Showing posts with label BUILDING MATERIAL. Show all posts
Showing posts with label BUILDING MATERIAL. Show all posts

Sunday 9 April 2017

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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2: http://amzn.to/2z7CGtm ( Highest rated book for SSC JE)
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RCC Book: Best suitable for deep study :
1: http://amzn.to/2iMfgUj (Reinforced Concrete Design - Third Edition ) by Devdas Menon (Author), S. Pillai (Author)


Saturday 8 April 2017

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%

Sunday 18 December 2016

Test for bricks


(1) Absorption:
A brick is taken and it is weighed dry. It is then immersed in water for a period of 16 hours. It is weighed again and the difference in weight indicates the amount of water absorbed by the brick. It should not in exceed 20 per cent of weight of dry brick.
(2) Compressive/Crushing strength of Bricks:
The crushing strength of a brick is found out by placing it in a compression testing machine. It is pressed till it breaks.  the minimum crushing or compressive strength of bricks is 3.50 N/mm2. 

The bricks with crushing strength in between of 7 N/mm2 to 14 N/mm2 are graded as A and those having above 14 N/mm2 are graded as AA, 
(3) Hardness test on bricks:
In this test, a scratch is made on brick surface with the help of a finger nail. If no impression is left on the surface, the brick is r sufficiently hard.
(4) Presence of soluble salts:
The soluble salts, if present in cause efflorescence on the surface of bricks. For finding out the presence of soluble salts in a brick, it is immersed in water for 24 hours. It is then taken out and allowed to dry in shade. The absence of grey or white deposits on indicates absence of soluble salts.

If the white deposits cover about 10 per cent surface, the efflorescence is said to be slight and it is considered as moderate, when the white deposits cover about 50 per cent of surface. If grey or white deposits are found on more than 50 per cent of surface, the efflorescence becomes heavy and it is treated as serious, when such deposits are converted into powdery mass.
(5) Shape and size:
In this test, a brick is closely inspected. It should be of standard size and its shape should be truly rectangular with sharp edges. For this purpose, 20 bricks of standard size (190 mm x 90 mm x 90 mm) are selected at random and they are stacked lengthwise, along the width and along the height.
(6) Soundness test on brick:
In this test, the two bricks are taken and they are struck with each other. 
The bricks should not break and a clear ringing sound should be produced.

Other test can be perform but these 6 are the important once.

Wednesday 17 August 2016

Wednesday 18 May 2016

How to calculate quantity of cement, sand , and aggregates



After doing all these calculation  you are now curious about knowing basics of cement , types of cement and which questions can be asked in interview or in written exams , am i right?
So here is the article about cement , don't miss it , its worth to read, 


Cement : The backbone of construction

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