Can Corruption be the Reason of Frequent Power Cuts in Zirakpur!?

 In June 2020 month there was an article in Tribune which stated that electricity board, PSPL, was confident there would be no power cuts in the next four months. Here is the link: https://www.google.com/amp/s/www.tribuneindia.com/news/chandigarh/no-scheduled-power-cuts-in-zirakpur-for-4-months-100605

But on 8th august, there was a 5 hours power cut in the day and then frequent power cuts whole night. The situation has not changed because it was grim in the July month too. I wonder what are the reasons!! The article states that all the infrastructure is in good conditions after all the necessary repairs. PSPL official is promising no power cuts for the next months, in the article, but nothing has changed. 

( Above Image shows a Screenshot of a notification by PSPCL App which notified of a power cut from 9 am to 5 pm, on 10th Aug, 2020 in Zirakpur area.)

Maybe there are certain infrastructure lacks. But there can be other reasons too, maybe corruption!? It is just a wild guess, and no one individual is intended to be targetted in this article. Any names upcoming in this article is merely taken for illustration purpose only. No personal allegations are made. 

 Please let me explain. There are more than dozen of housing societies in Zirakpur, and there are hundreds of individual house connections in each of the societies. These connections are taken by individual owners who pay monthly or quarterly charges, as asked by PSPCL, to the state supplier. There are many societies maintained by the respective builders who also are the constructor of them.  Apart from the main PSPCL electricity connections there are back up connections from the generators given to the houses with their separate individual meters. Diesel generators are switched on whenever there is a main supply cut. Electric power consumed from these generators is charged from the house owners at certail profit margins.

Generally builders charge more than 18/- rupees per unit of electricity, while the cost of generation of electricity with DG is generally 16/- rupees per unit or lower. 

They definitely earn some margins on these connections. For example Leafstone Luxury Apartments on Pabhat road has 182 flats. So if an individual consumes monthly 20 units of this back up power, the back up power charges are 18×20 = 360 rupees. Total revenue from 182 flats = 182 × 360 = 65520 rupees monthly. It is just a wild guess, the amount can vary up and down.

 There are many small new builders in Zirakpur like M D Builder( constructor of Leafstone Apartments) who are treading onto the completion step of their first or 2nd project. For them even such low revenues matter a lot. 

Now let's take the guess- what if these contractors/builders bribe the electricity department executives a monthly amount of 2000 rupees each? If there are 20 such builders, the monthly amount becomes 40000/- rupees. That is a possibilty. 

To all the honest officials out there reading this article-- please think about it and act fast! These electricity cuts are everyday happenings, and instead of any improvement I have seen a year-on-year rise since lasr year. Nothing improves here in Zirakpur. It is strange how this place is so much difficult to live than our very neighbor UT Chandigarh. 

Thanks!

Garsa Stone -A Construction Material found in Kullu

Hi,
Garsa is a place near to Bajaura, Bhunter at a distance of about 8 km from Bajaura. Recently I was nearby to this place and was told about the mine, a source of the famous Garsa stone.
This stone can be extracted in the form of layers, both sides finished in a perfect manner suitable to use as the wall surfaces.
Vinod, my neighbour cum friend is the resident of the nearby village, has used this stone on the walls of his home.

Garsa Stone used on the walls of house

His home looks quite beautiful with these stone finished surfaced walls. While coming back from Bhunter to Sunder Nagar I observed a number of houses which used the same stone as a surface finish material for the walls of their houses.
I was told by Vinod that the main advantage of using this stone is that its color doesn't fade away with time, so you don't have to replace it with time. Another great advantage is its natural aesthetic appearance.

Here is the photo showing the wall finished with the Garsa Stone available only at Garsa in Kullu district of Himachal Pradesh.

Thanks for your kind visit!

Timber

Hi, How you doing?

Why Timber is obsolete these days? what are the conditions under which timber is desirable to be used?
Well, timber is one of the building materials known to the mankind. Before man realized the other materials, timber was used throughout the world as the construction material, perhaps the few of materials known to man. Today timber is used as for beams, columns, piles, roofings, bridges, trusses, doors and windows.
In places like Kashmir, where timber is available in abundance, it is widely used for almost every construction work, but now-a-days for important construction works, use of timber has become obsolete due to the following reasons:

1. Steel components are cheaper.
2. Timber components require often frequent renewal. 
3. There is often difficulty and considerable delay in securing the desired quality, sizes and lengths of timber.
4. Timber components are liable to be caught by fire. In this regard steel has the maximum advantage.

