Interviews and Exams questions : ALL About Cement

1: Name the component that responsible for early strength of concrete:

Ans: C3S ( Tri Calcium silicate ) , that react with water and produces more heat of hydration is responsible for early strength of concrete.

2: Which compound contribute to the later strength of concrete ?

Ans: C2S ( Di Calcium silicate ) that hydrates slowly , contribute to the later strength of concrete .

3: After how many days , the compressive strength developed by C3S and C2S are equal .

Ans: ONE year  

4:For road rapid work which type of cement is recommended :

Ans: Rapid hardening cement

5: In how many  days , about 50% of the total heat evolution occurs.

Ans: During the first 3 days of hydration 

6:Which oxides are responsible for high early strength of cement ?

Ans: High total alumina and high ferric oxide content favour the production of high early strength in cement

Compounds : When components of cements added up with water than they called compound in simple language ..

Tricalcium Silicate (C3S) hardens rapidly and is largely responsible for initial set and early strength.

In general, the early strength of portland cement concrete is higher with increased percentages of C3S.

Dicalcium Silicate (C2S) hardens slowly and contributes largely to strength increases at ages beyond 7 days.

Tricalcium Aluminate (C3A) liberates a large amount of heat during the first few days of hardening and, together with C3S and C2S may somewhat increase the early strength of the hardening cement (this effect being due to the considerable heat of hydration that this compound evolves). It does affect set times.

Tetracalcium Aluminoferrite (C4AF) contributes very slightly to strength gain. However, acts as a flux during manufacturing. Contributes to the color effects that makes cement gray.aakes cement gray.

Compounds by percentage :

Role of compounds on properties of cement : MOST IMP

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3: http://amzn.to/2iOjtqm

RCC Book: Best suitable for deep study :
1: http://amzn.to/2iMfgUj (Reinforced Concrete Design - Third Edition ) by Devdas Menon (Author), S. Pillai (Author)

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Los Angeles Abrasion Test , Why and How To Perform

LOS ANGELES ABRASION TEST:

This is hardness test for aggregates, used in Laboratory  to determine the hardness value or abrasion value 

APPARATUS :

 Los Angeles Abrasion Testing Machine ,

Abrasive Charge – Cast iron or steel balls ,
Test sieve – 1.70 mm IS sieve ,

 Balance of capacity 10 kg , Oven , Tray

The aggregate used in surface course of the highway pavements are subjected to wearing due to movement of traffic. 

When vehicles move on the road, the soil particles present between the pneumatic tyres and road surface cause abrasion of road aggregates. 

The steel reamed wheels of animal driven vehicles also cause considerable abrasion of the road surface. 

Therefore, the road aggregates should be hard enough to resist abrasion. 

The principle of Los Angeles abrasion test is to produce abrasive action by use of standard steel balls which when mixed with aggregates and rotated in a drum for specific number of revolutions also causes impact on aggregates. 

The percentage wear of the aggregates due to rubbing with steel balls is determined and is known as Los Angeles Abrasion Value.

Key point of los angles test:

Rotate the machine at a speed of 30 – 33 revolutions per minute. The number of revolutions is 500 for grading A, B, C & D and 1000 for grading E, F & G. The machine should be

5 kg of sample for grading A, B, C & D and 10 kg for grading E, F & G

THE CALCULATION PART:

Original weight of aggregate sample = W1 g

Weight of aggregate sample retained = W2 g

Weight passing 1.7mm IS sieve = W1 - W2 g

Los Angeles Abrasion Value = (W1 - W2) / W1 X 100

Los angeles abrasion value should lies in below given range for different types of roads

Types of pavement layers                                         Max. Permissible Abrasion Value in %

