what is chemical composition of cement?

what is chemical composition of cement?

""Question 74""

""brief description""

The raw materials used for the manufacture of cement consist mainly of lime, silica, alumina and iron oxide. These oxides interact with one another in the kiln at high temperature to form more complex compounds. The relative proportions of these oxide compositions are responsible for influencing the various properties of cement; in addition to rate of cooling and fineness of grinding.

Approximate Oxide Composition Limits of Ordinary Portland Cement

Oxide Per cent content

CaO 60–67

SiO2 17–25

Al2O3 3.0–8.0

Fe2O3 0.5–6.0

MgO 0.1–4.0

Alkalies ( K2O, Na2O) 0.4–1.3

SO3 1.3–3.0

The identification of the major compounds of cement is largely based on Bogue’s equations and hence it is called “Bogue’s Compounds”. The four compounds usually regarded as major compounds are listed in below.

Major compounds of cement

Name of Compound Formula

Tricalcium silicate 3 CaO.SiO2

Dicalcium silicate 2 CaO.SiO2

Tricalcium aluminate 3 CaO.Al2O3 

Tetracalcium 4CaO.Al2O3.Fe2O3

aluminoferrite

It is to be noted that for simplicity’s sake abbreviated notations are used. C stands for CaO, S stands for SiO2, A for Al2O3, F for Fe2O3 and H for H2O. 

The equations suggested by Bogue for calculating the percentages of major compounds are given below.

C3S = 4.07 (CaO) – 7.60 (SiO2) – 6.72 (Al2O3) – 1.43 (Fe2O3) – 2.85 (SO3)

C2S = 2.87 (SiO2) – 0.754 (3CaO.SiO2)

C3A = 2.65 (Al2O3) – 1.69 (Fe2O3)

C4AF= 3.04 (Fe2O3)

Two International Finance Center, Hong Kong

Two International Finance Center, 

Hong Kong

Height : 415 meters

Cost to build : US$2.5

billion

Completion date: August

2008

Fast facts : In "Lara

Croft Tomb Raider: The

Cradle of Life," Lara

Croft leaped off the

building. In "The Dark

Knight," Batman leaped from 2IFC to IFC. Two

International Financial Center is the definitive

point of Hong Kong’s awe-inspiring skyline and a

symbol of its wealth.

Located in the center of Hong Kong’s financial

district, this shimmering 415-meter obelisk fits every

criterion of a financial powerhouse.

It houses some of the world’s largest financial

institutes, it is situated on 8 Finance Street and

has 88 floors -- the number eight is an auspicious

digit in Hong Kong.

The building is topped with a crown that some liken

to a beard trimmer.

75 CIVIL ENGINEERING INTERVIEW QUESTIONS

75 CIVIL ENGINEERING 

INTERVIEW QUESTIONS:

1. What is bending moment (BM) & Shear force (SF) – Explain.

2. What are the steps involved in the concreting process, explain?

3. Describe briefly the various methods of concrete curing.

4. What is the minimum curing period?

5. What Do You Understand by M25 Concrete?

6. What is Water-Cement Ratio and How it is related to the strength of concrete?

7. What is a bearing capacity of soil?

8. How to increase the bearing capacity of soil?

9. What are the different types of foundation?

10. Explain moment of inertia and its importance.

11. How do we determine the specific gravity of a cement?

12. Density Of 1 cum cement?

13. What are the causes of building collapse?

14. What is bar bending schedule (BBS) & how to prepare it?

15. Why is concrete cube test carried out?

16. Why is concrete slump test carried out?

17. What is bleeding, segregation, honeycombing of concrete?

18. What is pre-stressed concrete? Which reinforcement is used in prestressed concrete?

19. What is the ratio of steel and concrete to use in slabs, beams, columns?

20. Difference between pre-tensioning and post-tensioning?

21. What are the weights of 16mm, 12mm, 20mm, 25mm, 8mm Dia. Bars.

22. What is the minimum Propping Period of Beams and Slabs of various Spans?

23. What are the advantages of Prestressed Concrete over R.C.C?

24. Quantity of materials required for different works.

25. Which is stronger solid steel rod or hollow steel pipe?

26. Initial & final setting time of concrete?

27. Why we provide steel in concrete?

28. Is brick strength more or concrete block?

29. How many bricks are there in 100cft?

30. 28 days compressive strength of concrete in PSI?

