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Sunday, 9 April 2017

Interview 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




Next Article will be : Types of cement and difference between OPC , PPC cement , Where and when they will use .... Many more.... soon.....




Saturday, 8 April 2017

TOP 7 : STEEL STRUCTURE




1: With percentage increase of carbon in steel , decreases its
A: Strength
B: Hardness
C: Brittleness
D: Ductility  

2:Poisson's ratio for steel within elastic limit , ranges from
A: 0.15 TO 0.20
B: 0.25 TO 0.24
C: 0.25 TO 0.33
D: 0.33 TO 0.35

3: The slenderness ratio of a column is zero when its length 
A: IS ZERO
B: IS EQUAL TO ITS RADIUS OF GYRATION
C: IS SUPPORTED ON ALL SIDES THROUGHOUT ITS LENGTH
D: IS BETWEEN THE POINTS OF ZERO MOMENTS

4:Maximum permissible slenderness ratio of compression members which carry dead and superimposed load, is
A:350
B:250
C:180
D:80

5:The effective length of a weld, is taken as the actual length
A: Minus the size of weld
B: Minus twice the size of weld
C: Plus the size of weld
D: Plus twice the size of weld

6:A beam is defined as a structural member subjected to
A: Axial loading
B:Transverse loading
C: Axial and transverse loading

7:The best compression member section for column is:
A: Single angle section
B: Double angle section
C: Channel section
D: I-section




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%

Thursday, 6 April 2017

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


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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