Manufacturing Process of Concrete - Civil Engg

Manufacture of Concrete :

I am here to Explain you in detail about Manufacturing Process of Concrete .

We all know that Concrete is used a lot for Construction.But How Concrete in Manufactured ? What Care is to be taken to Strengthen it in Future ? For all those questions like that this article can be treated as a solution. So Now Let's Jump into Process of Manufacturing of Concrete.

Depending on Quality,there are two types of concrete Good Quality Concrete and Bad Quality Concrete

Funny Thing here is that Both Good and Bad quality of Concretes are prepared using same ingredients.

Then where comes the Problem ?

The Answer is with how much care and concentration we Manufacture concrete.

Don't laugh it's not funny.What I am saying is true you must be work with utmost care and concentration preparing concrete.If not the result will be Bad Quality Concrete

There are various stages of manufacturing good quality concrete.Let's chase them down

• Batching
• Mixing
• Transporting
• Placing
• Compacting
• Curing
• Finishing

Every stage I mentioned above is important and must be proceeded with utmost care for good results.

Let us deal with them in order and believe me it is fun to learn them.

Batching :

Batching means measurement of materials for manufacture concrete correctly.

There are two ways of Batching 

1. Volume Batching
2. Weigh Batching

Volume Batching

Volume Batching means the measurement of ingredients for manufacture of concrete in volume.

Actually Weigh batching is preferred more.But for some unimportant constructions we can use Volume Batching.The reason why Volume Batching is not given importance is that it's results are not so accurate.When we measure same amount of moist sand and dry sand in volume,it gives us two different results.In this way our results misses path and gives us bad quality concrete.

Gauges used for Volume Batching are named as Farmas. 

Generally Cement is measured in weight,it is never measured in volume.One bag of Cement bag is taken as 35 liters in the case of volume batching. For one batch mix we add one bag of cement.Water is added by multiplying Water cement ratio with weight of the cement.

For example if the water cement ratio is 0.5 then 0.5x50=25 . Here 50 is weight of one cement bag.We will add 25 Kgs or 25 liters of water for the addition of one bag of cement.

Weigh Batching

Weigh Batching means the measurement of ingredients for manufacture of concrete in Wegiht.

Weigh Batching is most Preferred method.The reason is that it gives best results .Measurement of materials will be accurate in weigh Batching.

Based on the equipment used for Weigh Batching,it is divided into three categories :

1. Manual
2. Semi Automatic
3. Fully Automatic

For weigh batching ,we use weigh batching equipment which may vary in size depending on the importance of work.

For small jobs we use Manual Weigh Batching,where we weighing and batching of concrete are done manually.

In the Case of Semi Automatic Weigh Batching, we have Aggregate Bin gates opening automatically when we switch on.Gates will be closed automatically when Materials are being delivered.Here we can also see interlock which prevents charging and discharging.

In case of Fully Automatic Weigh Batching,the materials will be batched with the help of electrically equipment. We can see the complete record of weigh batching.After completion of batching we can collect it on conveyor belt below the bins.

For measurement of Water we use cans of 5 liters,2 liters,1 liter and half liter respectively.

My Sincere advice is that Prefer Weigh Batching Always.

Mixing :

Mixing of materials thoroughly is essential to obtain uniform concrete.The aim of mixing is the the concrete obtained from it must be of uniform colour, homogeneous and good consistency.

We have two methods to obtain well Mixed Concrete :

1. Hand Mixing
2. Machine Mixing

Hand Mixing :

Hand Mixing is manual and we use shovels to do so.For Simple tasks we can proceed with Hand Mixing but Machine mixing is mostly preferred for Important tasks.

In Hand Mixing first we must choose an impervious concrete or brick floor sufficient to spread one bag of cement over it.Now spread a layer of fine aggregate and then coarse aggregate over it.Now it's time to add layer of cement over it.With the help of shovel mix it dry till we can see uniform colour mixture. Now sprinkle water over it again and again till we get uniform concrete. Note that I used the word Sprinkle not Pouring . 

You can understand by reading above Paragraph why Hand Mixing is not preferred,now let's move onto Machine Mixing.

Machine Mixing :

In Machine Mixing we use Machines to mix the aggregates with cement and water.

Depending on the function of Machines,it is of two types Batch Mixers and Continuous mixers.Batch mixers produces concrete batch by batch with a time interval,coming to Continuous mixers it continuously produces concrete.Continuous mixers are used for large construction projects like construction of Dams where continuous production of concrete is required. 

For normal concrete works we use Batch mixers.Batch mixers can be pan type or Drum Type. Efficiency if mixing depends on the blades and how pan or drum revolving to mix the concrete.There are three types here Tilting,Non Tilting and Reversing.

In tilting we can see drum tilting and so that materials can be mixed well.In Non tilting no tilting is seen which results in segregation of concrete.Reversing means the drum rotated totally upside down.Non Tilting must not be preferred for good construction works.

Water must be added in sufficient quantities also here in Machine mixing we can add Plasticizers to strengthen concrete.But when we add Plasticizer we must be careful so that it doesn't effect Homogeneity of concrete.

Transporting :

Transporting of concrete must be done carefully.Bad quality concrete is obtained mostly due to Bad Transportation techniques. In most of the cases during Transportation Segregation of concrete takes place which means separation of mixture from water.Also Homogeneity of concrete obtained in mixing gets effected.

