Cement | solution of questions set | Grade 12 | Chemistry 

1 a. What are the main compositions of Portland cement?

b. What are the main functions of alumina and lime in the production of cement?

c. Which is better OPC or PPC cement?

a. Portland cement is made up of four main compounds: tricalcium silicate (3CaO.SiO_{2}) . dicalcium silicate (2CaO SiO₂), tricalcium aluminate (3CaO.Al_{2}O_{3}) and a tetra-calcium aluminoferrite (4CaO Al2O3Fe2O3) 

b. Function of: Lime: It provides high water retention that allows for maximum early curing of the cementitious materials.

Alumina: It imparts quick setting property to the cement.

c. PPC has a lower heat of hydration and it is prone to fewer cracks compared to OPC. PPC has lower strength than OPC but PPC provides better workability and finishing than OPC. PPC provides greater resistance to chemicals.

2. a. Write the name of three raw materials which are used in Portland cement.

b. What are the grade of cement?

c. What is concrete? What is the main composition of concrete?

a. The raw material that is used in the manufacturing of Portland cement mainly consists of lime, silica, alumina and iron oxide.

b. Generally, there are three grades of cement available in the market i.c. 33 grade, 43 grade and 53 grade

c. Concrete is a mixture of cement, air, water, sand, and gravel. The main composition of concrete are 10% cement, 20% air and water, 30% sand, and 40% gravel.

3. a. Write two advantages of OPC and PPC cement?

b. Write two important properties of fineness of Portland cement.

c. What are the main challenge for establishing cement factory in Nepal?

a. Advantage of OPC

• It has high compressive strength in the early stages.
• It contains low alkali content which provides better protection against alkali-aggregate reaction

Advantage of PPC

• It produces a very slow rate of heat of hydration and also reduces the heat.
• The particle size of PPC is smaller than OPC, so it reduces microcracks.

b. Two importance of fineness of portland cement

• Finer cement offers a greater surface area for hydration and hence faster the development of strength.
• If particles are of small size. It's surface area increase. This adhesion between them is increased.

c. The biggest issue is a lack of electricity, which prevents the industries from realizing all of their potential. Similar difficulties with the supply of raw materials, as well as challenges with labor and transportation, occasionally hamper us.

4 a. How fineness of cement affects strength gain?

b. Draw the flow sheet diagram for the production of Portland cement.

c. Write the chemical reactions which are involved in the burning zone of production of cement.

a. Hydration rate is influenced by cement fineness. More surface area is available for water-cement interaction per unit volume the smaller the particle size. As a result, finer cement reacts with water more quickly and gains strength sooner.

b. Flow sheet diagram for the production of portland cement is given as:

c. In burning zone temperature is maintained up to 1500°C and the oxide formed in above zones combine together and form respective silicate, aluminates and ferrite. 

2CaO + SiO₂ → 2CaO·SiO₂   

3CaO + SiO₂ → 3CaO·SiO₂
3CaO + Al₂O₃ → 2CaO·Al₂O₃

2CaO + Al₂O₃ → 2CaO·Al₂O₃

4CaO + Al₂O₃ + Fe₂O₃ → 2CaO·Al₂O₃·Fe₂O₃

5 a. How is Portland cement made?

b. What are the grades of ordinary cement? Which one is better for construction work?

c. Write a reaction which involves in OPC cement.

a. Limestone and clay or other silicate mixtures are heated to high temperatures (>1500°C) in a revolving kiln to produce Portland cement. After cooling, the resultant clinker is combined with gypsum (calcium sulfate) and pulverized into a fine, homogenous powder. 

b. 33-grade OPC as is common. Buildings are constructed with the highest grade of 43 grade cement. Buildings are constructed using 43 grade cement.

c. The reaction which are involved in production of OPC cement are as:

3CaO.Al₂O₃ + 6H₂O → 3CaO.Al₂O₃.6H₂O (C₃A)   

(3CaO.SiO₂) + 6H₂O → 3CaO.2SiO₂.3H₂O + 3Ca(OH)₂

3(2CaO.SiO₂) + 6H₂O → 3CaO.2SiO₂.3H₂O + 3Ca(OH)₂

6 i. What is Portland cement? Name the major compositions of Portland cement.

ii. Define the term clinker

i. Portland cement: Portland Cement (PC) is a fine powder which is produced by heating limestone and clay minerals in a kiln and forms clinker.

Composition: Portland cement is made up of four main compounds: tricalcium silicate (3CaO.SiO_{2}) dicalcium silicate (2CaO SiO2), tricalcium aluminate (3CaO.Al_{2}O_{3}) and a tetra-calcium aluminoferrite (4CaO. Al_{2}O_{3}Fe_{2}O_{3})

ii. Clinker: Clinker is a granular material produced during the kilning step of cement manufacture that is utilized as a binder in a variety of cement products.

_{7 i.} What is Portland cement?

ii. Name the major components present in Portland cement.

iii. Why is gypsom used in clinker during cement production process?

iv. Give any two instruments used for the quality control of cement.

i. Portland cement: Portland Cement (PC) is a fine powder which is produced by heating limestone and clay minerals in a kiln and forms clinker.

ii. Composition: Portland cement is made up of four main compounds: tricalcium silicate (3CaO.5iO_{2}) dicalcium silicate (2CaO SiO2), tricalcium aluminate (3CaO.Al_{2}O_{3}), and a tetra-calcium aluminoferrite (4CaO,Al_{2}O_{3}Fe_{2}O_{3})

iij. Gypsum is typically added to clinker to avoid flash setting of the cement, but it is also very effective in facilitating clinker grinding by reducing agglomeration and coating of the powder on the surface of the balls and mill wall. 

iv. Two instruments a) X-ray fluorescence spectrometer b) Flame photometer are used for the quality control of cement

Full solution of chapter cement chemistry grade 12, solution of old is gold, neb solution of model questions