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.
Don Watson, NCAT
With the development of the regressed air void concept, balanced mix designs, and greater emphasis on higher field densities, the asphalt pavement community seems to be more comfortable with mixes designed to have less than the 4.0% air void target traditionally used for Superpave design. What is the minimum air void level for in-place compacted pavements at which the mix would not be acceptable for your organization?
The following responses have been received to questions shared in the previous issue.
What is your agency policy or specification regarding re-refined engine oil bottoms (REOB)? Are there limitations on the amount allowed, or are they banned completely? -Greg Sholar, Florida DOT
Michael Stanford, Colorado DOT
702.01 of CDOT's Specification states "Asphalt Cement shall not contain any used oils that have not been re-refined." Beyond that, the AC must meet our specifications.
Bryan Engstrom, Massachusetts DOT
REOBs are completely banned in Massachusetts.
Eric Biehl, Ohio DOT
Per ODOT Construction and Material Specification 702.02, we allow up to 5.0% previously used material (REOB, etc.) but it must be approved by ODOT. No such material has been approved to date.
Cliff Selkinghaus, South Carolina DOT
We allow it but it must be disclosed in the supplier’s QC plan. We do not use anything softer than a PG 64-22, so we have not seen any show up thus far. We also ask the suppliers to ensure their binders are compatible with any other additives like anti strips.
Matthew Chandler, Tennessee DOT
We do not have a specification requirement with regard to REOBs. We are assuming at -22 (low PG grade) there is little need to use them. We are actively utilizing an FTIR to fingerprint binders and analyze for heavy metals to identify if they are being used.
Howard J. Anderson, Utah DOT
We don't have any suppliers currently using REOB that we know of. We don't prohibit its use. According to our binder suppliers, the DTT test has limited its use in our state.
Joe DeVol, Washington State DOT
Washington State DOT does not have any policies or specifications that deal with REOBs in our asphalt binders.
How do states address sand equivalent testing, and more specifically, batching specimens for testing? Do you batch from individual stockpiles or blends from 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
Michael Stanford, Colorado DOT
Sand equivalent testing is only required for fine aggregate used for concrete. The minimum SE, as tested in accordance with Colorado Procedure 37, shall be 80 unless otherwise specified. We typically batch cold feed. Baghouse effects are addressed on the job mix formula in the D/A requirements.
Greg Sholar, Florida DOT
We rarely test for sand equivalent anymore except for proficiency samples. However, in the earlier years of Superpave implementation, we tested every sand source used in mixtures. Those samples came from stockpiles.
Bryan Engstrom, Massachusetts DOT
MassDOT annually tests source samples from stockpiles in the beginning of the year. Currently, we do not perform any SE testing during production unless a question arises.
Eric Biehl, Ohio DOT
We only require sand equivalent testing for micro surfacing. We use fines to asphalt ratio to control dust in asphalt mixtures, which also handles baghouse effects.
Matthew Chandler, Tennessee DOT
We don’t regularly use sand equivalency for HMA but do check it for micro surface. Mix design specimens are batches from stockpiles. Completed batch designs are extracted and gradations within tolerance are checked to verify that extra fines aren’t excessive.
Howard J. Anderson, Utah DOT
We take our acceptance tests from behind the paver for HMA. For SMA and OGFC we take the samples from the trucks at the hot plant.
Joe DeVol, Washington State DOT
Our SE samples are taken directly from contractor's stockpiles. We do not address the effects of baghouse fines on the JMF; the contractor is required to meet the JMF as approved on the mix design.
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? -Oak Metcalfe, Montana DOT
Michael Stanford, Colorado DOT
CDOT keeps QA and QC separate.
Greg Sholar, Florida DOT
In the early 2000s, we adopted a system where payment is based on verified QC tests. There are several layers of checking involved, but in short, FDOT tests a random split sample of the QC sample on a frequency of one FDOT test per four QC tests. If the QC test is verified, then payment is based on QC test results. If it isn't verified, then it gets a little bit more complicated and there isn't enough space here to explain. In addition, each district lab performs independent verification testing to assess the quality of the material. Prior to this approach, FDOT used to operate like Montana, where FDOT's test was used for payment, and we had the same sentiments from contractors.
Bryan Engstrom, Massachusetts DOT
We have a QA specification (Section 450) that requires both DOT acceptance testing and Contractor QC. Based on project tonnage, QC results may also be used as part of acceptance. QC results are required to be reported within 24 hours of testing in order to be used in payment determination.
Eric Biehl, Ohio DOT
Ohio requires contractors to perform QC much more frequently than we do QA. QC testing is required at least once every half-day. We will typically test one of the splits (if not more) at a frequency of 1 in 4 production days. Depending on the acceptance, there are more samples taken. We do deduct or remove and replace if the contractor has poor QC results or if there are comparison issues.
Cliff Selkinghaus, South Carolina DOT
Our QA samples are the same as the contractor’s QC samples; the only significant difference is that our QA staff witnesses the sampling and testing from start to finish. Split samples of the QA samples are later tested by the department (compare favorably: yes/no) and the technician is checked off the list being a system based approach and not every project.
Matthew Chandler, Tennessee DOT
Each year, we require the asphalt plant to submit a QC plan with stated frequencies for testing. Most of this is left up to the contractor to define, but key checks are given at the required frequency, which includes them checking the tests we run for acceptance (AC% and gradations). Additionally, we have an inspector at the plant that runs independent acceptance testing in the contractor’s lab.
Howard J. Anderson, Utah DOT
We require the contractor to submit their QC testing in any dispute resolution process. If the contractor does not do QC testing, they can't dispute any of our acceptance tests. We keep QC and QA tests separate.
Joe DeVol, Washington State DOT
WSDOT does not require contractor QC; we expect our contractors to perform their own QC rather than use our results for that purpose.