Although we are reducing amount of admixture 25%-20% and we are using M40 grade concreteOver vibration can cause the fine materials to get accumulate at surface and near to form face.
If overvibrated, fines on surface will going to call for shrinkage.
As from picture and shape it look like max structure area have form finish, overvibration cant be seen.
Increase the pouring rate and keep control on vibration.
Airation - admixture used in concrete generally release air in concrete, the more effect of airation seen in self compacting concretes or super fluid concretes. This is non controllable, or u can control it by changing admixture.