Inspite of the disadvantages listed above, there are certain conditions under which use of timber may be felt desirable. In places which always remain wet and are not liable to drying and wetting, timber piles have been found satisfactory. Regarding bridges, timber bridges involve low first cost.

Bridges are rarely constructed entirely of timber, in many cases, the compression members are made of timber and tensile members are made of steel. Such bridges are called combination bridges. 

timber trusses are also used in jobs of a temporary character- for example, false work needed for supporting workmen and materials or in some cases to support a temporary road around a site on which a permanent steel structure if being erected.

Thanks for you kind visit!

Classification of Aggregates

Hi,

Aggregates are used for the manufacturing of the concrete. Aggregates are classified into two categories according to their size:

1. Coarse Aggregates These are the aggregates which have sizes more than 4.75 mm. In laboratories they are separated as the aggregates which are retained on the BIS test sieve no. 480. Generally, broken stones are used as the coarse aggregates.
2. 
   
3. Fine Aggregates These are the aggregates which have a size less than 4.75 mm. In the laboratory, they are classified as the aggregates which pass through the BIS sieve no. 480. In general, Natural river sand is used as a fine aggregate.

Now we will discuss the characteristics of the coarse aggregates:

• As per IS:383-1963, the shape of the particles of the aggregates may be round, angular and flaky. Rounded particles do not have good interlocking, whereas irregular and angular particles show very good inter-locking properties. Rounded particles show good workability.
• They should have a rough surface to get the better bond between particles and cement paste.
• Porosity and water absorption should be less.
• Harmful ingredients such as iron pyrites, coal, mica, shale, clay, alkali and organic impurities should be avoided. These materials should not be present in such quantities that they may affect the strength and durability of the concrete. The total amount of deleterious materials in aggregates should not exceed 5%.

Thanks for visit!

Fly Ash as a Road Material

What is Fly ash?
Fly ash is a waste material obtained from the furnaces, which use the coal as a fuel for energy. Fly ash particles are spherical in shape and they fly from the plant and if not captured will pollute the surroundings. So, this is not only waste material but a pollutant.

Can we use Fly ash for useful works?
It was hoped that fly ash will make a good material because it has cementing properties when mixed with right proportions of different materials and can be used as a road material for the stabilization of the sub-grade and to replace the cement in cement concrete roads.
Tests were conducted at Civil Engineering department, NIT Hamirpur in the year 2009 by three final year students under their major project and a very big report was prepared to give you the detailed report.

How to get the report?
Well, just contact me through the email or leave a comment and I will tell you the procedure for that.

Compaction Factor Test for Fresh Concrete

Hello,

How you doing?

Here is what you searched for:

• Aim: To find out the compaction factor for the given fresh mix of concrete.

• Theory: Workability of concrete is the ability/ease with which concrete can be mixed, transported and placed. This is a major factor which contributes to the other properties of concrete also. If concrete is workable enough then it can be compacted with less compacting effort.

 So there is a relation between the amount of work required to compact a given fresh concrete and the work-ability of the concrete. This relation is well suited for the concrete of the low water cement ratio. Slump cone test is also used to find out the work-ability of the concrete but only recommended for the concrete of higher work-ability. For less workable concrete(having less water cement ratio), compaction is standardized by various standards. 

• Apparatus: Compaction factor apparatus/machine, weighing balance, cow/mixing tray.

Compaction Factor apparatus

• Procedure:

1. Oil the inner sides of the top and bottom cone frustum.

2. Prepare a M15 concrete mix(1:2:4) using a water content of about 0.4-0.6 by weight of cement.

3. Fill the top cone frustum with the fresh mix of concrete and then open the gate and let the concrete fall on the second frustum.

4. Open the gate of second frustum and let it fall on the cylinder to fill up to top of cylinder. 

5. Measure the weight of the cylinder filled with the concrete(partially compacted) and then empty this.

6. Again fill the cylinder with the same sample of the concrete but this time, do the compaction using the mechanical vibrator to do the compaction. 

