We have conducted permeability tests on high volume fly ash specimens in triaxial by applying constant head at the top of the specimen by a back pressure system and we measured the volume of permeated water coming out of the sample at the bottom. In some specimens we couldn't observe water coming out, I suggest you to use a volume change transducer for such cases to measure the volume of infiltrated water with time and then after dismantling you can easily measure the infiltration depth by visual inspection to calculate at least the infiltration rate. Coming up to your question, you can better saturate your samples by soaking them in a vacuum dessicator well sealed and filled with water, applied vaccum pressure can be around 40-60 kPa. In this process you will see that after keeping them in the system under vacuum for 48 hours there will not be any more air bubbles coming out of the samples. You can also increase the vacuum pressure to evaluate this better. Then weight them and calculate saturation, you will see that you can reach over 90% with this method. Good luck in your research.

Eris Uygar