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Manufacturing Of Clay Bricks | Part 1 | Selection And Preparation Of Clay And Moulding | Bricks | Construction Materials | By Ashutosh Nautiyal

The manufacturing of clay bricks is carried out in a number of stages which are as follows:- Selection And Preparation Of Clay Moulding Drying Burning Selection And Preparation Of Clay:- First of all, suitable deposits of clay are first located and thoroughly tested for the quality of brick making. Then, the clay for bricks is prepared in the following order:- Unsoiling:- About 20 cm of the top layer of the soil is removed after clearing the trees and vegetation as it generally contains stones, pebbles, gravel, roots, etc. The soil used for making building bricks should be free of gravel, coarse sand( having particle size more than 2 mm), lime and kankar particles, organic matter, etc.

Manufacturing Of Clay Bricks(Part 1)





Manufacturing Of Clay Bricks | Part 1 | Selection And Preparation Of Clay And Moulding | Bricks | Construction Materials | By Ashutosh Nautiyal
Manufacturing Of Clay Bricks(Part 1)




The manufacturing of clay bricks is carried out in a number of stages which are as follows:-

  


  • Selection And Preparation Of Clay 

  • Moulding

  • Drying 

  • Burning 




Selection And Preparation Of Clay:-



First of all, suitable deposits of clay are first located and thoroughly tested for the quality of brick making. Then, the clay for bricks is prepared in the following order:-


Unsoiling:-




  • About 20 cm of the top layer of the soil is removed after clearing the trees and vegetation as it generally contains stones, pebbles, gravel, roots, etc.


  • The soil used for making building bricks should be free of gravel, coarse sand( having particle size more than 2 mm), lime and kankar particles, organic matter, etc.


Digging:-




  • After unsoiling, the proportion of additives such as fly ash, sandy loam, rice husk ash, stone dust, etc. should be spread over the plane ground surface on a volume basis.



  • The soil mass is then dug out, puddled, watered and leftover for weathering and further processing.



  • The digging operation should be done before rains.



Weathering:-




  • Stones, gravels, pebbles, roots, etc. are removed from the dug soil and it is heaped on level ground in layers of 60-120 cm.



  • This soil is left in heaps and for at least one month it is exposed to the weather if weathering is considered necessary for the soil.



  • It is done to develop homogeneity in the mass of soil, particularly if they are from different sources.



  • It is also done to eliminate the impurities which get oxidized.



  • To some extent, soluble salts in the clay also get eroded by rain which may otherwise cause scumming at the time of burning of the bricks in the kiln.



  • The soil should be turned over at least twice and it should be ensured that the entire soil is wet throughout the period of weathering.



  • Water may be sprayed in order to keep the soil wet as often as necessary.



  • By exposing the soil to weather, the strength and plasticity of the clay are improved.



Blending:-




  • To modify the composition of the soil, it is mixed with sandy-earth and calcareous-earth in suitable proportions.



  • To obtain the right consistency for moulding, a moderate amount of water is mixed to the clay.



  • The mass is mixed uniformly with spades.



  • For easy mixing and workability, the addition of water to the soil at the dumps is necessary.



  • The addition of water to the clay should be controlled in such a way that it may not create a problem in moulding and drying.



  • The size and shape of the finished brick may get affected by excessive moisture.



Tempering:-




  • Tempering consists of kneading the earth with feet so as to make the mass stiff and plastic.



  • In this stage, the clay is brought to a proper degree of hardness and it is made fit for moulding.



  • It should preferably be carried out by storing the soil in a cool place in layers of about 30 cm thickness for not less than 36 hours as it will ensure the homogeneity in the mass of clay for further processing.



  • For manufacturing good brick, tempering is done in pug mills and the operation is called pugging.






Manufacturing Of Clay Bricks(Part 1) | Selection And Preparation Of Clay | Bricks | Construction Materials | By Ashutosh Nautiyal
Pug Mill(Image From Book By S.K. Duggal)



  • Steam, diesel or electric power may be used for the pugging operation in a pug mill.



  • Blended clay along with required water, is fed into the pug from the top.



  • The knives cut through the clay and break all the lumps of clay when the shaft rotates.



  • The thoroughly pugged clay is then taken out from the opening which is provided in the side near the bottom.



  • The yield from the pug mill is about 1500 bricks.





