WHAT IS CEMENT , TYPES OF CEMENT , MEJAR PROBLEMS TO THE CEMENT INDUSTRY AND PRODUCING AREAS

Cement is a primary material used in modern building construction.  Cement is mainly a mixture of calcium silicate and aluminate compounds, which are composed of calcium oxide, silica, aluminum oxide and iron oxide.

                                             

To make cement, a mixture of limestone and clay is burnt at high temperature in a furnace and then the resulting clinker is mixed with gypsum and finely powdered in this process.  The product obtained is called (OPC)Ordinary Portland Cement .

                                                             

OPC (ordinary portland cement) Apart from this, many other types of cement are also produced and most of them are for special purposes, for example sulfate resistant cement, white cement, oil-well cement, etc.  They are also accompanied by some general purpose cement, and the most common of these is Pozolana Portland Cement (P.P.C.). 

                                                            

Pozolana Portland Cement (P.P.C.):-

Pozzolana is essentially a siliceous material that has no cementitious properties but in the presence of water it reacts with calcium hydroxide at normal temperatures to form compounds that have cementative properties.

Pozolana, used in the manufacture of Portland pozolana cement, can be natural like shale (gray stone), tufts, volcanic ash, pumiceites, and diatomic soil.  Clay calcination-processed substances and fly ash are also used in the manufacture of pozzolana cement.

Portland Pozolana Cement is manufactured either by fine grinding of cement cement khangar, pozolana and gypsum together or by blending Portland cement and pozolana powder evenly and thoroughly. 

                                                              

Grade(category):-

In India, O.P.C.  The construction is basically in three grades. Grades-33, Grades-43 

and Grades-53, these numbers indicate its compressive strength achieved after 28 

days, when tested in a prescribed procedure. 

                                                        

Different types of cement:-

1. Ordinary portland cement (O.P.C.):

It is the most common type of cement that is used extensively.  It has good 

resistance to cracking and dry shrinkage but less resistance to chemical attack.  

OPC is not suitable for construction work which is exposed to sulfates in soil. 

2. Rapid Hardening cement :

Rapid hardening cement Rapid Hardening cement is similar to ordinary Portland 

cement (OPC).  The initial strength is achieved by adding excessive C3S to the 

mixture and reducing the C2S content in the cement.  As the name itself is, such 

cement is used where high strength is required.  

At 3 days of age, the strength of Rapid Hardening cement is similar to the strength 

of 7 days of ordinary Portland cement.  This requires a water-cement ratio similar to

 the OPC.  This type of cement is not used for large-scale concrete construction. 

3. High alumina cement :    

This type of cement has a rich alumina content of 35%, which helps to achieve 

ultimate high strength within a short period.  This type of cement is used where a 

structure is subject to the action of seawater, chemical plants and furnaces. 

4. Low heat portland cement :

This type of cement is manufactured by reducing C3S content and increasing C2S 

content.  It has a lower compactive strength than ordinary Portland cement. It has a

 lower lime content than OPC. This type of cement is mostly used in building 

retaining walls and is not strictly suitable for thin concrete structures. 

5. Sulphate resisting portland cement :

 It is manufactured by maintaining a percentage of C3a below 5%.  This type of 

cement is used where the structure is prone to severe sulfate attacks such as soil, 

marine conditions, installation of sewage treatment tanks.

6. Air-entraining cement :

This type of cement is generally manufactured by adding 0.025–0.1% air-acting 

agents to the Portland cement clinker.  Air entering agents are usually made of 

wood resins, calcium agents, vegetable oils, and animal fats.

7. Pozzolana cement :

Pozzolana is a material that causes volcanic eruptions.  It is a smooth material in 

about 80% of soil.  Pozzolana Cement is manufactured by mixing 30% of Pozzolana

 for common Portland cement clinkers.  This type of cement is used in the 

construction of dams and weirs.

8. Expansive cement :

This type of cement is manufactured by adding stabilizer which stabilizes the cement

 to expand.  This can be achieved by adding 8–20% sulfolamunate and 15% of 

stabilizer to the ordinary Portland cement clinker.

9. White cement :

Such cement is obtained by reducing the iron oxide content in common Portland 

cement.  Strength and durability are similar to OPC.  This type of cement is used to 

engage in tiles and other interior works.

10. Oil-well cement :

To extract oil from stratified sedimentary rocks, oil wells are dug to greater depths.  

The extracted oil is poured from the steel casing for safe pumping.  It seems that if 

oil is struck, oil or gas can escape from the space between the rock formation and 

the steel cover.  Oil well cement is used to fill this space.  Oil well cement is

 manufactured by adding retarders (starch or cellular products) to common Portland 

cement.

Major problems & issues related to the cement industry :-

1. In many states, the cement industry has been damaged due to energy crisis.

2. The cement industry requires more capital investment.  There is a decrease in 
     investment by capitalists due to the relatively low economic benefits from the 

     industry.

3. The cement industry has a high energy requirement. Currently, sustainable 

    development is being emphasized.  Making and reduction of greenhouse gases 

     is a major challenge before the cement industry. 

4. Using carbon storage and storage related technologies will emerge as a major 

    issue in future.

5. In addition, promoting renewable energy use and reducing carbon emissions are 

    major challenges.

                                                         

Major cement producing areas:-

1. Gujarat:  Okha, Porbandar, Dwarka, Vadodara, Bhavnagar etc.

2. Andhra Pradesh:  Krishna, Karimnagar, Vijayawada, Gundur, Kurnal etc.

3. Rajasthan:  Sawai Madhopur, Lakheri, Chilor, Udaipur, Sirohi etc.

4. Madhya Pradesh and Chhattisgarh: Satna, Kaimur, Katni, Gopal Nagar, Durg, 

    Zabad, New Village etc.

Apart from this, cement is also produced in states like Tamil Nadu, Karnataka, Uttar 

Pradesh etc. 

BY SHIVAM DWIVEDI :