components? Give your reason.
b) In pairs, use the table below together with the table in Exercise VI to make conversations like the following:
CLIENT: What do you think is the best material to use for the cladding?
ARCHITECT: Well, aluminium isn't really suitable. It's strong enough but it's too expensive. I
think we should use mild steel. It's not only strong enough but it's also cheaper.
| cladding | aluminium mild steel | A tensile strength of mot less than 90 N/mm² |
| beam | pine oak | A tensile strength of not less than 35 N/mm² |
| roof covering | zinc cooper | Weight should not exceed 8000 kg/m³ |
| Fire door | mild steel cooper | Melting point should be in excess of 1000 ºC |
VIII. a) Read the passage about concrete:
Concrete is made from cement, coarse aggregate (stones), fine aggregate (sand or crushed stone) and water. Coarse aggregate ranging from 5 mm to 40 mm may be used for normal work. The maximum size of the aggregate should not be greater than one quarter of the minimum thickness of the finished concrete. The normal maximum sizes are 20 mm and 40 mm (20 mm being more common). The maximum size of aggregate which should be used in small concrete sections, or where reinforcement is close together, is 10 mm.
Reinforced concrete section
In concrete with widely spaced reinforcement, such as solid slabs, the size of the coarse aggregate should not be greater than the minimum cover to the reinforcement otherwise spalling will occur, i.e. the breaking off of pieces of concrete below the reinforcement. For heavily reinforced sections, e.g. the ribs of main beams, the maximum size of the coarse aggregate should be either:
(i) 5 mm less than the minimum horizontal distance between the reinforcing rods, or,
(ii) 5 mm less than the minimum cover to the reinforcement, whichever is the smaller.
