Classification of cement - learn Civil

Classification of cement

INTRODUCTION:
Cement is broadly described as material having adhesive and cohesive property with capacity to bond the material like stone, bricks, building blocks etc. Cement is a binder, a substance that sets and hardens independently, and can bind other materials together.

Cements are inorganic material that shows the cementing properties of setting and hardening when mixed with water. Cement is used for structural construction like buildings, roads, bridges, dam etc. The most important use is the production of mortar and concrete the bonding of natural or artificial aggregates to form a strong building material that is durable in the face of normal environmental effects. Both cement and concrete are different, because the term cement refers to the material used to bind the aggregate materials of concrete. Concrete is a combination of a cement and aggregate.  

Classification of cement:

Based on source of cement:
1. Natural cement
2. Artificial cement


1. Natural cement:

Cement is obtained by burning and crushing of 20-40% clay, carbonate of lime and small
amount of magnesium carbonate. It is brown in colour and best variety known as Roman cement,
The natural cement resembles very costly element hydraulic lime and sets very quickly and strongly
as compare to artificial cement. It finds very limited application.


2. Artificial cement:

Artificial cement is obtained by burning of calcareous mixture at very high temperature. Mixture
of ingredients should be intimate and they should be in correct proportion. Calcined product is known as Clinker.

A small quantity of gypsum added to clinker and pulverized to fine powder is
known as cement or ordinary cement or normal setting cement. After setting, this cement closely a variety of sandstone which is found in abundance in Portland in UK. Therefore, it is also known as
Portland cement.
Classification of cement
The basic components of cement

Based on broad sense cement:

1. Natural cement
2 Puzzolana cement
3. Slag cement
4. Portland cement

1. Natural cement:

It is prepared from naturally occurring lime stone by heating it to a high temperature and subsequently pulverizing It.During heating both siliceous and calcareous material are oxidized and
combine  to give calcium silicates and calcium aluminates.   

                    

 2. Puzzolana cement:

It is the material which when mixed with lime without heating gives hydraulic cement. They mainly contains silicates of aluminum, iron and calcium natural Puzzolana which is found in deposits of volcanic ash consist of glassy material and simple mixing and grinding gives the cement. Similarly slaked lime also gives Puzzolana cement but they are the cement of ancient time and at present hardly used.


3. Slag cement:

It is made by mixing blast furnace slag and hydrated lime. Furnace slag largely contains silicates of calcium and aluminum which is granulated by pouring it into cold water. Later it is dried
and mixed with hydrated lime and the mixture is finally powdered to increase the rate of setting.
Accelerator like clay, salt or caustic soda may be added.

4. Portland cement:

It is refine powder of calcined product of clay and lime stone. It has controlled composition. It is named after the paste of cement with water which resembled in colour and hardness to the Portland stone.


PROPERTIES OF CEMENT:


Following are the important properties of good cement:
1. It gives strength to the masonry.
2. It is easily workable.
3. It offers good resistance to moisture.
4. It is an excellent binding material.
5. It possesses a good plasticity.
6. It hardens early.


CEMENT AND LIME:

1. The cement can be used under conditions and circumstances which are not favorable for
lime.
2. The cement, when converted into paste form, sets quickly.
3. The colours of cement and lime are different,
4. When water is added to the cement, no heat is produced and there is no slaking action.


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