Moulding:-




  • It is a process of giving a required shape to the brick from the prepared clay.



  • Moulding may be carried out by hand or by machines.




Manufacturing Of Clay Bricks(Part 1) | Selection And Preparation Of Clay And Moulding | Bricks | Construction Materials | By Ashutosh Nautiyal
Details Of A Mould(Image From Book By S.K. Duggal)




  • The process of moulding of bricks may be the hand moulding(soft-mud), the stiff-mud(machine moulding) or the dry-press process(moulding using a maximum of 10% water and forming bricks at higher pressure).



  • The Soft-mud process is used to make fire bricks.



  • The Dry-press method is used for making roofing, floor and wall tiles.



  • The Stiff-mud process is used for making all the structural clay products.



Types of Moulding:-



Hand moulding:-



Hand moulding is further divided into two types:-


Ground moulding:-




  • This method is adopted when a large and level land is available.



  • The ground is levelled and sand is sprinkled on it.



  • The bricks obtained from this moulding don't have a frog and their surface becomes too rough.



  • Moulding blocks or boards are used at the base of the mould to overcome these defects.



  • The process consists of shaping in hands a lump of well-pugged clay, slightly more than the size of the brick volume.



  • It is then rolled into the sand and with a jerk, it is dashed into the mould.



  • The moulder then gives blows with his fists and presses the clay properly in the corners of the mould with his thumb. 



  • The extra clay on the top surface is removed with a strike(sharp edge metal plate) or with a thin wire stretched over the mould which has to be dipped in water every time it is used.




Manufacturing Of Clay Bricks(Part 1) | Selection And Preparation Of Clay | Bricks | Construction Materials | By Ashutosh Nautiyal
Wire Strike And WoodenStrike(Image From Book By S.K. Duggal)





  • After this, the mould is given a gentle slope and is lifted leaving the brick on the ground to dry.



  • If the mould is dipped in water every time after use, such preparation of bricks is known as slope moulded bricks.



  • If fine sand or ash is sprinkled on the inside surface of the mould every time after use, such preparation of bricks is called sand moulded bricks.



Table moulding



  • The bricks are moulded on stock boards nailed on the moulding table.




Manufacturing Of Clay Bricks(Part 1) | Selection And Preparation Of Clay | Bricks | Construction Materials | By Ashutosh Nautiyal
Moulding Table(Image From Book By S.K. Duggal)





  • Stock boards have the projection for forming the frog.




Manufacturing Of Clay Bricks(Part 1) | Selection And Preparation Of Clay | Bricks | Construction Materials | By Ashutosh Nautiyal
Stock Board(Image From Book By S.K. Duggal)





  • The process of filling clay in the mould is the same as in the ground moulding process. 



  • After this, a thin board called pallet is placed over the mould.



  • The mould containing the brick is then smartly lifted off the stock board and inverted so that the moulded clay along with the mould rests on the pallet.



  • The mould is then removed in the same way as in the ground moulding and the brick is carried to the drying site.



  • The cost of brick moulding increases when table moulding is adopted.



Machine Moulding:-



Machine moulding is further divided into two types:-


Plastic Method:-




  • It is a quick and economical method.



  • The pugged, stiffer clay is forced through a rectangular opening of a brick size by means of an auger.





Manufacturing Of Clay Bricks(Part 1) | Selection And Preparation Of Clay | Bricks | Construction Materials | By Ashutosh Nautiyal
Plastic Moulding(Image From Book By S.K. Duggal)






  • Clay comes out of the opening in the form of a bar.



  • The bricks are cut by a frame which consists of several wires at a distance of brick size. 



  • These bricks are also known as wire-cut bricks.



Dry-press Method:-

  


  • The moist and powdered clay is fed into the mould on a mechanically operated press.



  • This clay in the mould is subjected to high pressure and takes the shape of bricks. 



  • The bricks obtained from this process are denser, smoother and uniform than the ordinary bricks.



  • They are burnt carefully as they are likely to crack.



  • These bricks are also known as pressed bricks.









*Self Typed
*Source- Internet, Books, Self-Analysis




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About the Author

This is Ashutosh Nautiyal. Currently, I'm pursuing my graduation from Bipin Tripathi Kumaon Institute Of Technology, Dwarahat, Almora and my branch is Civil Engineering. I have done my schooling at Omkarananda Saraswati Nilayam, Rishikesh.

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