7. Again measure the weight of the cylinder filled with the concrete(Fully compacted).

8. Clean all the apparatus and put them at their places as before.

• Calculations: 

Let weight of the empty cylinder = W1

Let weight of the cylinder with the partially compacted concrete = W2

Let weight of the fully compacted(Using mechanical vibrator) concrete with cylinder = W3

Compaction Factor = Weight of the partially compacted concrete/ Weight of the fully compacted concrete

i.e., Compaction factor = (W2-W1)/(W3-W1)

• Result: The compaction factor of the given fresh concrete mix is .....

(Note: Relation between the compaction factor and work-ability is that higher the compaction factor higher is the work-ability. Theoretical maximum value of the compaction factor can be 0.96 to 1.0)

Thanks for visit!

  

Please contribute to improve this article!

Concrete Slump Test

Aim: 

To determine the slump of a given fresh concrete mix sample.

Theory:

 Work-ability is the ease with which the given concrete mix can be mixed together, transported to the application place and can be placed/applied/compacted their within the initial setting time of cement. This property depends largely on the amount of water added i.e. water cement ratio of the concrete mix and kind of aggregates used. Generally work-ability increases with the addition of the water, however it results in the less strength of concrete. So we have to settle for an intermediate value of water cement ratio at which it may have the sufficient work-ability as well as sufficient strength.

Apparatus: 

Slump cone apparatus, cow tray

Slump Cone Apparatus:
This is the standard apparatus used to determine the slump of the  given fresh concrete. This is a metallic, conical shaped, of height 30 cm, 20 cm, and 10 cm as the larger and smaller diameters respectively at the far two ends. This is provided with two handles to lift it above the base.
Cow tray: This is used to mix the given materials in the given proportions (Water, Cement, Sand and coarse aggregates).

Procedure: 

•  Oil the inner side of the slump cone apparatus(so that concrete do not stick to its sides)  and put it on the table/floor with the larger diameter base at bottom. 
• After mixing the concrete,fill the slump cone with the freshly prepared concrete mix, compacting this in 3 layers, each layers tamped with the tamping rod giving 25 no. of blow. 
• Remove the extra concrete overflowing from the top edge of the cone with the help of a strike.
• Hold the two handles of the cone in hand and then lift the cone up leaving the concrete on the base. 
• After the cone support is removed, concrete will fall under its own weight. The initial height of the concrete cone was 30 cm and after the fall, you have to measure the amount of fall from its top with the help of a scale.

Calculations: 

Initial height of the concrete = 30 cm
     Height after lifting the cone = h2.
 slump = 30 - h2 (cm)

Interpretations of Results: 

Types of slumps

• Slump of concrete is interpreted as collapse slump, shear slump and true slump. 
• If it is collapse slump then the concrete is too wet, and shear slump also indicates a poor mix, concrete of true slump is of value. 
• A concrete of slump value 0 to 25 mm is used in the road mixes, 10-40 mm mixes are used in the foundations with light reinforcement, and 50-90 mm used for normal concrete works compacted with vibrations, slumps .10 cm are considered of higher work-ability.

Thank you!

  

Le-Chatelier's Apparatus- Soundness Test of Cement

Hello,

• Aim: To find out the Soundness of Cement.
• Apparatus: Le- Ch-atelier's Apparatus, Weighing balance, measuring cylinder, trowel, mixing pans heater, thermometer.
• Standard Reference:  Test is performed as per IS: 4031 (Part - 1) - 1988,

• Theory: 

Cement of good quality does not contain the impurities like free lime, magnesia and sulphates, so this should be checked before use.

When it contains the impurities named above, it can expand after reacted with the water, which will result in the unwanted results like, cracking, unwanted expansion of the dimensions and lower strength. 

Le-Ch-atelier's Apparatus is the standard apparatus prescribed as per IS:5514 -1969 to check the presence of the impurities in cement.  Cement is said to be sound when the expansion is below 10 mm.

• Procedure: 

Prepare a cement paste of 78% of standard consistency of the cement, and fill it into the split brass cylinder.

Cover the top and bottom of the cylinder and put it in water at 27 degrees Celsius for 24 hours.

After 24 hours, measure the separation between the two indicators at their pointed ends.

Then heat the whole water and immersed cylinder with paste up to a boiling temperature in 30-35 minutes and then boiling  for 3 hours.

After cooling it down, again measure the separation between the two pointers.

• Calculations: 

Let the reading before putting the cement paste into the boiling temperature  = L1

                         After three hours of hot water immersion = L2

                  Expansion = L2-L1

• Result: As the value of expansion is (Less/More)..... than 10 mm so the cement is .........(Sound/Unsound).