1:WBM , SUB BASE COURSE                                                      60%

2:WBM BASE COURSE WITH BITUMEN SURFACE               50%

3: BITUMEN BOUND MACADAM                                             50%

4:WBM SURFACING COURSE                                                    40%

5: BITUMINOUS PENETRATION MACADAM                              40%

6:BITUMINOUS SURFACING DRESSING CEMENT
 CONCRETE SURFACING COURSE                                              35%

7:BITUMINOUS CONCRETE SURFACING COURSE                   30%

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TOP RCC QUESTIONS PART 2

12: The percentage of minimum reinforcement of the gross sectional area in slabs is:
A: 0.10%
B:0.12%
C:0.15%
D:0.18%

13: The amount of reinforcement for main bars in a slab is based upon:
A: Minimum bending moment
B: Maximum bending moment
C:Maximum shear force
D: Minimum shear force

14: In under reinforced singly reinforced beam , concrete crushes at its maximum strain
A: 0.35 %
B: 0.24%
C: 0.30%
D:0.20%

15: The maximum area of tension reinforcement in beams shall not exceed
A:0.15%
B:1.5%
C:4%
D:1%

16: A raft foundation is provided if its area exceeds the plan area of the building by: 50%

17: For a number of columns constructed in a row , the type of foundation provided is: Strip 

18 : As per IS :456, the reinforcement in a column should not be less than : 0.7 % and more than 7% of cross sectional area

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TOP 11 RCC Questions

1:The column is regarded as long column if the ratio of its effective length and lateral dimension , exceeds :
A: 10
B:15
C:20
D:35

2:The weight of foundation is assumed as?

A: 5% OF WALL WEIGHT 
B: 7% OF WALL WEIGHT 
C: 10% OF WALL WEIGHT
D: 12 % OF WALL WEIGHT


3:The shear reinforcenent in R.C.C. is provided to resist
A: VERTICAL SHEAR 
B: HORIZONTAL SHEAR 
C: DIAGONAL COMPRESSION
D: DIAGONAL TENSION 




4: An R.C.C.column is treated as short column if its slenderness ratio is less than: 50 ( Most IMP)

5: An R.C.C.column is treated as long column if its slenderness ratio is greater than: 50 (Most IMP)


6: As per I.S. 456-1978, the PH value of water shall be:
A: Less than 6
B: Equal to 6
C: Note less than 6
D:Equal to 7

7:The maximum area of tension reinforcement in beams shall not exceed : 4%

8: The steel generally used in RCC work : Mildsteel 

9: The diameter of main bars in RCC columns , shall not be less than : 12 mm

10: The characteristic strength of concrete is usually referred to:
A: 5 Days cube strength
B: 7 Days cube strength
C: 21 Days cube strength
D: 28 Days cube strength

11: Thickness of slab is taken:
A: 0.10d
B:0.20 d
C: 0.15d
D:0.25d



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BAR BENDING SCHEDULE IMP

You may also like this topic of Estimation: 

How to calculate Quantity of Cement :Sand: Aggregate

If you are searching some important interview questions about cement than this article will boost your  knowledge today. 

                       Cement : The backbone of construction

Civil Engineering Competitive Exams Books :
For GATE Aspirants :
1: http://amzn.to/2A4iy9K
2: http://amzn.to/2hqwfrR ( more preferably)For SSC JE Aspirants :
1: http://amzn.to/2hqwfrR
2: http://amzn.to/2z7CGtm ( Highest rated book for SSC JE)
3: http://amzn.to/2iOjtqm

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BURJ KHALIFA : THE NAME TELLS EVERYTHING== >>

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10 Tallest Bridges In The World== >

1. Millau Viaduct, France – 343 metres (1,125 ft) tall. Opened in 2004, this 4 lanesbridge is a cable-stayed bridge that spans the valley of the River Tarn near Millau in southern France. The bridge has 7 piers of different heights. The second one is the tallest with a height of 244.96 m (803 ft 8 in) – making it the tallest structure in France, taller than the Eiffel Tower!

