Why the proportions of M 30 and above grade of concrete are not given in is 456
- Thread starter Shubham Gomare
- Start date
Dnyan Deshmukh
Staff member
Because not every pain killer will give relif from pain but higher dosage without understanding the severity can lead to death.
Same way, a common person in india can make concrete for there home without going to Engineer or Designer.
If he or she really want to build a long lasting beutiful durable structure then i know they wont take normal pain killer or not even take a risk of taking overdose on their own.
Hope you understood my words.
I tries to explain in very common language which is understandable even by peoples who are not really an engineer.
Same way, a common person in india can make concrete for there home without going to Engineer or Designer.
If he or she really want to build a long lasting beutiful durable structure then i know they wont take normal pain killer or not even take a risk of taking overdose on their own.
Hope you understood my words.
I tries to explain in very common language which is understandable even by peoples who are not really an engineer.
Dnyan Deshmukh
Staff member
Whatever Proportions mention in IS code for each grade for doing volume batching of concrete are very generalize and have more factor of safety.
It tries to ensure, when you produce concrete with proportions stated in any part of India, if you does concrete accordingly, you will able to achieve the desired characteristic of concrete.
There are lot of advancement happened in Concrete Technology.
Structures are becoming thinner, heavily reinforced etc.
If we do follow the basic guidelines provided by IS code for doing concrete, we may able to produce concrete which can achieve ts strength properties but if you look at Today's Labour force, you will come to know that, they cant place that concrete in position and there are many reasons for it such as;
No labour will compact or place concrete which is having slump of 70 to 100 mm.
If you go in any Construction Project other that Road Concrete, you will find that workability is set to more than 150 mm - because it almost become flowable, easy to handle and placeable in congested reinforce areas and requires less compaction effort.
Now if you try to achieve such slump with conventional mixes - you will spoil all the properties of it and most probably kill the life of concrete.
If you take a look at IS code table which specifies the workability values for different types of concrete placing. - Do one thing, produce concrete with that slump value and try to pour it in structure - obviously you need to take lot of extra efforts and need to do just impossible job.
Does IS code state wrong things - no, IS code state everything TRUE and which applicable to all over INDIA.
What defines the strength of concert - below line states in understandable language.
If Water Cement Ration Increases, Concrete strength decreases and vice a versa.
So as you go for higher grades of concrete, your water cement ration need to go as low as possible.
As you reduce the water cement ration, workability of the concrete goes down.
To tackle this issue Admixtures are added in concrete which changes the desired property of concrete - in this case it changes the workablity by allowing reduction in water.
Admixtures are manufactured as per the desired properties and can be tweak at any time as per need - there is nothing specific in it that IS code says you put x amount of this and y amount of that.
If you call any admixture company, they will first take all data from you such as type of cement, brand, grade etc. aggregates source, type of water and your mixing equipment, retention time required and there are lot more parameter.
Why they do that, because after understanding your need, they will make formulation of admixture and will give you sample for making trials.
base on trial result either you approve that admixture or you will ask manufacturer to tweak some properties.
So as you go higher and higher for concrete grades, there are other materials introduce in it which are called admixture which may be chemical or powder form or other solid materials which tweaks the properties of concrete produced with them.
If IS Code do provide such information - it may not be valid for all location or some people will start objecting that, it wont work or simply does not understand what to do with that.
When we make a cycle at home we know what are the part of it and how we can make it.
but if you need to create a motor bike, here calculations are involve and there are many things which need to look in depth to ensure economical, stable, durable and best product is made for the market price.
Its same like, if you are not going to make a complicated structure or you are doing a say home project - You can utilize the information given for Conventional concrete mixes - It will give you desired result but may not be economical. it may not matter if its economical or not when your project is small or concrete produced is of very less concrete.
If the project have huge amount of concrete requirement, obviously no owner of such project is dumb to keep on producing conventional concretes by hand or small machine mixing. they will setup a big concrete producing plant at project or simply will buy from a RMC manufacturer.
Every Big Project should be economical for running and making profits out of it, say i made a small house of 1000 sft and selling it for crores of rupees - are you going to buy it - obviously not.
As every construction process is fine tuned to make economical process (some people may understand it as a cost cutting), Concrete is also part of it as it eats up lot of money of owner to produce and placing it in structure.
To make concrete affordable, someone need to do research in it which we call it as concrete mix design.
What happens in concrete mix design - concrete is designed with whatever available material at your place and making balance of it.
So to achieve higher strength - you need to reduce water - water reducing admixture can do that.
To make concrete to gain more workablility without addition of water - Plasticizer admixture can do that.
You want to gain more time for placing and compaction of admixture - retarders can help here
You want to change the viscosity of concrete - viscosity modifying admixture can do that.
when you go to higher grades, you also need to control the hydration process to ensure no cracking and damages - admixture like flyash, GGBFS, rice husk, metakolin etc will help to do that.
You want to get early results - micro silica, accelarating admixtures can do that.
and there are many many such things which need to be considered during concrete mix design.
