What is Maximum Flyash Content in Concrete mix design

[Sumit Civil]

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]

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.

 

[Sumit Civil]

The specifications are for manufacturing of cement.

% shown by you is of what?

How i can use this for replacement of cement.

 

[Dnyan Deshmukh]

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]

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

 

[MAR]

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

 

[Mech42]

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, For OPC-53 what are the Maximum Fly Ash content can be used?

 

[G SREENIVASA ARAO]

What is the Maximum percentage of GGBS we replaced with cement?

 

[Rehman]

As per IS code 455, amendment 4th May2000, GGBC added in concrete should not be lessthan 25% and should not be more than 70% of total cementitious.

 

[Sanchit]

Dear
As per Site research fly ash has been used in concrete at levels ranging from 15% to 25% by mass of the cementitious material component. The actual amount used varies widely depending on the application, the properties of the fly ash, specification limits, and the geographic location and climate as well .

 

[Supratic Gupta]

a. IS456 mentions that beyond 35%, is not considered as cementitious when we are talking of minimum cement
b. Why design concrete with minimum power, cement should be minumum and powder should be high.
c. Fly ash doesnot replacement doesnot provide equal strength. To maintain strength, refer to efficiency factor method developed
in research under me.

M5 with expected strength of 33.6 > 31.6 MPa,
Water Cem FA Total Powder Min powder FA%
170 340 0 340 340 0%
170 298 53 350 350 15%
170 291 97 388 388 25%
170 286 154 440 440 35%
170 279 229 508 279/0.65=429 45%
155 255 208 463 255/0.65 = 392 45%

All will provide equal strength and acceptable M25 design.

With design strength going up, higher fly ash % become impossible, so M30 onwards
35% is realistically correct max fly ash. But with M25, M20, M15 and M10, we have
have higher FA%

eg. M10 target strength = 15.8 Let us assme we design for 18MPa

Water Cem FA Total Powder Min powder
170 180 220 400 276 55%
155 164 201 365 252 55%
170 171 317 488 262 65%
155 156 289 445 239 65%

for M10, non structural concrete - Mild exposure is 220 and 240 moderate , all these mix designs are acceptable.