Proctor test on recycled asphalt 1

[tipup]

My state DOT has decided to implement a density testing specification for all base course materials, including recycled asphalt on mill and re-lay jobs. I have several issues with this spec, but have serious issues with performing nuclear meter testing and Proctor tests on recycled asphalt. Does anyone out there feel that the Proctor test is not valid on recycled asphalt? Any issues with performing meter testing on recycled asphalt?

 

[Ron]

If the recycled asphalt is being combined with soil to create a stabilized base then it is possible to use a moisture-density relationship (Proctor), keeping in mind that the optimum moisture will be quite a bit lower than typical soil-aggregate mixtures, since the recycled asphalt does not absorb much moisture. If the end material is to be recycled asphalt as a graded aggregate base alone, then the moisture-density relationship will not work and another method must be used.

I would probably not rely on a Proctor test for anything above about 1/3 recycled asphalt in the mixture. Nothing magic about the 1/3, I just think that more than that inordinately throws off the moisture issue, thus making a moisture-density relationship impractical.

A modified Marshall method, similar to that used for recycled asphalt emulsion material would be a better option.

As for doing direct transmission testing in asphalt-laden material, you will have to do correlation testing to other volumetric density methods (sand cone preferably).

 

[tipup]

Thanks Ron. You echo my opinion on this. I don't know why I cant get anyone at the DOT to understand the issues with it.

 

[oldestguy]

I have the same problem to work on. This is for Wisconsin, I assume. I plan to send a complaint to the Secretary of the Department detailing why this is a very problematic form or testing.. In the past this sending to the top has done wonders.

I also question the shear strength benefits as compared to the "Standard Compaction" methods, specifically in regard to setting a structural number for pavement design.

 

[Ron]

OG- If mixed with soil, the structural number can be determined from CBR. If all recycled material, would probably have to run resilient modulus test

 

[fattdad]

This topic has me interested. I've been asking around VDOT to learn of our experiences. Maybe I'll get somewhere. . . In the meanwhule, here's some information from the FHWA:

http://www.fhwa.dot.gov/publications/research/infrastructure/pavements/97148/049.cfm

f-d

¡papá gordo ain’t no madre flaca!

 

[oldestguy]

Ron: What do you think about CBR run in place? I have an old green book (Soils Manual) from the Asphalt Institute that shows this. Looks not too hard to do. Sure would solve everything.

 

[BigH]

tipup - are you talking, too, about cold in-place recycling as well? I've had a bit of experience with it in India - I thought it worked very nicely in taking a beat up existing asphalt pavement and upgrading it to a decent base course on which new HMA would be placed. We used some cement and emulsion during the in-place milling and replacement. To check the efficacy of the newly placed "base" course, we did Benkelman beam testing. Indian Institute of Technology a few years later used a falling weight deflectometer. In any event, there was marked improvement. In this case, a performance specification would be better than a proctor - but we also did proctors as well but using techniques for cold in-place materials. For any interested, I attach the paper that was written on the particular job . . .

 

[Ron]

OG...yes, field CBR could be done, provided he can find someone with the equipment to do it. We had the equipment at Law Engineering back in the 70's, and occasionally did field CBR's, particularly on Corps of Engineers projects.

BigH....OG and I discussed this method in a side phone call on Sunday. I agree it would be something to look at. We've had good results with mix-in-place recycling to create a new base material out of existing surface and base. Just finished a remediation design on about 7 miles of pavement in Central Florida using this method. Our typical design uses a reclaimer to accomplish the pulverizing and mixing; with asphalt emulsion injected during mixing (usually about 3% emulsion by weight). Followed immediately with compaction using modified Marshall method for density standard. As soon as the emulsion "breaks", it can be driven on (usually 4 to 6 hours in our climate).

 

[fattdad]

CIP that's being discussed is consistent with our practice.

f-d

¡papá gordo ain’t no madre flaca!

 

[oldestguy]

Ron:

I question what structural number the mixed-in place old surface and some base has versus the original virgin base course. This is with the design based in part on the AASHTO Interim report from the Ottawa Road test about 1962. With Proctor tests (a research paper) showing lower max compared to original base, makes me think it might be lower. From what I can tell no added emulsion, etc. will be added.

Wisconsin used to use 14, but for some reason apparently has dropped all bases to 10. I may learn more soon however.