31. How to calculate the unit weight of steel bars?

32. What is Plinth Level and Sill Level?

33. What is Brest Wall?

34. What is Brick crushing strength(PSI)?

35. How many are the types of joints?

36. How can cracks in concrete be avoided?

37. Types Of DPC and its Thickness used?

38. 28 Days Strength of Concrete (1:2:4)?

39. How many types of slabs are there & how to design it?

40. How much is the cover for slab?

41. Maximum % of Steel in columns and beams?

42. What is fineness modulus?

43. What is Packing Factor?

44. Difference between one way slab & two way slab?

45. Difference between QA & QC?

46. What do you mean by Fe415?

47. What are the functions of a column in a building?

48. How many feet are in 4 square yards?

49. What is the average density of soil?

50. What is the ratio of Grades M5, M7.5, M10, M15, M20, M25, M30, M35, M40?

51. Why foundation is provided?

52. The concrete slump recommended for beams and slabs; is-

53. What is the meaning of soil reinforcement?

54. What is the different type of slump test indications?

55. What is buckling or crippling load?

56. Define slenderness ratio. What is its effect on the design of compression member?

57. Shear force and BM diagrams for different types of loadings on beams.

58. Difference between mild steel and HYSD bars?

59. What do you understand by 80/100 bitumen?

60. What is differential settlement?

61. What do 53 stands for in 53-grade cement?

62. How do you construct a 25 storey building with no columns?

63. Types of loads on structure?

64. Difference between pre-tensioning and post-tensioning?

65. What is the L/D ratio of a cantilever beam?

66. What is camber?

67. What is batching? Difference between volume and weight batching?

68. How is a theodolite leveled?

69. What is a benchmark? Name the different types.

70. Types of admixtures?

71. What are the CAD softwares you have used?

72. Interpret a strss vs strain curve.

73. Define modulus of elasticity.

74. What are the chemical compositions of cement?

75. What is creep & shrinkage of concrete?

Skin Friction of Soil

Skin Friction of Soil

Skin friction of soil is considered in pile designs. Mainly, there are two types of skin frictions. Negative and positive skin friction are considered in pile designs.

Earthquake Shaking Force, 3D vector sum of ground accelerations

Earthquake Shaking Force, 3D vector sum of ground accelerations

The formula for calculating the Earthquake force of the local ground motion is:

Rigid Frame Formulas by Kleinlogel

Important structural engineer manual about 

RIGID FRAMES FORMULAE

Combined Footing

What is Combined Footing?

A footing when used for two columns or more than two columns is called combined footing. Combined footing is mainly two types.

Rectangular Combined Footing.

Trapezoidal Combined Footing.

.

This type of footing is provided under following situations:

1. When the columns are located extremely close to each other and their individual footings are overlapping.

2. In case of soil having low bearing capacity and a large area is required under the individual footing.

3. When the column end is situated near the property line and it is not possible to extend the footing area on the side of the property line.

The main purpose of using combined footing is to distribute uniform pressure under the footing. To accomplish this target, the center of gravity of the footing area should be equal to the center of gravity of the two columns.

If the outside columns close to the property line, conveys heavier load, it is necessary to provide trapezoidal footing to maintain the center of gravity of the footing in line with the center of gravity of the two column loads. Otherwise only a rectangular footing may be provided. Following extra points should be kept in view to provide combined footings.

1. This type of footing is considered as an inverted floor, where footing load is carried by the columns and loaded from underneath by uniform earth reaction.

2. The area enclosed by combine footing should be equivalent to or more than that acquired by dividing the total combined load into the columns by safe bearing capacity of the soil.

3. The shape of the combined footings should be selected in such a manner that it concurs the center of gravity with the center of gravity of soil reaction.

JW Marriott Marquis Dubai Hotel

JW Marriott Marquis Dubai Hotel

Height: 355 meters (1166 feet)

JW Marriott Marquis Dubai Hotel is a complex of two supertall towers in Dubai. Although at here they are referred to as the tallest twin towers used for hotels, the 355m towers are actually also the tallest hotel buildings in the world. There are 3 buildings in the world that possess higher hotels, respectively are Abraj Al Bait, International Commercial Center and the Shanghai Tower, but all of them are not purely used as hotels, Emirates Towers are still the tallest all-hotel buildings, there are 1608 suits within the twin towers.

DIFFERENCE BETWEEN ENGLISH BOND AND FLEMISH BOND

DIFFERENCE BETWEEN ENGLISH BOND AND FLEMISH BOND:

1-English bond is much stronger than flemish bond for the walls thicker more than 1½ brick.

