Complete the sentences by filling in the correct word that fits a statement (gap fill). Choose the appropriate words from the word bank given below.

A. exhaust B. requirements C. total D. amount

E. composition F. non-combustible G. additional

H. wonder I. form J. voids K. powder L. fuel

1. A significant …… of energy is generated by burning coal in power plants throughout the world.

2. Another source of fly ash are the boilers from industrial plants that uses pulverized coal or lignite as …… .

3. These particles are collected from the …… before they fly away and are used in making concrete products.

4. These particles come together and solidifyto …… glassy spherical particles which are finer than the cement particles.

5. Fly ash is used in a variety of applications involving structural and low strength ….

6. The amount of fly ash in the Portland cement will vary on the basis of chemical …… of both fly ash and Portland cement.

7. The fine aggregate in the cement should be reduced for the …… volume of fly ash.

8. The fine particlesof fly ash can be used to effectively fill …… .

9. Coal is not completely carbon, it contains quantities of …… minerals.

10. When the coal burns in a power plant, it not only generates energy but also produces a …… kind of material.

UNIT 15

Concrete Mix with Fly Ash

Read, translate the following text and be ready to fulfil the tests:

Fly ash or pulverized fuel ash (pfa) is a finely divided powder thrown out as a waste material at the thermal power plants using pulverized coal for raising steam in the boilers. The fly ash is an industrial waste and great hazard for our environment. In the building industry, the use of fly ash as a part replacement of cement in mortar and concrete at the construction site has been made all over the world and is well known.

The important building materials which can be produced from fly ash are:

- Portland fly ash cement.

- Ready-mixed fly ash concrete.

- Precast fly ash concrete building units.

- Sintered fly ash lightweight aggregate for concrete.

- Lime fly ash cellular concrete.

- Fly ash building bricks.

- Fly ash stabilized high-magnesia cement.

- Oil-well cementing composition.

- Hydraulic binders.

- Bituminous products.

The advantages of fly ash concrete over the corresponding plain cement concrete are:

- Improved workability.

- Lower heat of hydration.

- The increase in creep with fly ash content up to 15% is negligible.

- Increases the modulus of elasticity of concrete when concretes of the same strength with and without fly ash are compared.

- Superior resistance to freezing and thawing.

- Improved sulphate resistance.

- Lower water and air permeability.

- Lower leaching of lime liberated during hydrating of cement.

- Reduced alkali-aggregate reactions.

- Greater resistance to attack of aggressive waters.

Since a huge quantity of cement is used in mass concrete construction and the cost of fly ash is negligible as compared to that of the cement, the use of fly ash concrete brings about a substantial saving in cement consumption and overall construction cost. Fly ash concrete may be used in concrete structures including high strength concrete without any risk of steel corrosion. Researchers have proved that concrete with approved quality fly ash does not induce corrosion of reinforcing steel even in marine and industrial aggressive environments. With proper mix design the 7 and 28-days strength of fly ash concrete may be equal or even more than plain concrete. The 90 days strength of fly ash concrete may be more than 140% of plain concrete.

Read, listen to the pronunciation and memorize the active vocabulary to the text:

Active Vocabulary

1. powder порошок, пыль

2. waste material отходы

3. alkali-aggregate reaction щелочная реактивность заполнителей, реакция заполнителей на воздействие щелочей

4. replacement замена

5. mortar строительный раствор

6. construction site строительная площадка

7. ready-mixed concrete товарная бетонная смесь, бетонная смесь заводского изготовления

8. cellular ячеистый, пористый

9. workability удобоукладываемость (бетонной, растворной смеси), удобообрабатываемость (материала), применимость; годность

10. creep медленное относительное перемещение, сдвиг, наклон

11. negligible незначительный, не принимаемый в расчет

12. thawing оттаивание, размораживание

13. permeability проницаемость, коэффициент фильтрации

14. leaching выщелачивание, продукт выщелачивания

15. substantial прочный, крепкий; существенный

16. consumption потребление, расход, затрата

17. researcher исследователь

18. to induce вызывать, побуждать, индуцировать

19. environment окружающая среда, внешние условия, окружающая обстановка, окружение

