Yes you can! If you would like to know the available free water in your paste all you have to do is to know how the degree of hydration of your mix varies with time.
It is not easy process especially if you are dealing with a matrix containing admixtures. I faced a similar problem a year ago, and I solved it by modelling the degree of hydration change.
It has become appallingly obvious that our technology has exceeded our humanity
- Albert Einstein