NCAT invites your comments and questions, which may be submitted to Christine Hall. Questions and responses are published with editing for consistency and space limitations.
Greg Sholar, Florida DOT
Are states limiting the amount of re-refined engine oil bottoms (REOBs) or banning them completely?
Oak Metcalfe, Montana DOT
How do states address sand equivalent testing, and more specifically, batching specimens for testing? Do you batch from stockpiles or cold feed? How do you address baghouse effects on the job mix formula? We don't have a state asphalt paving association in Montana, so we don't have standardized batching procedures yet; however, we will be publishing ours soon.
Oak Metcalfe, Montana DOT
How do states deal with quality assurance (QA) testing of asphalt pavements as opposed to contractor quality control (QC)? In Montana, we have a long standing internal argument about requiring QC testing from the contractor. Our solution is to craft our specifications to force QC. In reality, our contractors are using the state's QA results for their QC because "that's what they get paid on." This causes issues when test results aren't returned ASAP, if there are math errors, etc. I'm wondering if any other DOTs use this process or does everyone else keep QA and QC separate?
The following responses have been received to questions shared in the previous issue.
TDOT is considering to start fogging rumble strips. Do you fog seal rumble strips? If so, do you do anything special (strips painted over with the edgeline)? -Matthew Chandler, Tennessee DOT
Michael Stanford, Colorado DOT
Typically, CDOT does not fog their rumble strips.
Greg Sholar, Florida DOT
FDOT does not fog seal (or treat in any other way) rumble strips.
Jerry Geib, Minnesota DOT
I would always fog a rumble strip. The MnDOT special provision leaves fogging as an “option” that can be required or deleted. It’s a project by project decision.
Oak Metcalfe, Montana DOT
In Montana, we chip seal all of our new pavements, so our rumble strips get sealed during the chip seal operation; however, we are currently installing centerline rumble strips statewide for safety reasons and we have specified they be fog sealed. So, if rumble strips are ground in, either edge or centerline, and chip seal operations are more than 10 days out, we require a double shot of fog seal. If the project schedule pushes chip seal operations out to the next season, rumble strips are not to be ground until the next season so they don't go through the winter without a chip seal. For centerline rumble strips, we stripe on either side so no paint is in the hole. Edge stripes are inside the rumble strips.
Robert C. Rea, Nebraska DOT
No, but I agree that this would be beneficial for the rumble strips. The logistics of fog sealing, rumble strips, and permanent long term striping is challenging.
Eric Biehl, Ohio DOT
We have a few districts that fog seal shoulders, including rumble strips, if the rumble strips are in good shape when the mainline is either milled and filled or micro-surfaced. For high/heavy traffic routes, they typically use a mastic seal for more microtexture compared to a conventional fog seal. I do not believe we just fog seal the shoulder/rumble strip without taking care of the mainline.
What method does your DOT require for determining RAP aggregate specific gravity?
-Randy West, NCAT
Michael Stanford, Colorado DOT
CDOT requires an effective specific gravity of RAP in lieu of the RAP aggregate specific gravity. We use CP 51 (Colorado Procedure), Method B, which is Asphalt Cement Add-In for calculating the effective specific gravity for RAP.
Greg Sholar, Florida DOT
Calculating the Gsb based on other properties, Gmm, assumed absorption based on aggregate type, and asphalt content.
Jerry Geib, Minnesota DOT
The procedure is in the MnDOT lab manual. Here is the link, http://www.dot.state.mn.us/materials/manuals/laboratory/1815.pdf
Oak Metcalfe, Montana DOT
Currently, we do not specify a method. That is one of the issues we are working on. It hasn't been a critical issue up until now due to our relatively low use of RAP.
Robert C. Rea, Nebraska DOT
We use an assigned gravity to calculate volumetrics. We use burn off RAP material to perform combined aggregate specific gravity for fine aggregate angularity.
Eric Biehl, Ohio DOT
We use Gse.
Matthew Chandler, Tennessee DOT
It’s not directly calculated, as the contractor is only required to establish AC and gradation of RAP. Gse is back calculated for combined gradation of completed mix.