can any one clarify my following qurries

[Srinivasan]

1. Why the wet process of has been replaced nowadays with dry process of manufacturing of
cement
2. What is the effect of Rate of heating and cooling on properties of cement during its
manufacturing?
3. How Gypsum quantity in cement affect the setting of cement?
4. Write details note on Specification for Portland Cement (ASTM C150)?
5. What is the effect of fineness, akali, Loss of ignition on properties of cement and why?
6. Why the rate of strength gain in the Figure shown in Slide 41 is different for different types
of cement? Explain?
7. How the rate of hydration is affected by fineness and water cement ratio?
8. Which type of cement will you prefer in the following conditions and why?
 Mass concreting
 Cold weather concreting

 

[Tejas Jain]

I have attached file which will give specification for portland cement ASTM C150

 

[Salman001]

3.Gypsum acts as retarder and slows down the hydration process so concrete remains in plastic zone more time an workable for long time and so sets slowly so initial setting time increase

 

[Dnyan Deshmukh]

1. Why the wet process of has been replaced nowadays with dry process of manufacturing of
cement

Because it is easier and gives better results.

2. What is the effect of Rate of heating and cooling on properties of cement during its
manufacturing?

It impacts on formation of compounds and free lime in Cement.

3. How Gypsum quantity in cement affect the setting of cement?

C3A can increase setting of cement faster, also the clinkers reacts faster with water, Gypsum delays the process depending on the dosage and chemical composition of cement.

5. What is the effect of fineness, akali, Loss of ignition on properties of cement and why?

Fineness increase water demand and also makes faster reaction, resulting into high early strength, I am not sure about Alkali and loss of ignition. Alkali may react with aggregates. Loss on ignition above 5% indicates the high free lime which can cause problem in soundness and durability of the structure due to expansion in set concrete by reaction of free lime.

6. Why the rate of strength gain in the Figure shown in Slide 41 is different for different types
of cement? Explain?

Because of there chemical composition and fineness, C3S makes faster reaction and responsible for early strength gain up to 7 days, C2S reacts slowly but forms high bonds compare to C3S and responsible for later age strength gain. Variation in its % makes the variation but ultimate strength is almost same.

7. How the rate of hydration is affected by fineness and water cement ratio?

Fineness of cement increases the surface area of cement which requires higher water to cover it. more the fineness, more will be rate of gain in strength at early ages, after gel formation hydration of some particles may not take place due to water is not able to reach it.

8. Which type of cement will you prefer in the following conditions and why?
 Mass concreting
 Cold weather concreting

For Mass Concrete blended cement like PPC or PSC is suitable which generate low heats in hydration and also generate low strength at early ages. but as its a mass concrete, there is no hurry of de-shuttering, mostly mass concrete is done at foundation level so delayed strength gain is acceptable as structure is not going to get fully loaded before the concrete achieve its full strength.

For Cold Weather concrete - rapid hardening cement will be most preferred due to its high strength gain, almost 7 days strength in 3 days. Also the generated heat during hydration process will prevent water in concrete from freezing.