Thanks for visit!

  

Please give your reviews and thereby help in improving the article.

Tensile strength of Cement - Briquette Mould Test

Hi,

• Briquette's mould machine is an apparatus which is used to form the briquettes of the cement mortar which are used to find out the tensile strength of the cement. 

These briquettes are of standard dimensions are constructed by pouring in the fresh cement mortar into the briquette mould and then followed by required curing.

• After the curing, these mortar briquettes are tested for the amount of tensile load they can bear before getting failed. This load is the tensile strength of the cement. You have to test more than 3 briquettes, some suggest 6 nos. of them to get the desired results. Average of these results is taken as the final value.

Thanks!

Relevant Books:

  

BIS: 712 -1984 Classification of Lime

Hello,

How you doing? Okay, so here is what you searched for:

Introduction- Lime as a cementing material:

Lime has been used as a cementing material since the ancient times  in India and abroad. Ancient Egyptians and Romans used this material for various constructional processes. Even in India, various engineering structures like palaces, bridges, temples etc were constructed with lime mortar and still are in shape.

After the invention of cement in 1824 lime has been replaced by the cement to a large extent, however it is still used at certain places, like for the repairing of the structures which were originally built with the lime mortar and at the places where lime is freely available and cement has its acute shortage.

• Classification of Lime:

Broadly lime is classified into three categories:

(1) Fat Lime   (2) Hydraulic lime  (3) Poor Lime

(1) Fat Lime/Pure Lime:-  Fat lime is also known as pure lime, white lime or rich lime, this is manufactured using the purest form of the limestone. It is popular with its name as fat lime since its volume is increased to about 2 to 2.5 times its originally volume after getting slaked. It slakes vigorously.

(2) Hydraulic Lime: This lime has the hydraulic property, means it can set under the water also. It contains clay and some amount of ferrous oxide also. This is also known as water lime.Depending upon the amount of clay hydraulic lime is classified into further three categories:

(a) Feebly hydraulic lime

(b) Moderately hydraulic lime

(c) Eminently hydraulic lime

Increase in the percentage of clay makes the slaking difficult and thus increases the hydraulic property of lime. With about 30 per cent of clay lime resembles the color of cement.

The color of fat lime is not white therefore fat lime looks more sanitary than the hydraulic lime.

(3) Poor Lime: Poor lime contains more than 30 percent of clay therefore it is also known as impure lime. It slakes very slowly and also does not dissolve into water. It has poor binding property and its color is muddy white.

This lime forms very poor mortar and so such lime can be used for inferior types of work or at places where good lime is not available.

BIS: 712 - 1984 classifies lime under six categories, namely Class A, Class B, Class C, Class D, Class E and Class F.

Class A lime is used for structural purposes because it is eminently hydraulic lime and has the property of setting even in the absence of air. It has to be supplies in the hydraulic form only. Its minimum strength with lime sand mortar of proportion(1:3) by weight at the end of 14 days and 28 days should be respectively 1.75 N/mm2  and 2.80 N/mm2.

Class B lime is the semi-hydraulic lime which is used for mortars for masonry and it can be supplied either as quick lime or as hydrated lime. Its minimum compressive strength with lime sand mortar of proportion(1:3) by weight at the end of 14 days and 28 days should be respectively 1.25 N/mm2 and 1.75 N/mm2.

Class C lime is the fat lime which is used mainly for finishing coat in plastering, whitewashing and with suitable admixture such as surkhi or any other pozzolanic material to produce artificial hydraulic mortars. It is to be supplied in hydraulic or quick form.

Class D lime is the magnesium or dolomitic lime which is used for finishing coat in plastering, whitewashing, etc. It is to be supplied in the hydrated or quick form.

Class E lime is the kankar lime and is used for the masonry works, it is to be supplied in the hydraulic form only.

Class F  lime is also known as Siliceous dolomitic lime which is used for undercoat and finishing coat of plaster. It is to be supplied in the hydrated or quick form.

Thanks for visit!

  

Please contribute to improve this article.

Vicat's Apparatus - Consistency and Setting Time of Cement

Hello There,

How you doing? Well go for what you looking for:

• Vicat's Apparatus 

is used to find out the consistency, initial setting time and final setting time of the cement. In the normal consistency test we have to find out the amount of water to be added to the cement to form a cement paste of normal consistency.

