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1) Talk about concrete with your partner. Try to guess:
-
In what epoch of history come up with concrete? (prehistory,
antiquity,
middle ages)
-
Name at least 3 ingredients of concrete.
water, cement, sand
-
What you can use to reinforce concrete?
steel
CONCRETE
Concrete is a mixture of portland cement, water, fine and coarse aggregates. This plastic paste,
when placed in forms or molds and cured, combines chemically to create a stonelike product. The Ancient
Romans were well acquainted with concrete. The culmination of their construction skills was the casting
in concrete of magnificent dome of the Pantheon (126 A.D.). Spanning 43 m, it is still in excellent
condition. This span was not exceeded until the twentieth century. Roman concrete was based upon
pozzolana, a natural volcanic dust which, when mixed with slakes lime, produced a slow-setting cement.
The knowledge of concrete manufacture did not survive the Western Empire; it was lost in the Dark Ages.
Modern concrete was discovered by an Englishman, Joseph Asdin, in 1824. He found that a
mixture of limestone and clay, when properly processed, made a cement product resembling limestone
from the quarries of the English Isle of Portland. Asdin was awarded a patent for hydraulic cement, a
cement that would cure under water, which he called portland cement. It is essentially the same product
that is used today.
The potential for increasing the structural capability of a new material was soon recognized.
While strong in compression, concrete is weak in tension. If iron or steel rods, strong in tension, could be
incorporated into the structure in a proper location, they would reinforce the concrete.
Although only one ingredient of concrete, portland cement is the key unifying element. To make
portland cement, a mixture of calcium, silica, alumina and iron is ground to a fine powder. This mixture is
then fed continuously into a rotary kiln where it is heated to above 1,316 degrees Celsius. At this
temperature chemical activity takes place, essentially creating calcium compounds of the metals. After
the resultant clinker is ground to fine powder, a small amount of gypsum is added to control the setting
time. A high level of control is necessary at every step in the process. This is normal portland cement.
Standard portland cement is medium-gray in color. When this is not satisfactory, white (or very
nearly white) cement is available. This is produced by carefully selecting the ingredients for color and
reducing the iron and manganese content. Considering the fact that 80 percent of concrete is composed
of aggregate, using dark aggregate will not produce white, or even light concrete. To produce these, the
aggregates would have to be light in color, such as limestone. If special colors are desired, mineral
pigments can be added to this light concrete.
Gravel and sand are the common designations for coarse and fine aggregates. These are
misnomers because the qualitative aim of sand and gravel is to be composed of particles of uniform size.
For concrete aggregate the opposite is desired. The greatest variety of particle size produces the most
desirable concrete aggregate. If the particles are screened, it is to see that a proper mixture of size is
included.
Since aggregate makes up the bulk of a mass of concrete, care must be taken to use material of
sufficient hardness and strength, clean and free of organic materials. Since cement is the most expensive
ingredient and must fill all void between the aggregate particles, proper grading will generate the most
economical concrete.
Lightweight aggregates have qualities to consider. Normal stone concrete is calculated at about
2,400 kg per cubic meter; lightweight concrete is half that or less. Lightweight concretes may be classifies
as structural, nonstructural or reduced structural. The former are usually expanded shale, the latter
expanded mica. These introduce a good deal of air space into a concrete. In addition to decreasing the
weight of concrete, lightweight aggregate increases the insulation value, which is very low ordinary stone
concrete.
CONCRETE IN CONSRTUCTION
When the optimum water/cement ratio has been attained, and the concrete is placed, care must
be taken to prevent evaporation of the water before complete hydration has taken place. This is what
meant by the term “curing”. There are number of ways to accomplish curing; the choice is largely based
upon site conditions. The simplest method is to delay the stripping of the forms for a minimum of two
weeks. This is particularly effective for columns and deep structural members where little of the concrete
surface is exposed. In the case of slabs and other highly exposed surfaces, or where the forms must be
quickly reused, all exposed surfaces must be kept wet. If below water level, the structure may be flooded.
