Ebrahim,

Here is the procedure of increasing water content after compaction:

-Find an appropriate mold (maybe plastic pipe for cylinder or wood made for cubic)

-Start with an initial water content which matches with saturation ratio and  dry density target .

- Compact your sample till calculated height (still you are not on your targeted water content)

- Calculate target water content on the wet side of optimum density and matches with saturation ratio-dry density and pour half of it on the top. let it be isolated for 1-3 days depending on your soil type. ours was cohesive clay and we kept it for 2.5 days.

- Reverse the sample and pour other half of water on the bottom. Keep it isolated for the same time.

- Now your sample is almost homogeneous in water content percentages. 

-Run a water content test from top, bottom and middle of every sample after you ran your test as a report.

* you may see some error according to change in height, expansion, non homogeneous distribution and ...  You have to verify them with measuring height after reaching water content as well as water content tests.

Normally we use to saturate soil column (collected in a metallic cylinder and sealing the bottom with filter paper or cloth) in a water tray (refer attached fig). Wonder if the same would be of any help in this case. Else the set up may be improved, for example putting in an appropriate chamber and fitting with a vacuum pump etc.

Hello Ebrahim

Well uniformity of distribution is totally dependent on the amount of effort you put into mixing.

as you well know compacted soil in omc has maximum dry density so if you add more water you won't get that and the moisture content wont be optimum anymore, put that aside and assuming this is not of the importance.

based on proctor compaction standard's procedure you should add water based on soil's preliminary  dry unit weight and after the compaction took place, in the next step you must first of all remove soil from mold and in-compacted it by hammer or something like that, after that add 5 percent more water  in your case, and by using spatula, yes you're reading correctly by spatula you must mix material properly to get uniform water content through, so that's gonna take time

I don't know if there is a standard and not inventive apparatus to add water and mix it by absolute precision to reach required goal but  one thing I am sure of is that this is how we and lots of geo-labs do it

If you have any question please feel free to ask me

Best of luck

Ebrahim,

I don't know how you could add a controlled amount of water and distribute evenly AFTER compaction unless you were happy to completely saturate the sample.  If your aim is to test the sample at 15% MC but at a density that reflects the 'aggregate density' at your 10% OMC, then I can only suggest the following:

- Determine the density at OMC (10%).

- Then calculate the mass of material that filled your mold at that density.

- Add the extra mass to account for the extra 5% MC.

- Compact until the adjusted/required mass of material (at 15% MC) fills the mold to give you a density that is consistent (but greater for the extra 5% MC) to the original 10% OMC sample.

- Test as proposed.

This requires a compaction method that can apply whatever effort is necessary to achieve the target density.  You will need more compactive effort to achieve equivalent 'aggregate density' when the MC is not OMC.  I believe the gyratory compactor has the ability to 'compact to height' which may allow this to occur.  Whether that suits your test is another matter.  I previously used gyratory compaction to a 'target density' with cement treated base course.

It would be better to compact at OMC and then add the extra moisture but I can not see how this could be down with uniform moisture distribution.

Cheers,

Greg

Ebrahim,

Here is the procedure of increasing water content after compaction:

-Find an appropriate mold (maybe plastic pipe for cylinder or wood made for cubic)

-Start with an initial water content which matches with saturation ratio and  dry density target .

- Compact your sample till calculated height (still you are not on your targeted water content)

- Calculate target water content on the wet side of optimum density and matches with saturation ratio-dry density and pour half of it on the top. let it be isolated for 1-3 days depending on your soil type. ours was cohesive clay and we kept it for 2.5 days.

- Reverse the sample and pour other half of water on the bottom. Keep it isolated for the same time.

- Now your sample is almost homogeneous in water content percentages. 

-Run a water content test from top, bottom and middle of every sample after you ran your test as a report.

* you may see some error according to change in height, expansion, non homogeneous distribution and ...  You have to verify them with measuring height after reaching water content as well as water content tests.

Dear Greg,

Thank you for your response. That was really eye-opening.

As you mentioned the main difficulty is to compact the specimen at OMC and then change its moisture to some level higher or lower than the OMC. At first, I am going to approach to adding water content procedure. I know that decreasing water content to some level lower than OMC with uniform moisture distribution in specimen is another issue that I have to take into account.

I appreciate your considerations.

Kind regards,

Ebrahim