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Recycled Asphalt Concrete Pavement (RACP) in Bridge Embankment 4

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Jwilks

Jwilks

Civil/Environmental
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I am an entry level Civil Engineer EIT working as an inspector on a bridge. I am overseeing embankment construction and the contractor has hauled in large chunks of ODOT Item 301 Asphalt Base (3 feet in length, 1 foot thick on average) to use as fill material along with glacial till. The Ohio Department of Transportation spec book is a bit vague on the use of what I would consider "landfill material" in embankment construction. Specifically, it states that the RACP must be broken down small enough to be incorporated into 8" lifts.

My question is: What possible effect on embankment stability and quality does the use of this fill material have? I instructed the contractor to break the asphalt pieces into what I would consider within the limits of the ODOT spec. However, I'm sure that material like this has to have some effect on the mechanics of the embankment.

Thank you!
 
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Hi! VDOT does not allow the use of RAP as embankment fill. We've done research, we have our case studies, we want to use it. We may even want a further demonstration project? That said, it does lead to problems and we would require that it be reduced to some minus 2 or 3 inch dimension.

I don't have full details, but beware!

f-d

ípapß gordo ainÆt no madre flaca!
 
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In reply to your second paragraph, my experience with this kind of fill, including concrete slabs dumped, that if you run a rolling surcharge (a windrow pile of earth) 10 feet high across the final grade you can build one story stores, etc. using a 1,000 psf footing pressure and no problems later. That's for fills even 30 feet deep. However, in that you have a spec and probably a degree of compaction needed, now try to run Proctor tests and field density tests on the fill. I'd get back to your superior and let him (her) answer the question. Otherwise, say all fill has to pass a screen 6" x 6". Then there are ways to test for degree of compaction, but not ASTM or AASTO.
 
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Irrespective of some sense of strength or degree of compaction, RAP doesn't age well. Point contacts between asphalt-covered aggregates allows for creep. Water percolating through the fill furthers stripping. Hummocky ground can result - not good if you have pavement. Also not good if it's in the reinforced zone of an MSE or such.

Documenting compaction is a problem with the nuclear gauge and you cannot use the speedy for moisture content.

I think we have a research paper on this topic.

No opinion on its use in residential construction.

f-d

ípapß gordo ainÆt no madre flaca!
 
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the online spec is fairly detailed


ODOT spec said:
703.16 Suitable Materials for Embankment Construction. Natural soil, natural granular material,
granular material types, slag material, brick, shale, rock, random material, RAP, RPCC, or PCS as further defined below are suitable for use in embankment construction. The Engineer will submit samples of soils not identified from the plan subsurface investigation, from borrow sources or materials appearing questionable in the field. Furnish ACBFS according to Supplement 1027. Furnish RPCC with the reinforcing steel cut to a maximum length of 1 inch (25 mm) outside the pieces. Ensure that pieces of RAP do not exceed 4 inches (100 mm) in the largest dimension. Furnish steel slag according to 703.14. When using steel slag, RPCC, or RAP, completely blend it with at least 30 percent natural soil or natural granular material.
Click to expand...
 
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Thanks, dad. I was thinking the same thing as far as creep goes. Just judging by how easily the RACP material breaks down under dozer tracks, I kind of figured over time something similar would happen with the weight of the roadway putting pressure on the fill. Like I said, ODOT does not specifically prohibit RACP from being used as embankment fill, it simply restricts the size of the particles to be incorporated into uniformly compacted lifts. However, I was kind of sketched out when I saw the contractor hauling this material into the site.
 
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Jwilks,

It is similar to when you have imported clay. Often when its excavated from a site it comes in massive clumps. contractors just spread it and compact it quickly without breaking it up in to smaller pieces which may make it difficult to achieve compaction levels.

Good luck.
 
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apparently, the German standard is up to 10 percent RAP in embankment fill.

f-d

ípapß gordo ainÆt no madre flaca!
 
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