Answered What is maximum content of GGBS in concrete mix design

I want to know. As per IS codes what is the maximum GGBS content i can add into concrete as a replacement of Cement.

Can i add GGBS beyond the limit specified in IS code.

This is important interview question, i want correct answer for it.
 
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Dnyan Deshmukh

Staff member
As per IS 455 portland slag cement specification and as per ammendment no 4 of May 2000.

In PSC cement manufacturing, GGBS added should not be less than 25% and should not be more than 70%

Compressive strength of Portland Slag Cement should not be less than 33 Mpa, means PSC available in 33 grade (there are no specification for higher grades of PSC)

So according to IS code you can replace portland cement up to 70% by using GGBS.

You may try replacing cement by more than 70% and share your experiance.
 
As per IS 455 portland slag cement specification and as per ammendment no 4 of May 2000.

In PSC cement manufacturing, GGBS added should not be less than 25% and should not be more than 70%

Compressive strength of Portland Slag Cement should not be less than 33 Mpa, means PSC available in 33 grade (there are no specification for higher grades of PSC)

So according to IS code you can replace portland cement up to 70% by using GGBS.

You may try replacing cement by more than 70% and share your experiance.
The specifications are for manufacturing of cement.

% shown by you is of what?

How i can use this for replacement of cement.
 
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Dnyan Deshmukh

Staff member
You need to understand the manufacturing process of cement.


Any PSC is blended cement - what it mean.


After formation of clinker, it is grinded with gypsum in ball mill to achieve required fineness and uniform mixing and grinding.


During this process GGBS is added into it as per % and grinded with clinker and gypsum. After grinding it is stored in silo and then sent for delivery through bag packs or in bulker as loose cement.


% denotes the percentage of total quantity of cement.


Example blending it with 70% of GGBS


PSC will have 70% GGBS and opc 30% total will some to 100%.


When we say % replacement, it is always of total volume.


Hope you understood.