In most cases, spraying is necessary, sometimes after covering the surface with cloth or straw. More
often, today, the wetted surface is covered with plastic sheeting to retard drying. A recent curing
technique is to paint the freshly exposed surfaces with a latex sealant to slow the process of evaporation.
Steel Reinforcement.
Concrete is used without reinforcement in some applications, such as mass
foundations, where the only forces involved are compressive. In any case where tensile forces are
encountered, steel reinforcement greatly increase the structural capacity of the material.
Reinforcement serves a second function: to handle temperature changes. Aside from steel added
for structural requirements, there is “temperature” steel, which is placed in the concrete to control
expansion, contraction, and the consequent cracking due to temperature changes. The amount of
temperature steel required is constant percentage of the area of concrete.
Tensile reinforcement is laid in the forms following the calculated lines of tensile stress. Shop
drawings are prepared from the structural plans, the bars are cut and bent as required, and they are
delivered to the site ready for placement.
2) Fill the crosswords using words from the text.
1.
T
2.
L I M E S T O
3.
4.
K I
5.
C A L C
6.
A
7.
L I G
8.
R O
9.
W
10.
S A
1.
2.
3.
E
N
G
L
I
S
H
M
A
N
N
E
R
N
U
D
T
A
T
D
S
I O N
A Y
M
I N
N S
E R
Concrete is weak in it and will be better when you use steel.
You can use it like a building material or birder. In Poland it is possible to find it in Tatry mountain.
A color of cement.
4.
To get a powder named portland cement you have to insert mixture of calcium, silica, alumina
and iron there.
5.
In chemistry you know it as a [Ca].
6.
Surname of a man, who discovered a modern concrete.
7.
Opposite to light (about concrete).
8.
They knew qualities of concrete very well.
9.
Liquid ingredient of a concrete.
10. Friable material, ingredient of a concrete. There is a lot of that material on the beach.
3) Point the correct sentences. If the sentence is false write down the correct one.
1.
2.
3.
4.
5.
6.
7.
It is not important to use properly prepared materials to create a concrete. T/F
If you want to change gray color of concrete you can use some special pigments.
T/F
Adjective
coarse
means that material is very soft. T/F
Joseph Asdin discovered modern concrete, because he added limestone to water. T/F
Portland cement is a kind of cement, which grow up in water.
T/F
Concrete is never used without reinforcement. T/F
Steel used as reinforcement performs the function of increasing capacity and handling
temperature changes.
T/F
8. Term “curing” means
evaporation of water from the surface of the concrete. T/F
9. It is good for concrete to stay dry, when used in highly exposed surfaces. T/F
10. Steel has to be carefully prepared according to the plans before placing in the boarding.
T/F
4) Match nouns with their definitions.
1. evaporation
2.
tensile
3. fine
4.
latex sealant
5. rod
6. gravel
7. hydration
8.
capacity
9. mold
10.
compressive
11.
expansion
12. spraying
13. cliner
14. clay
1. f
2. i
3. j
a. a type of heavy sticky earth that can be used for makig pots, bricks etc.
b.
substance causing delay evaporation of water
c. using it you can form concrete in a proper shape
d.
axially directed pushing forces
e.
tendency of matter to change in volume in response to a change in temperature
f.
the process by which water is converted from its liquid form to its vapor form
g. a long thin pole or bar
h.
pouring the outer surface of the concrete with water
i.
stretching or pulling
j. (adj.) when sth has very high quality
k.
reaction with water; portland cement mixed with sand gravel and water produces the
synthetic rock we call concrete
l. small stones, used to make a surface for pths, roads etc.
m.
the ability to carry the load
n. the hard material like rock, which is left after coal has been burnt
4. b
5. g
6. l.
7. k
8. m
9. c
10. d 13. n
11. e 14. a
12. h
ZADANIA DODATKOWE (ZWIĄZANE Z BUDOWNICTWEM)
1.
Match the terms from below with the correct shape.
2.
Connect the roof descriptions with the appropriate drawings.
VOCABULARY:
3.
Match the terms from below with the correct member.

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