2-Flemish bond shows more attractive and pleasing appearance of masonry work.

3-Flemish bond is economical as it uses broken brick bats, although it requires some extra mortar for additional joints.

4-Uses of flemish bond is a bit difficult than english bond. Flemish bond requires more skilled labour and supervision.

Note :

Flemish bond can be sub-divided into two different categories :

a- Double flemish bond

b- Single flemish bond and

The Lotus Temple

What is The Lotus Temple?

The Lotus Temple is a House of Worship located in New Delhi,India. 

The structure was completed in 1986. 

This structure is notable for its flower like shape. 

This place of worship serves as the Mother Temple of the Indian subcontinent.

Due to its peculiar structure, it has become a prominent attraction in the city. 

The Lotus Temple has won numerous architectural awards and been featured in hundreds of newspaper and magazine articles.

Polymer concrete

What is Polymer concrete?

Polymer concrete is an ordinary concrete produced with OPC (Ordinary portland cement) wet cured and inseminated with liquid or vaporous chemical compound (Methyl methacrylate monomer) and polymerized by gamma radiation or with chemical initiated implies, i.e by utilizing thermal catalytic method (Adding 3% Benzoyl peroxide) to the monomer as a catalyst. The impregnation is helped by drying the concrete at an extreme temperature by evacuations and absorbing the monomer under limited pressure.

TYPES OF POLYMER CONCRETE:

Polymer concrete can be classified in following three categories:

1. Polymer impregnated concrete (PIC).

2. Polymer cement concrete (PCC).

3. Polymer concrete (PC).

ADVANTAGES OF POLYMER CONCRETE:

1. It has high impact resistance and high compressive strength.

2. Polymer concrete is highly resistant to freezing and thawing.

3. Highly resistant to chemical attack and abrasion.

4. Permeability is lower than other conventional concrete.

Concrete process in hot weathe

Concrete process in hot weather:

We know that cement possesses faster rate of hydration in hot weather. The rate of hydration of cement increases with the increases in temperature. Generally, 10 C – 27 C is considered as most suitable for hydration.

At higher temperature, the concrete may start to set before placing and compacting in position. Therefore the concrete should be placed as fast as possible after mixing. During concreting in hot climatic condition, the concrete may have to be cooled to protect from ill effects. To achieve this, cooled water and aggregates can be used while preparing the concrete.

PRECAUTIONS BEFORE, DURING & AFTER CONCRETING:

1. The main aim is to decrease the temperature of the concrete itself and furthermore the forms where it will be placed.

2. If possible, mixer machine should be installed below the shade.

3. If concrete is to be transported to a longer distance, concreting materials may be mixed first in dry condition and the water may be included at the job site just before placing the concrete in position.

4. To protect the water content from evaporation, always deep containers should be used for the transportation of concrete.

5. After placing, wet burlap should be used to cover the concrete. It will help to protect coolness and moisture of concrete.

6. Curing should be started immediately as soon as the concrete starts hardening.

7. Retarding admixtures can also be used while adding the water in the mix to slow down the setting action of concrete.

8. Ice cubes or refrigerator can be used to cool the water to be used. But ensure that ice cubes are totally melted and there are no solid ice crystals present in the concrete.

Information about Solar Energy system for roof

Information about Solar 

Energy system for roof:

Solar energy is an eco-friendly alternative method of generating electricity. In simple terms, this process involves using the Sun’s rays (photons) to stimulate metal sheets in order to loosen electrons from the metal. 

These electrons then break free of the metal sheets and form a flow of electricity .

These metal sheets are comprised of multiple layers of photovoltaic cells , which convert sunlight into electricity,linked together to form larger solar panels. 

These photovoltaic cells are often composed of silicon, which is a substance commonly used in microelectronics. 

These cells function by having one sheet of silicon being positively charged which is called the p-type, while the other is negatively charged, called the n-type .

This results in a magnetic field across the cell. 

Due to this, when the sun strikes the side that is negatively charged (stocked with extra electrons), the electrons that are knocked loose are pushed across this magnetic field through a junction of the two sheets towards the positively charged sheet. The cell is also encased in an electrode which is where wiring and energy transfer take place. 

One more key component to the photovoltaic cell is the reflection-resistant film which allows the most sunlight to pass through to the silicon layers.

A technical depiction of a solar cell’s construction can be seen in figure .