# (#8233) Procedure to calculate the total percentage of cement replaced with fly ash

Query

Please let us know the detailed procedure to calculate the total percentage of cement replaced with fly ash by weight. Further please let us know whether submitting the batch mix report and purchase order along with specification of fly ash content would be enough or not?

Solution

There can be 3 cases of mixing fly ash in concrete:

Case 1- OPC plus fly ash -  In this case, the total quantity of OPC and Fly Ash has to be calculated. Then, percentage of cement replaced is the quantity of fly ash divided by the total quantity. For example-

Quantity of cement in kg = X

Quantity of fly ash in kg = Y

Percentage of cement replaced = [Y/(X+Y)] x 100%

Documents required: Batch mix report of each grade of concrete

Case 2- PPC only - In this case, the percentage of cement replaced is equal to the percentage of fly ash in that PPC. It is usually mentioned on the bag of PPC. If not, then ask for a test certificate from the manufacturer highlighting the fly ash percentage in that PPC.

Documents required: Batch mix report and design mix report of each grade of concrete. Test certificate of PPC highlighting fly ash percentage. If concrete is being mixed on site, then purchase order of fly ash is also required.

Case 3- PPC plus additional fly ash in concrete mix - Similar to case 1, here too the total quantity of fly ash and cement has to be calculated, and the percentage of cement replaced is the quantity of fly ash divided by total quantity. However, while calculating quantity of fly ash we have to consider both the quantities, i.e., the quantity of fly ash in PPC plus additional fly ash added while batching. For example-

If in a batch of concrete, you are using 50 kg PPC (containing 10 kg fly ash) and 5 kg additional fly ash.

Then quantity of fly ash = 10 + 5 = 15 kg

Total quantity of cementitious material = 50 + 5 = 55 kg

Percentage of cement replaced = [15/55] x 100%

Documents required: Batch mix report and design mix report of each grade of concrete. Test certificate of PPC highlighting fly ash percentage. If concrete is being mixed on site, then purchase order of fly ash is also required.