Answered What is Maximum Flyash Content in Concrete mix design

Sumit Civil

Well-Known Member
Dec 11, 2017
968
341
India
I want to know. As per IS codes what is the maximum flyash content i can add into concrete as a replacement of Cement.

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

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

Dnyan Deshmukh

Eternal Member
Staff member
Sep 7, 2017
2,504
4,358
Pune
According to IS 1489 part 1 Portland Pozzolana Cement Specification, Fly Ash based and ammendment no 3 of july 2000.

The fly ash added in ppc should not be less than 15% and not more than 35%.

The PPC is marked as 33 grade cement (there are no specification for higher grade of cement in ppc)

According to IS code you can replace portland cement by max 35% of fly ash content.

Many people tried replacing opc with 50% or more using fly ash - it termed as high volume fly ash concrete (HVFC). Do trials of concrete mix designs before using it for actual work.
 

Dnyan Deshmukh

Eternal Member
Staff member
Sep 7, 2017
2,504
4,358
Pune
You need to understand the manufacturing process of cement.

Any PPC 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 fly ash 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 35% of fly ash

PPC will have 35% fly ash and opc 65% total will some to 100%.

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

Hope you understood.
 

Dharmesh10

Newbie
Feb 9, 2020
1
0
Bina
According to IS 1489 part 1 Portland Pozzolana Cement Specification, Fly Ash based and ammendment no 3 of july 2000.

The fly ash added in ppc should not be less than 15% and not more than 35%.

The PPC is marked as 33 grade cement (there are no specification for higher grade of cement in ppc)

According to IS code you can replace portland cement by max 35% of fly ash content.

Many people tried replacing opc with 50% or more using fly ash - it termed as high volume fly ash concrete (HVFC). Do trials of concrete mix designs before using it for actual work.
You need to understand the manufacturing process of cement.

Any PPC 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 fly ash 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 35% of fly ash

PPC will have 35% fly ash and opc 65% total will some to 100%.

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

Hope you understood.
sir,
I didn't find proportion of 15 to 35 % fa content in IS copy mentioned by you.can you please share me highlighting part of it, its very important for me ,if not here, please do reply on 7744843604..
I will be really thankful to you
 

MOHAMMED ABDUL RAFAY

Founder Member
Staff member
Sep 7, 2017
362
158
Hyderabad
You need to understand the manufacturing process of cement.

Any PPC 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 fly ash 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 35% of fly ash

PPC will have 35% fly ash and opc 65% total will some to 100%.

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

Hope you understood.
Very well explained