Proctor Test on Shales

[dhooper]

One of our labs is attempting to perform a standard proctor test on a highly weathered shale material from central PA. Although the material is clearly above optimum moisture, the density is continuing to increase (even after dropping slightly on one point). Has anyone had this experience? Any ideas why this is occuring and what can be done to correct?

 

[hstanger]

Firstly has the material been oven-dried prior to testing? If so, try the test on material which is undried and wetted up to the required moisture points, then left to mature for several hours, preferably overnight. I wonder what air voids are remaining in the samples at your highest moisture content. I you find the air voids are more than 5% I would try a higher level of compaction, perhaps vibrating hammer.Obviously this will start to crush some lumps in the shale, however this is also likely to be the case in the field.