When formulating concrete containing inert (non-reactive) fines with dimensions of less than 80 µm, should they be taken into account when calculating the water/binder ratio and the dosage of superplasticizing admixture?
In my opinion and experience, As you said, inert fines are intrinsic part of binder (Not added apart, like somehow would be treated as aggregate) , you must consider w/cement as = w/binder ratio for the hole cementitious material . Ex. W/(C+p) >"Cement + puzolan).