2. Russky Bridge, Russia – 320.9 metres (1,053 ft) tall. Located in Vladivostok, the bridge was completed in 2012. It connects the mainland part of the city with Russky Island

3. Sutong Bridge, China – 306 metres (1,004 ft) tall. Opened in 2008, this bridge spans the Yangtze River between Nantong and Changshu

4. Akashi-Kaikyo Bridge, Japan – 298.3 metres (979 ft) tall. This beautiful suspension bridge was opened in 1998. It links the city of Kobe on the mainland of Honshu to Iwaya on Awaji Island. It is the tallest suspension bridge in the world

5. Stonecutters Bridge, Hong Kong – 298 metres (978 ft) tall. A high level cable-stayed bridge which spans the Rambler Channel in Hong Kong, connecting Nam Wan Kok, Tsing Yi island and Stonecutters Island. The bridge deck was completed and opened to the public in 2009

6. Yi Sun-sin Bridge, South Korea – 270 metres (890 ft) tall. Except of being the 6th tallest bridge in the world, it’s also the second tallest suspension bridge in the world and the fourth longest suspension bridge in the world

7. Jingyue Bridge, China – 265 metres (869 ft) tall. This cable-stayed bridge in Jianli County was opened in 2010 and crosses the Yangtze River

8. Great Belt East Bridge, Denmark – 254 metres (833 ft) tall. Opened in 1998, this bridgeruns between the Danish islands of Zealand and Funen. It is the third tallest bridge in Europe

9. Zhongxian Huyu Expressway Bridge, China – 247.5 metres (812 ft) tall. Completed in 2010, this bridge crosses the Yangtze River in Zhong County

10. Jiujiang Fuyin Expressway Bridge, China – 244.3 metres (802 ft) tall. A Cable-stayed bridge under construction and should be completed by the end of 2013. With a main span of 818 m (2,684 ft) it will become one of the longest cable-stayed bridges in the world upon its completion

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10 Highest Bridges In The World = =>>

1. Sidu River Bridge, China – Height of 496 m (1,627 ft). This 1,222 m (4,009 ft) long suspension bridge is the world’s highest bridge since 2009. Located in the Hubei Province, it  crosses the valley of the Sidu River

2. Baluarte Bridge, Mexico – Height of 403 m (1,322 ft). A cable-stayed bridge, located along the Durango–Mazatlán highway. The bridge has a total length of 1,124 m (3,688 ft), the second-highest bridge overall

3. Baling River Bridge, China – Height of 370 m (1,210 ft). A suspension bridge in Guizhou Province. The bridge spans over the Baling River Valley. The bridge has a total length of 2,237 m (7,339 ft)

4. Beipanjiang River 2003 Bridge, China – Height of 366 m (1,201 ft). A suspension bridge in Guizhou Province. The bridge has a span width of 388 metres. Between 2003 and 2005, it was the world’s highest bridge

5. Aizhai Bridge, China – Height of 350 m (1,150 ft). A suspension bridge in Hunan, China. It is the world’s highest and longest tunnel-to-tunnel bridge

6. Beipanjiang River 2009 Bridge, China – Height of 318 m (1,043 ft). A suspension bridge in Guizhou Province. It crosses the Beipan River. It was opened to the public in 2009, just 6 years after another (and higher) bridge crossing the same river was opened (see number 4 in this list)

7. Liuguanghe Bridge, China – Height of 297 m (974 ft). A beam bridge in Guizhou, China. It held the record for world’s highest bridge between 2001 and 2003. It is still the highest beam bridge in the world

8. Zhijinghe River Bridge, China – Height of 294 m (965 ft). The highest arch bridge in the world. The bridge crosses the valley of the Zhijinghe River and is opened to the public since 2009

9. Royal Gorge Bridge, Colorado, United States – Height of 291 m (955 ft). The Royal Gorge Bridge is a tourist attraction within a theme park. The bridge deck crosses the Royal Gorge 955 feet (291 m) above the Arkansas River, and held the record of highest bridge in the world from 1929 until 2001. The bridge is 1,260 feet (384 m) long It is the highest in the United States

10. Beipanjiang River Railway Bridge, China – Height of 275 m (902 ft). The world’s highest railway bridge. The bridge spans a deep canyon on the Beipan River in Guizhou province. This is the third bridge within this list spanning over the Beipan river

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Reinforced Concrete Beam Design : Failure Mode

In reinforced concrete beam design, failure is designed for safety. If the structure fails by sudden crushing, huge damage and loss of life may take place. So, it is designed so that structure would give a warning before collapse. Reinforced concrete beam failure may take place in 3 ways.