 Vicat's apparatus consists of an arrangement to hold the plunger of 10 mm diameter and two other needles which are made to freely fall into a mould filled with the cement paste and the amount of penetration of the needles of plunder can can be noted using the vertical graduations from 0 mm to 50 mm.

•   Consistency Test: 

To find out the consistency test you have to take a sample of dried cement of about 400 g weight which must pass through the 90 micron IS Sieve. Then mix in it about 25% of  water by weight a form a uniform paste withing 2 minutes of time.

 Fill the Vicat's mould with this paste and make the 10 mm plunger fixed to the arrangement to just touch the top surface of the cement paste. Make it freely fall and note the amount of penetration.

When the penetration is of about 42 to 45 mm or when the reading on the vertical graduation is about 5mm to 7mm that means cement is of normal consistency. Generally the water required to form a paste of normal consistency is 30%.

Vicat's Apparatus with all the accessories

• Initial Setting Time: 

Initial time of Cement is the time required by the cement for its early setting. Cement must be applied to the place of its use before its initial setting so it is necessary to find out the initial setting time that is available with us.

Vicat's apparatus is the standard apparatus used to find out this initial setting time. Look in the figure above, there is a needle of diameter 1 mm. This needle is fixed to the movable rod weight.

The cement paste of normal consistency is formed and is filled in the mould. Now the needle is made just touch the top surface of the cement paste and made freely fall in it. Initial setting time is the time from the mixing of the cement and the water to the time when the penetration of the needle is just above 5 mm from the bottom of the base plate or mold.

Generally the initial setting time of the ordinary Portland cement is 30 minutes. For Slow setting cement this time may be increased by adding the admixtures or Gypsum up to 60 minutes.

Similarly, for the final setting time we have to use the third needle which has a enlarged  5mm hollow cylindrical base. The final setting time is the time from the mixing of the water to the time when this needle just makes the impression on the surface of the cement but do not penetrate into it. Generally the final setting time of cement (OPC) is 10 hrs to 12 hrs.

 

Photograph of the Vicat's Apparatus

Thanks for visit!

  

Wet process - Cement manufacturing -Flow Diagram

Helllo,

Cement manufacturing is done in the following three major processes:
(a) Mixing
(b) Burning
(c) Grinding

(a) Mixing: Mixing can be done in two ways: (1) dry method and    (2) wet method.
Dry method was used in the early periods in between 1913 to 1982. After 1982 all the cement manufacturing plants in India are equipped with the technologies of Dry process, since this is more energy efficient and environment friendly method of cement manufacturing. In this post I am sharing with you the flow diagram of the wet process of the mixing because it is in the syllabus of the many Diploma courses.

Wet Process - Manufacturing of Cement

Thanks for visiting!


  

Functions of various Constituents of Cement

Functions of various cement ingredients:

•      Lime (CaO) :This is the important ingredient of cement and its proportion is to be carefully maintained.  The lime in excess makes the cement unsound and cause the expansion and disintegration of the cement. On the other hand if the lime is deficient it will decrease the strength of the cement and will cause it to set quickly.
•  Silica (SiO2) :   This is an important ingredient of the cement as it imparts strength to the cement due to formation of di-          calcium silicate and tri-calcium silicate. If silica is present in excess quantity its setting time is prolonged          however strength is increased.
•  Alumina (Al2O3) :      This ingredient imparts quick setting property  to the cement. It acts as a flux and it lowers the clinkering        temperature. However the high temperature is essential for the formation of a suitable type of cement and       hence in alumina should not be present in excess amount as it weakens cement.
• Calcium Sulphate (CaSO4) :This ingredient is in the form of gypsum and its function is to increase the initial setting time of cement.
• Iron Oxide (Fe2O3) :This imparts color, hardness and strength to the cement.
• Magnesia (MgO) :This ingredient, if present in small amount, imparts hardness and color to the cement. A high content of magnesia makes the cement unsound.
• Sulphur(S) :A very small amount of sulphur is useful in making sound cement. If it is in excess, it causes cement to become unsound.
• Alkalies :The most of the alkalies present in raw materials are carried away by the flue gases during heating and the cement contains only a small amount of alkalies. If they are in excess in cement, they cause a number of troubles such as alkali-aggregate reaction, efflorescence and staining when used in concrete, brickwork or masonry mortar.

