Help - Maximum Dry Density for Oversize Particles 1

[DScintille]

I am familiar with ASTM D-4718 (Correcting MDD with Oversize Particles). We have a soil sample that is coming up with a MDD of 142+ pcf with the rock correction. This seems a little high for the silty sand with gravel that we are using.

I remember in my intern days using a manual substitution of the oversize particles to get the corrected MDD without using the formulas outlined in D-4718. The method essentially allows the substitution of an equivalent weight of fine gravel (+#4 to -3/4") for the oversize rock (+3/4"). However, I don't have a source for the method.

Has anyone ever heard of this procedure? If you have, do you have a reference?

Any help is much appreciated.

 

[Ron]

The manual substitution method can be found in an older version of ASTM D1557 or AASHTO T180. Check a version that appeared before 1990.

 

[TopSoil]

Yes, I have used this method for determining the CBR value and/or the standard proctor method. There is some arguement over the validity of the useage, as it would alter your representation of the sample. however, by using a rock correction you are also making an assumption of the validity of the calculation. One of the sources of errors in determining the corrected maximum dry density (CMDD) and the corrected optimum moisture content (COMC) is the assumed moisture content of the oversized rock. Some engineers assume between 1 and 3%, so ususally use 2%. You could try looking up VTM-8 on VDOT's website. I'll look when I get to the office also.