Civil Engineering - Building Materials - Discussion

10. 

In the cement the compound quickest to react with water, is

[A]. Tricalcium aluminate
[B]. Tetra-calcium alumino-ferrite
[C]. Tricalcium silicate
[D]. Dicalcium silicate.

Answer: Option A

Explanation:

No answer description available for this question.

Sinduja said: (Aug 22, 2013)  
Water react with cement. It is a dicalcium silicate. Then why it is tricalcium aluminate?

Piyush Singh said: (Nov 9, 2013)  
Water reacts with cement is true, but it is dicalcium silicate is the wrong one you predicted, its made up of 4 contents, dicalcium silicate, tricalcium silicate, tricalcium aluminate and tetracalcium alumino-ferrate. Dicalcium silicate gives the strength up to last stage, while tricalcium silicate gives the strength in initial phase like upto firth some days, while tricalcium silicate react instantly as false setting but its role in giving strength is very poor. Mainly dicalcium silicate and tricalcium silicate gives the strength to the concrete in later stage and initial stage respectively. But false setting reaction first is done by tricalcium aluminate.

Sharad said: (Dec 3, 2013)  
What is false setting reaction?

Kavya said: (Mar 6, 2014)  
C 3A :

Tricalcium Aluminate reacts most strongly with water of all the calcium aluminates. Its hydration leads to the phenomenon of "flash set" (instantaneous set) , and a large amount of heat is generated. To avoid this, Portland-type cements include a small addition of calcium sulfate (typically 4-8%). Sulfate ions in solution lead to the formation of an insoluble layer of ettringite over the surface.

Tricalcium aluminate is associated with three important effects that can reduce the durability of concrete:

1. "Overheating" in large masses of concrete.

2. Formation ettringite in sulfate attack, This reaction is expansive, and can "disrupt mature concrete".

3. Delayed ettringite formation, where "concrete is cured at temperatures above the decomposition temperature" of ettringite (about 65'C). On cooling, expansive ettringite formation takes place.

Because they are even more basic, the alkali-loaded polymorphs are correspondingly more reactive. Appreciable amounts (>1%) in cement make set control difficult, and the cement becomes excessively hygroscopic. The cement powder flowability is reduced, and air-set lumps tend to form.

They withdraw water from gypsum on storage of the cement, leading to false set. For this reason, their formation is avoided.

Podi Wije said: (Apr 7, 2015)  
What about tetracalcium alumino ferrite C4AF?

Sanjay said: (Jun 27, 2015)  
Definitely its di-calcium silicate not tri-calcium aluminate.

Shashank Tyagi said: (Dec 23, 2015)  
It is not di calcium silicate its tri calcium aluminate because it has highest affinity toward water and generate more heat about 809 kJ/kg more than C2S.

It react with h2o to form false set rich hinder other strength giving reaction. That hy gypsum is added to react it c3a to form tranzite.

Jitendra said: (May 18, 2017)  
The Rate of hydration is more for C4AF then how C3A react first?

Parameshwar said: (Jun 22, 2017)  
C3a qukist react btt c3s fst react with water.

Ravinder Poonia said: (Sep 1, 2017)  
Yes, the correct answer A. I agree.

Ram said: (Oct 26, 2017)  
C3A is characteristically fast reacting with water and may lead to an immediate stiffening of paste and this process is termed as a flash set. The role of gypsum added in the manufacture of cement is to prevent such a fast reaction.

Sumant said: (Jan 8, 2018)  
C4af is involve first in rate of hydration.

Yasir said: (Mar 3, 2018)  
Tricalcium aluminate results into flash setting of cement and in order to prevent flash setting Gypsum is added.

Rabindra said: (Apr 10, 2018)  
What is the difference between false set and flash set of cement?

Rabindracbs@Gmail.Com said: (Apr 10, 2018)  
What is Ettringite?

Rabindra said: (Apr 10, 2018)  
Flash set is the property of concrete by which upper surface of concrete become hard without setting the inner portion.

Rabindra said: (Apr 10, 2018)  
Flash set is the property of concrete by which upper surface of concrete become hard without setting the inner portion.

Karun said: (Apr 11, 2018)  
I think C4AF is the right one because it reacts instantly with water where C3A produces the highest heat of hydration so it sets quickly and produces volume Change.

Sharma said: (Apr 12, 2018)  
I think C4AF is the right one because the quantity of alumina in it is more as compare to C3A, alumina is responsible for quick setting for this it reacts instantly with water, so that's why it reacts quickly with water.

Abhishek said: (Apr 17, 2018)  
C4AF is quickest to react.

It has the highest rate of heat evolution among all other Bogue's compound.

Sandeep said: (Jul 8, 2018)  
Please correct this.

C4AF has the highest rate of hydration.

T-K Afridi said: (Aug 7, 2018)  
The Initial setting of Portland cement is due to tricalcium aluminate. Tricalcium silicate hydrates quickly and contributes more to the early strength.

Amri said: (Aug 8, 2018)  
C4AF is the correct answer.

Rajeev Ranjan said: (Aug 25, 2018)  
C4AF is the right answer.

Ram said: (Aug 26, 2018)  
Cement has 4 component.

1. C3S it is quickly hydrated and a short time in give strength.
2. C2s it is a set time long periods and alternative setting time.
3. C3af training Calcium Alumino-ferrite.

Amit Kumar said: (Dec 8, 2018)  
Cement has 4 compounds which are known as Bogue compound.

1. Tricalcium silicate: It gives early strength.
2. Dicalcium silicate: It gives ultimate strength.
It also decreases the heat of hydration.

3. Tricalcium Aluminate:it rapidly reacts with.
Water. It is also responsible for the initial setting. It has a high heat of hydration.

4: Tetracalcium Amino Ferrite: It produces less heat. If increase the content reduce the strength slightly.

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