Free water saturation wf

Post Reply
jebjorn
WUFI User
WUFI User
Posts: 2
Joined: Thu Mar 01, 2018 6:07 am -1100

Free water saturation wf

Post by jebjorn » Thu Mar 01, 2018 6:22 am -1100

The moisture storage function is dependent on the free water saturation, w_f. However, I would like to know by what wf is determined.
I know that the maximum water content w_max is determined by the porosity of the material, but I can find nowhere by what wf is determined by. Is that also determined by porosity?

Thank you in advance.

/Johanna

Manfred Kehrer
WUFI International Support Team
WUFI International Support Team
Posts: 351
Joined: Thu Mar 10, 2005 2:17 am -1100
Location: Northbrook, IL; USA
Contact:

Re: Free water saturation wf

Post by Manfred Kehrer » Thu Mar 01, 2018 6:39 am -1100

Put the material in liquid water water until constant weight is reached. Theoretically this is when all pores are totally filled with water, which would then be the max. water content. Practically when you define water content uptake less than e.g. 0.1 mass percent a day as constant weight, that is what is a good approach for the free water saturation. ASTM C1699 can be used for it, though the 0.1% per day definition is not in there, but can be be taken from ASTM C1498.
Manfred
Wiss, Janney, Elstner Associates, Inc.
Official WUFI® Collaboration Partner for USA/Canada
Enjoy WUFI® :) .... It is easy and complex.

Thomas
WUFI Administrator
WUFI Administrator
Posts: 311
Joined: Sun Jun 19, 2005 10:33 pm -1100

Re: Free water saturation wf

Post by Thomas » Thu Mar 01, 2018 6:40 am -1100

Hi Johanna,

the free saturation is not uniquely determined by any of the other material parameters. That is, you can not simply compute it from other material data - you need to measure it.

It is mainly determined by the details of the pore structure of the material: the pore size distribution, the interconnection structure of the pores, the amount and distribution of 'blind' pores, etc. You don't know the details of these pore characteristics, and even if you knew them, no simple method is known which would allow to compute free saturation from that knowledge.

Regards,
Thomas

jebjorn
WUFI User
WUFI User
Posts: 2
Joined: Thu Mar 01, 2018 6:07 am -1100

Re: Free water saturation wf

Post by jebjorn » Tue Mar 06, 2018 12:44 am -1100

Thank you for the reply!

The intention was not to calculate it, rather to understand it so this was very helpful.

/Johanna

Post Reply