20. hazard (потенциальная) опасность, риск, опасный фактор; вредный фактор

21. equal одинаковый, равный

22. plain (здесь) простой, обыкновенный

CONTROL TESTS

TEST I

Decide whether these statements are true or false:

1. a). Fly ash is a finely divided powder classified into two types on the basis of its chemical composition.

b). Fly ash is a finely divided powder produced from burning anthracite or bituminous coal.

c). Fly ash is a finely divided powder thrown out as a waste material at the thermal power plants using pulverized coal.

2. a). Fly ash is an industrial waste that can be used for manufacturing concrete blocks.

b). Fly ash is an industrial waste and great hazard for our environment.

c). Fly ash is an industrial waste and a vital ingredient of all the concrete products.

3. a). The use of fly ash as a part replacementof cement in mortar and concrete at the construction site has been made all over the world.

b). The use of fly ash as a part replacement of cement in mortar and concrete requires less energy for pumping.

c). The use of fly ash as a part replacement of cement in mortar and concrete is widely spread in structural fill applications.

4. a). Fly ash increases the modulus of elasticity of concrete when it contains some quantities of non-combustible minerals.

b). Fly ash increases the modulus of elasticity of concrete when it contains molten particles rich in silica, alumina, and calcium.

c). Fly ash increases the modulus of elasticity of concrete when concretes of the same strength with and without fly ash are compared.

5. a). Researchershave proved that concrete with approved quality fly ash contains a low concentration of lime and a high concentration of silica, aluminum, and iron.

b).Researchers have proved that concrete with approved quality fly ash does not induce corrosion of reinforcing steel even in marine and industrial aggressive environments.

c). Researchers have proved that concrete with approved quality fly ash can be used in places where the concrete may be exposed tosulphate ions in ground and water.

TEST II

Match words in columns A and B (synonym match):

A B

1. to divide a). to cause b). to contribute

c). to view d). to share

2. waste a). refuse b). need

c). taste d). order

3. hazard a). purlin b). danger

c). strut d). truss

4. unit a). angle b). glue

c). block d). joist

5. superior a). higher-level b). harmful

c). eventual d). comprehensive

6. negligible a). agreeable b). special

c). pleasant d). insignificant

7. to compare a). to become b). to match

c). to mix d). to contact

8. permeability a). penetration b). capability

c). possibility d). workability

9. consumption a). resistance b). substance

c). support d). expenditure

10. to approve a). to applaud b). to authorize

c). to suspend d). to attribute

TEST III

Select the best possible answer out of the choices from the list to the statements (multiple choice):

1. The use of fly ash as a part replacement of cement in mortar and concrete …

a. demonstrates improved workability.

b. results in lower heat of hydration.

c. reduces alkali-aggregate reactions.

d. has been made all over the world.

2. Fly ash concrete … .

a. is supposed to be known as a low quality cementitiousmaterial.

b.brings about a substantial saving in cement consumption.

c. shows low sulphate resistance.

d.has increased alkali-aggregate reactions.

3. Researchershave proved that concrete with approved quality fly ash … .

a. does not induce corrosion of reinforcing steel.

b. does not exhibit greater resistance to attack of aggressive waters.

c. does not expose high resistance to freezing and thawing.

d. does not provide lower leaching of lime.

4. The use of fly ash increases … .

a. cement consumption.

b. overall construction cost.

c.the modulus of elasticity of concrete.

d. the heat of hydration.

5. Pulverized fuel ash (pfa) is a finely divided powder … .

a. which increases water and air permeability of a mortar.

b.used in oil-well cementing compositions.

c. thrown out as a waste material at the thermal power plants.

d. which reduces workability of concrete.

TEST IV