Harmful Constituents of Cement:

The presence of the following two oxides adversely affects the quality of cement:
        1) Alkali Oxides K2O and Na2O    2)    Magnesium oxide MgO.

    If the amount of alkali oxides exceeds 1 per cent, it leads to the failure of concrete made from that cement.     Similarly, if the content of magnesium oxide exceeds 5 per cent, it causes cracks after mortar or concrete        hardens. It is due to the fact that magnesium oxide, burned at a temperature of about 1500 degree            Celsius, slakes very slowly, when mixed with water.

Reference:


  

Bricks Classification and Specification (IS-1077:1992)

Hi,

According to Indian standard(IS: 1077: 1992) bricks are classified into the following categories:

Classes of common burnt clay bricks:

       Class Designation             Average compressive strength not less than[ (N/mm^2) (kg/cm2)

1. 35                                               35            350
2. 30                                              30                300
3. 25                                              25             250
4. 20                                              20                200
5. 17.5                                           17.5          175
6. 15                                              15                150
7. 12.5                                           12.5              125
8. 10                                               10                100
9. 7.5                                              7.5               75
10.  5                                                5                   50
11.  3.5                                            3.5                35

General Quality

• Bricks shall be hand moulded or machine moulded and shall be made from suitable soils. They shall be from from cracks and flaws and nodules of free lime. 
• Bricks with height of 90 mm or 70 mm will be moulded with a frog of  10 mm to 20 mm deep on one of its flat sides. Bricks with height of 40 mm or less, and as well those made by extrusion process  may not be provided with frogs.
• The bricks shall have smooth rectangular faces with sharp corners and shall be uniform in colour

.For other detailed dimensions and tolerance criteria please visit the IS 1072 : 1992

In some books the classification of the bricks is given as below:

General classification:

(1) First Class Bricks

(2) Second Class Bricks

(3) Third Class Bricks

First class bricks: 

Specifications: 

(1) Plain surface, sharp edges and size with tolerance in dimensions +-3%

(2) Uniform red or brownish colored.

(3) High crushing strength, not less than 10.7 N/mm2

(4) Machine moulded

(5) Efflorescence- NIL

(6) Water absorption less than 15%.

USE: They are used for the exterior wall brick works, short columns and arches.

Second class bricks:

Specifications:

(1) Slightly uneven faces and edges with tolerance in dimensions +-8%

(2) Uniform colored but may be slightly over burnt.

(3) High crushing strength, not less than 7 N/mm2

(4) Hand moulded

(5) Efflorescence- Little

(6) Water absorption less than 20%.

USE: They are used for internal walls and compound walls.

Third class bricks:

Specifications:

(1) May be distorted with blunt edges.

(2) Over burnt or under burnt and non uniform color.

(3) High crushing strength, not less than 3.5N/mm2

(4) Hand moulded

(5) Efflorescence- Large

(6) Water absorption less than 25%.

USES: They are used for flooring, paving, small brick foundations and brick bat lime concrete(B.B.L.C.).

Relevant books:   

  

Drying, Burning of Bricks- Bull's Trench Kiln, Hoffman's kiln

Hello!

The Manufacturing of bricks is consists of  following processes:

1.  Preparation of brick clay
2.  Moulding of Bricks
3.  Drying
4. Burning of bricks

First two operations are already discussed in the previous two parts of the article in the same blog. In this blog I am going to discuss with you the Drying and the Burning of the bricks:

• Drying Of Bricks: 

Drying of the bricks at lower temperature is done to strengthen the bricks to have sufficient strength so that they do not crack or crumble while holding and carrying them in hand.

Finally bricks are to be stacked in the kiln, but they must possess the sufficient strength to maintain their shape while the transportation and loading operations, so drying of the bricks is important process. Drying of the bricks can be done in two ways:

(a) Natural Drying: Natural drying is done by putting the bricks in the under the air circulation, generally avoided to direct Sun-light.

(b) Artificial Drying: In artificial burning bricks are put under a temperature of about 120 degrees Celsius in a tunnel like structure where arrangements are there to maintain the temperature.

 These tunnel kilns can be period or continuous. In periodic kilns the bricks are dried periodically but in the continuous they are put continuously at one end and dried bricks are taken out at the other end.

• Burning of Bricks: 

Bricks are burned at high temperature to gain the strength, durability, density and red color appearance.