So when you state Conventional M25 mix - it does not specify anything - it simply says under normal condition do that.
When you say its Mix Design Recipe of M25 - this is engineered concrete and have lot more other property which are added to suit that particular project environment need.
There are many more things to describe why not more than M30 is stated in IS code or why Concrete mix design to be done, if i keep on writing, there will be no end to it.
So this is another short answer for your question in somewhat technical terms which is giving you some insight of concrete designs to understand it.
Hope now your concepts are somewhat clear on it.
It tries to ensure, when you produce concrete with proportions stated in any part of India, if you does concrete accordingly, you will able to achieve the desired characteristic of concrete.
There are lot of advancement happened in Concrete Technology.
Structures are becoming thinner, heavily reinforced etc.
If we do follow the basic guidelines provided by IS code for doing concrete, we may able to produce concrete which can achieve ts strength properties but if you look at Today's Labour force, you will come to know that, they cant place that concrete in position and there are many reasons for it such as;
No labour will compact or place concrete which is having slump of 70 to 100 mm.
If you go in any Construction Project other that Road Concrete, you will find that workability is set to more than 150 mm - because it almost become flowable, easy to handle and placeable in congested reinforce areas and requires less compaction effort.
Now if you try to achieve such slump with conventional mixes - you will spoil all the properties of it and most probably kill the life of concrete.
If you take a look at IS code table which specifies the workability values for different types of concrete placing. - Do one thing, produce concrete with that slump value and try to pour it in structure - obviously you need to take lot of extra efforts and need to do just impossible job.
Does IS code state wrong things - no, IS code state everything TRUE and which applicable to all over INDIA.
What defines the strength of concert - below line states in understandable language.
If Water Cement Ration Increases, Concrete strength decreases and vice a versa.
So as you go for higher grades of concrete, your water cement ration need to go as low as possible.
As you reduce the water cement ration, workability of the concrete goes down.
To tackle this issue Admixtures are added in concrete which changes the desired property of concrete - in this case it changes the workablity by allowing reduction in water.
Admixtures are manufactured as per the desired properties and can be tweak at any time as per need - there is nothing specific in it that IS code says you put x amount of this and y amount of that.
If you call any admixture company, they will first take all data from you such as type of cement, brand, grade etc. aggregates source, type of water and your mixing equipment, retention time required and there are lot more parameter.
Why they do that, because after understanding your need, they will make formulation of admixture and will give you sample for making trials.
base on trial result either you approve that admixture or you will ask manufacturer to tweak some properties.
So as you go higher and higher for concrete grades, there are other materials introduce in it which are called admixture which may be chemical or powder form or other solid materials which tweaks the properties of concrete produced with them.
If IS Code do provide such information - it may not be valid for all location or some people will start objecting that, it wont work or simply does not understand what to do with that.
When we make a cycle at home we know what are the part of it and how we can make it.
but if you need to create a motor bike, here calculations are involve and there are many things which need to look in depth to ensure economical, stable, durable and best product is made for the market price.
Its same like, if you are not going to make a complicated structure or you are doing a say home project - You can utilize the information given for Conventional concrete mixes - It will give you desired result but may not be economical. it may not matter if its economical or not when your project is small or concrete produced is of very less concrete.
If the project have huge amount of concrete requirement, obviously no owner of such project is dumb to keep on producing conventional concretes by hand or small machine mixing. they will setup a big concrete producing plant at project or simply will buy from a RMC manufacturer.
Every Big Project should be economical for running and making profits out of it, say i made a small house of 1000 sft and selling it for crores of rupees - are you going to buy it - obviously not.
As every construction process is fine tuned to make economical process (some people may understand it as a cost cutting), Concrete is also part of it as it eats up lot of money of owner to produce and placing it in structure.
To make concrete affordable, someone need to do research in it which we call it as concrete mix design.
What happens in concrete mix design - concrete is designed with whatever available material at your place and making balance of it.
So to achieve higher strength - you need to reduce water - water reducing admixture can do that.
To make concrete to gain more workablility without addition of water - Plasticizer admixture can do that.
You want to gain more time for placing and compaction of admixture - retarders can help here
You want to change the viscosity of concrete - viscosity modifying admixture can do that.
when you go to higher grades, you also need to control the hydration process to ensure no cracking and damages - admixture like flyash, GGBFS, rice husk, metakolin etc will help to do that.
You want to get early results - micro silica, accelarating admixtures can do that.
and there are many many such things which need to be considered during concrete mix design.
So when you state Conventional M25 mix - it does not specify anything - it simply says under normal condition do that.
When you say its Mix Design Recipe of M25 - this is engineered concrete and have lot more other property which are added to suit that particular project environment need.
There are many more things to describe why not more than M30 is stated in IS code or why Concrete mix design to be done, if i keep on writing, there will be no end to it.
So this is another short answer for your question in somewhat technical terms which is giving you some insight of concrete designs to understand it.
Hope now your concepts are somewhat clear on it.
Suma
Newbie
Similar threads
