Fill RD > 100% in crusher fines

[dgillette]

Just got off the phone with a lab guy in one of our other offices. He was confused by the std. equation giving him RD over 100%, but his CALCULATIONS are obviously correct.

He reports max=104 pcf, min=92.7, and in-place=106.7. The material is crusher fines being used for pipe bedding. Don't know the lift thickness, but they are using a walk-behind roller of some sort, not something big. The material is "squeegee," crusher fines from a quartzite quarry used for concrete aggregate. This would be very angular material of course.

Is it weird to have the fill density come out higher than the lab max with small compactors, or can there be enough particle crushing in freshly crushed angular material to produce this? They ran both nukes and sand cones on the fill, and they were consistent with each other.

Have any experience with this issue? I don't.

Thanks,
Dave

 

[emmgjld]

It is possible these crusher fines may not be a candidate for the Relative Density. I know in my area, we have never had to use the RD for crusher fines. I would recommend running a Modified Proctor, ASTM D-1557, on the material to see which is higher.

 

[Ron]

Dave...agree with emm...Mod Proctor more appropriate for the material. 106.7 doesn't seem very high for the material description when compared to mod Proctor.

 

[dgillette]

From the lab tech: "the material is crusher reject material, very clean……..however the specified material was to be well graded and isn’t, so the designer has rejected use of it along with a couple of other reasons. End of problem for now."

End of problem, but not resolution of the mystery. I wouldn't have thought that even fresh crusher rejects would break down enough to explain it. He's a very experienced lab hand, so I doubt he's fouled anything up in the test procedure. If he comes up with wacky results on anything else, I'll suggest he check his max density machine. It wouldn't be the first time one got out of whack and gave erroneously low max densities.