All the water is removed at the temperature of 650 degrees but they are burnt at an temperature of about 1100 degrees because the fusing of sand and lime takes place at this temperature and chemical bonding takes between these materials after the temperature is cooled down resulting in the hard and dense mass.

 Bricks are not burnt above this temperature because it will result in the melting of the bricks and will result in a distorted shape and a very hard mass when cooled which will not be workable while brickwork. Bricks can be burnt using the following methods:

(a) Clamp Burning

(b) Kiln Burning

•   Clamp Burning: 

Clamp is a temporary structure generally constructed over the ground with a height of about 4 to 6 m. It is employed when the demand of the bricks is lower scale and when it is not a monsoon season.

 This is generally trapezoidal in plan whose shorter edge among the parallel sides is below the ground and then the surface raising constantly at about 15 degrees to reach the other parallel edge over the ground.

 A vertical brick and mud wall is constructed at the lower edge to support the stack of the brick. First layer of fuel is laid as the bottom most layer with the coal, wood and other locally available material like cow dung and husk.

Another layer of about 4 to 5 rows of bricks is laid and then again a fuel layer is laid over it. The thickness of the fuel layer goes on with the height of the clamp.

After these alternate layers of the bricks and fuel the top surface is covered with the mud so as to preserve the heat.

Fire is ignited at the bottom, once fire is started it is kept under fire by itself for one or two months and same time period is needed for the cooling of the bricks. 

• Disadvantages of Clamp burning: 

1. Bricks at the bottom are over-burnt while at the top are under-burnt. 
2. Bricks loose their shape, and reason may be their descending downward once the fuel layer is burnt.
3. This method can not employed for the manufacturing of large number of bricks and it is costly in terms of fuel because large amount of heat is wasted.
4.  It can not be employed in monsoon season.

• Kiln Burning: 

Kiln is a large oven used for the burning of bricks. Generally coal and other locally available materials like wood, cow dung etc can be used as fuel. They are of two types:

(a) Intermittent  Kilns.

(b) Continuous Kilns.

• Intermittent Kilns 

are also the periodic kind of kilns, because in such kilns only one process can take place at one time. Various major processes which takes place in the kilns are:

Loading, unloading, Cooling, and Burning of bricks.

There are two kind of intermittent kilns:

(i) Up-draught Intermittent Kilns

(ii) Down draught Intermittent Kilns

Down draught kilns are more efficient because the heat is utilized more by moving the hot gases in the larger area of the kiln. In up draught kilns the hot gases are released after they rise up to chimney entrance.

• Continuous Kilns: 

These kilns are called continuous because all the processes of loading, unloading, cooling,  Heating, pre-heating take place simultaneously. They are used when the bricks are demanded in larger scale and in short time. Bricks burning is completed in one day, so it is a fast method of burning.

There are two well known continuous kilns:

• Bull's Trench Kiln: 

Bull's trench kiln consist of a rectangular, circular or oval plan shape. They are constructed below the ground level by excavating a trench of the required width for the given capacity of brick manufacturing.

This Trench is divided generally in 12 chambers so that 2 numbers of cycles of brick burning can take place at the same time for the larger production of the bricks. Or it may happen that one cycle is carried out at one time in all the 12 chambers by using a single process in the 2-3 chambers at the same time.

The structure is under-ground so the heat is conserved to a large extent so it is more efficient.  Once fire is started it constantly travels from one chamber to the other chamber, while other operations like loading, unloading, cooling, burning and preheating taking place simultaneously.

Such kilns are generally constructed to have a manufacturing capacity of about 20,000 bricks per day. The drawback of this kiln is that there is not a permanent roof, so it is not easy to manufacture the bricks in the monsoon seasons.

• Hoffman's Kiln:

The main difference between the Bull's trench kiln and the Hoffman kilns are:

1.  Hoffman's kiln is an over the ground structure while Bull's Trench Kiln is an underground structure.
2. Hoffman's kiln have a permanent roof while Bull's trench Kiln do not have so it former can be used in 12 months a year to manufacture bricks but later is stopped in the monsoon season.

coutesy: http://www.llanymynech.org.uk/html/hoffman_kiln.html

Layout Plan

Hoffman's kiln is generally circular in plan, and is constructed over the ground. The whole structure is divided into the 12 chambers and all the processes takes place simultaneously like in Bull's trench Kiln.

Thanks for visit!