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Assertion Setting of cement is an exothe...

Assertion Setting of cement is an exothermic process.
Reason It involves dehydration of calcium aluminates and calcium silicates.

A

Both A and R are true and R is the correct explanation of A

B

Both A and R are true but R is not a correct explanation of A

C

A is true but R is false

D

A is false but R is true
or (E) Both A and R are false.

Text Solution

Verified by Experts

The correct Answer is:
C
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Assertion : Setting of cement is an endothermic process. Reason : Setting of cement involves hydration and rearrangement of the molecules of calcium aluminates and calcium silicates.

Cement is one of the most important building material of the present time. It is a dirty greyish heavy powder containing calcium aluminates and silicates. The important raw materials neede for the manufacture of cement are limestone, clay and gypsum. the main step in the manufacture of cement is the heating of raw meal or slurru in the rotary kiln at a very high temperature 1400-1600^(@)C . Finally 2% or 3% gypsum is added. When cement is mixed with water and left as such for sometime, it becomes a hard mass. This is known as setting of cement. It is believed that varous aluminates and silicates present in the cement form hydrates with water which seperate in the form of gel. the gel formed start losing water partly by evaporation and partly by forming hydrates with unhydrated constituents. this results in the formation of a hard mass. Setting of cement is

Cement is one of the most important building material of the present time. It is a dirty greyish heavy powder containing calcium aluminates and silicates. The important raw materials neede for the manufacture of cement are limestone, clay and gypsum. the main step in the manufacture of cement is the heating of raw meal or slurru in the rotary kiln at a very high temperature 1400-1600^(@)C . Finally 2% or 3% gypsum is added. When cement is mixed with water and left as such for sometime, it becomes a hard mass. This is known as setting of cement. It is believed that varous aluminates and silicates present in the cement form hydrates with water which seperate in the form of gel. the gel formed start losing water partly by evaporation and partly by forming hydrates with unhydrated constituents. this results in the formation of a hard mass. Portland cement does not contain

Cement is one of the most important building material of the present time. It is a dirty greyish heavy powder containing calcium aluminates and silicates. The important raw materials neede for the manufacture of cement are limestone, clay and gypsum. the main step in the manufacture of cement is the heating of raw meal or slurru in the rotary kiln at a very high temperature 1400-1600^(@)C . Finally 2% or 3% gypsum is added. When cement is mixed with water and left as such for sometime, it becomes a hard mass. This is known as setting of cement. It is believed that varous aluminates and silicates present in the cement form hydrates with water which seperate in the form of gel. the gel formed start losing water partly by evaporation and partly by forming hydrates with unhydrated constituents. this results in the formation of a hard mass. The percentage of lime in portland cement is approximately

Cement is one of the most important building material of the present time. It is a dirty greyish heavy powder containing calcium aluminates and silicates. The important raw materials neede for the manufacture of cement are limestone, clay and gypsum. the main step in the manufacture of cement is the heating of raw meal or slurru in the rotary kiln at a very high temperature 1400-1600^(@)C . Finally 2% or 3% gypsum is added. When cement is mixed with water and left as such for sometime, it becomes a hard mass. This is known as setting of cement. It is believed that varous aluminates and silicates present in the cement form hydrates with water which seperate in the form of gel. the gel formed start losing water partly by evaporation and partly by forming hydrates with unhydrated constituents. this results in the formation of a hard mass. Gypsum is added to portland cement

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