1. Concrete failure: Crushing of concrete
2. Steel failure: Yielding by steel
3. Concrete & steel combined failure

Concrete Failure

In concrete failure, concrete reaches to its ultimate strength before steel reaching to its yield point. As a result concrete crushes down before steel yields. This type of beam failure is unwanted as the concrete crushes without giving any warning. Concrete failure occurs due to the following reasons.
1.       If large amount of reinforcement is used.
2.       Compressive strength of concrete is less than tensile strength of steel.
3.       Sudden destruction occurs without giving any warning.

Steel Failure

In steel failure, steel reaches to its yield point before concrete reaches to its ultimate strength. So, steel yields before crushing of concrete which gives ample warning to the inhabitants. So, steel failure is preferable during structure design. Some common notes on steel failure of rcc beams are given below.
1.       Relatively moderate amount of reinforcement are employed.
2.       Tensile strength of steel is less than compressive strength of steel.
3.       Steel yields and stretches and tension crack propagates concrete cracks.
4.       Secondary compression failure.
5.       Steel failure of rcc beams gives ample warning to the inhabitants. So, damage can be avoided.
6.       For engineering, steel failure is preferable.

Combined Concrete Beam Failure

In this type of failure, concrete and steel fails at the same time. That means concrete should reach to its ultimate strength just at the same time when steel fails so that both fails together. Combined failure is practically almost impossible because it is not possible to tell the exact behavior of concrete & steel so that they fail at the same time.

Basic Reinforced Concrete Beam Design Question

Question: Which type of failure is preferable in design of reinforced concrete beam?

Answer:  Steel failure. It gives ample warning to the inhabitants reducing the damage.

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Reinforced Cement Concrete : Advantages of RCC

RCC (Reinforced Cement Concrete)

RCC (Reinforced Cement Concrete) is the combination of using steel and concrete instead of using only concrete to offset some limitations. Concrete is weak in tensile stress with compared to its compressive stress. To offset this limitation, steel reinforcement is used in the concrete at the place where the section is subjected to tensile stress. Steel is very strong in tensile stress. The reinforcement is usually round in shape with approximate surface deformation is placed in the form in advance of the concrete. When the reinforcement is surrounded by the hardened concrete mass, it form an integral part of the member. The resultant combination of two materials are known as reinforced concrete. In this case the cross-sectional area of the beam or other flexural member is greatly reduced.

Advantages of RCC

Nowadays, RCC is used in most of the structures. The advantages of RCC (Reinforced Cement Concrete) are as following.

1. Reinforced Cement Concrete has good compressive stress (because of concrete).
2. RCC also has high tensile stress (because of steel).
3. It has good resistance to damage by fire and weathering (because of concrete).
4. RCC protects steel bars from buckling and twisting at the high temperature.
5. RCC prevents steel from rusting.
6. Reinforced Concrete is durable.
7. The monolithic character of reinforced concrete gives it more rigidity.
8. Maintenance cost of RCC is practically nil.

It is possible to produce steel whose yield strength is 3 to 4 time more that of ordinary reinforced steel and to produce concrete 4 to 5 time more stronger in compression than the ordinary concrete. This may high strength material offer many advantages including smaller member cross-sections, reduce dead load and longer spans. But the high stress result in high strain and consequently large deflection of such member will occur under ordinary loading conditions. Also high strength reinforcing steel would include large crack in the concrete which reduce the durability of the structure. The commonly used yield strength of high strength reinforcing steel is 60 ksi.

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