% Saturation in Expansion Index Test (ASTM 4829)

[cme45]

As of 2008, the % saturation must be 48-52% to be considered a legitimate test as per ASTM, as they no longer allow the use of a correction factor. The % saturation equation has basically two (2) variables (excluding SG), % moisture & dry unit weight. Aside from running a proctor (=extra time & $ to client), or just being plain lucky, how does one determine the correct moisture content that a given sample needs to be at in order to achieve the correct %saturation of 48-52%?

 

[FixedEarth]

I have always targeted between 50% to 60% Try lumping the sieved soil into a fist and see if it "lloks like" it is just under optimum moisture content, if so, you are in that narrow range. Curing the sample overnight always helps.

 

[cme45]

This is normally how we do it as well. However, this method is no longer practical (for us) due to the tighter constraints imposed by ASTM. The 48-52% saturation has forced us to sometimes conduct 3-4 trials before we get it right. Since each test requires a min. soak time of @ least 24 hrs, what once took 1 day, now can take 3 or 4!