There are guidelines for your doubt, in IS 1489-1. Normally, in industry, concrete testing lab perform these tests regularly, and establish the strength gain curve for a particular brand of cement (PPC) and compare with OPC (base line data). This issue has serious repurcations on stripping time of formwork. Many incidents are noticed, when early stripping led to collapse of the members. Thus, users should be extremely cautious, to avoid, cascading / catastrophic failcures at site. In institute / college, there is no serious concerns, except for learning purposes.

As per IS 1489, part 1 as mentioned by shri Prabhakar Gundlapalli average compressive strength of cement motor cubes is 22MPa. We are using concrete made by RAMCO PPC cement and the 7 days strength is above 22 MPa..

The strength gain of concrete depends on various factors, including the mix design, curing conditions, and the type of cement used. M35 grade concrete typically indicates a characteristic compressive strength of 35 megapascals (MPa) at 28 days of curing. However, predicting the exact strength gain after 7 days for concrete with Portland Pozzolana Cement (PPC) can be challenging without specific details about the mix proportions, water-cement ratio, curing conditions, and other relevant factors. PPC contains pozzolanic materials such as fly ash, which can contribute to the long-term strength of concrete, but the early strength gain might be slower compared to concrete with Ordinary Portland Cement (OPC). In general, concrete strength tends to increase with time, and the rate of strength gain is influenced by factors like temperature, humidity, and curing methods. To get a more accurate estimation of the strength gain after 7 days, it's advisable to refer to the mix design provided by the concrete supplier or conduct laboratory tests on samples from your specific concrete mix. Testing the actual concrete you are using under the specific conditions it will be exposed to is the most reliable way to determine its early-age strength.