Question

How to determine SiO2/Na2O ratio after mixing Na2SiO3 (SiO2=30%, Na2O=9%, water=61%)and NaOH (8M)solutions?

Answer 1

Sodium metasilicate mixed with cold, concentrated sodum hydroxide yields sodium orthosilicate and water
Na2SiO3 + 2NaOH → Na4SiO4(in solution) + H2O
Now, your question. looking at mass relationships..
assume one mole of each..
122grams + 80 g>>>184g+ 18
of the 184 grams of sodium orthosilicate, one can Pull from it 124 grams of Na2O, and 60g of SiO2. That on the basis of mass, is about 2:1 ratio
Honestly, the way your question is worded, I am not certain what it is aiming for.

Answer 2

Thank you.
This mix is used in concrete technology. They mix Na2SiO3 solution and NaOH solution and add it to fly ash and aggregate to make concrete. The resulting SiO2/Na2O ratio is important for making concrete. I want to know how it is determined. I have seen somewhere they mentioned they have mixed NaOH (5 M) and Na2SiO3 (SiO2=30%, Na2O=9%, water=61%)with a Na2SiO3/NaOH ration of 1.5, and the resulting SiO2/Na2O ratio is 0.15, but they haven't mentioned how.