Saturation of Fly Ash

[rockstarbynight]

We are in the process of studying fly ash permeability. My problem is the saturation value. According to my reading of ASTM D5084 the hydraulic conductivity value isn't valid until you have 94% saturation or so. Based on my initial values the sample will be 45% saturated prior to being placed into the perm cell. When I check the value after saturation of at least 16 hours it will come back 38% or less. After over a week of saturation the highest value I've recorded has been in the mid-80%. I've already retubed my cells and cleaned them and with standard soils the saturations are pretty normal. Any suggestions for either a) fixing the problem or b) articles to present to my superiors on why fly ash saturation will never act in a standard fashion?

 

[euygar]

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