Thank you sir for the answer.

But I have nothing do with Ca(OH)2.  I used the H(t)/HT formula for degree of hydration.

I'll send you my  excel sheet where I have done the calculations please review that and suggest me what to do. Thank you  In advance :)

How do you define the fly ash content ? What does 20% means ? Is it a replacement amount ?

I agree with the above answer. Adding fly ashes reduces the hydration rate and lowers the ultimate degree of hydration.

Check the HT value for the two cements. Is HT(OPC)>HT(PPC)? If yes, then H(t)/HT can be more for PPC since it is a ratio.

In calorimetry, there may be problem in handling initial data. You should check also initial data.