Various methods adopted for Transporting of concrete :

• Mortar Pan
• Wheel Barrow and Hand Cart
• Crane,Bucket and Rope Way
• Truck Mixers and Dumpers
• Belt Conveyors
• Chute
• Skip and hoist
• Transit Mixers
• Pump and Pump line
• Helicopters

Depending on economical conditions and importance of work we choose one of the above method to Transport Concrete. Remember that our ultimate aim during Transporting of concrete is to eliminate segregation and lost of homogeneity during the Process.

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Placing :

Batching,Mixing and Transporting properly will not give you good results if you are not careful while Placing the concrete.Placing of the concrete must be done with utmost care and in systematic manner.There are so many situations while Placing concrete,depending on those situations we must take precautions.

Various Situations of Placing of concrete are :

1. Placing concrete in Foundation
2. Placing Concrete on Slabs
3. Placing Concrete in layers within  timber and steel shutters
4. Placing concrete in columns,beams and floor
5. Placing concrete under water

Based on the situation mentioned above we will choose layout and equipment for placing concrete.Procedure must be planned before placing concrete.If we won't plan it leads to wastage of concrete.Bad Placing of concrete leads to re-construction.

While Placing Concrete Segregation i.e; separation of materials must not take place.we must inspect the form work.Most Important thing is Placing of concrete must not take time.It must be placed as soon as possible after Mixing.If you take more than 30 minutes time gap between mixing and placing,it leads to hardening of concrete which in turn effects the workability of concrete.

Keep the situation in the mind and concentrate on procedure.Give exact Timing and so that Placing of concrete in perfect.

Compaction :

Compaction is must be done after placing of concrete.

Why is it so necessary ?

The reason is that During Mixing,Transporting and Placing Air gets Entrapped in the voids of the mix.Due to this trapped air in between voids the strength of the concrete reduces a lot.

For 1% of entrapped air in between the voids strength of the concrete decreases by 6%.So to avoid decreasing strength of the concrete it is necessary to do compaction

Compaction can be done in Two ways

1. Hand Compaction
2. Compaction by Vibration

Hand Compaction :

Hand compaction is done for unimportant works.For urgent works we can use Hand compaction but to gain results it must be performed Carefully.Hand compaction is of three types as explained below :

• Rodding : Rodding is done with the help of 2 meters and  16 mm diameter rod.The rod will be poked in the edges and corners .It is done in such a way that entrapped air gets escaped.Sometimes we use bamboo,cane and iron rod too 
• Ramming: Ramming should be preferred only in case of ground floors and places where there will be no reinforcement.We must not use ramming technique in places of reinforcement as it leads to failures and disturbance in reinforcement.
• Tamping: It is mainly used for roof slabs and road pavements.It is a method in which 10cmx10cm wooden cross beam is used to do compaction.By tamping we can achieve compaction and leveling simultaneously.

Compaction by Vibration :

Hand compaction when done properly gives satisfactory results.However Strength of the concrete decreases in the case of Hand compaction.This is because Hand compaction involves high water cement ratio which in turn reduces Strength of the concrete.But if we compact by vibration low water cement ratio will be enough which imparts high strength concrete.

Also 4 cm slump is enough for Compaction by vibration where 12 cm slump required for Hand compaction.So Compaction by Vibration will be more efficient when compared to that of Hand Compaction.

Different types of Vibrators used are explained below :

• Internal Vibration: They are also called as Needle Vibrators or Immersion Vibrators.They are most commonly used.Vibrations are caused be eccentric weighs attached to the shafts.There will be a needle inside of specified length and diameter.Also it contains a power unit.For larger construction we use needle of larger diameter.
• External Vibration : External Vibration is done when Internal vibration can't be achieved.It is less efficient when compared to that of Internal Vibration.Also it consumes more power.It is mostly used in Heavily reinforced areas.
• Table Vibration: It is mostly uses in laboratories where we keep concrete over that surface.
• Platform Vibration: It is similar to that of Table vibrators but here we can work with concrete in large scale. 

Curing:

Curing is very very important to achieve best results from concrete.If Curing is not done properly it definitely gives bad results.Curing must be done in time to get good results.

Why Curing was that much Important ?

The reason is that Hydration i.e; the process of causing something to absorb water ,Hydration of concrete depends on Hydration of cement.Hydration of Cement continues for long time.It starts fast but continues for long time.Also the amount of Gel formed depends on extent of Hydration.

For Hydration we require a water cement ration of 0.23 and to fill voids in gel pores we require up to 0.15.So totally we require water cement ration about 0.38 for hydration and to fill space in gel pores.So we do curing to achieve good results from concrete.

Curing methods may be broadly divided into four categories :

• Wet Curing
• Membrane curing
• Application of Heat
• Miscellaneous 

Curing is very interesting topic and I am going to discuss about it in detail in my upcoming article.

Finishing :

Finishing is an important task after the completion of finishing.Finishing can be done in so many ways.Also before Finishing we have to do surface treatment.Smoothing is done for flatness.Also for aesthetic view we can add some materials too.Finishing "Finishing" Topic in one or two Paragraphs is not correct,I am going to work on it and write an article on it soon.Until then stay tune to u=our website.

Hope you likes Manufacturing Process of Concrete Article.If you have any queries or suggestions I will be happy to deal with them in comments.