This is the Summer 2014 edition of the quarterly BINDER TECHNICIAN NEWS brought to you by the Asphalt Institute.

Ask Mike

Michael T. Beavin
Technical Training Coordinator
Asphalt Institute

Question: My question regards DSR PAV testing. This test is the “limiting factor” for us – if our asphalt batch is going to fail it will fail the PAV DSR and I will have acceptable results on everything else. As you know, a result of less than or equal to 5000 kPa passes this test. Usually if we fail, we fail well above the 5000 kPa cutoff, so both of my results are over 5000 and the batch fails and needs to be reblended. I had a batch last week where my first result was 5021 (fail) and my second result was 4673 (pass). These results aren’t as close to each other as I usually run, but are within the repeatability of the test. Because I didn’t think I could average a failing result + a passing result, I ran a third test and got a result of 4939. Would the correct approach be to average the first two result (fail + pass), or average all three results (fail + pass + pass).  I have no reason to believe that any of these tests were outliers that I could eliminate. I read through both D7175 and T315 and couldn’t find this addressed, so is there a different ASTM method that deals with this sort of situation?  (I looked at ASTM E178 and ASTM D3244, but neither of them seemed to address this exact situation.) I know that ideally we shouldn’t be running up so close to the max spec (given the reproducibility of this test an outside lab could easily fail this product) but some of those circumstances are out of my control. I just wanted to know how to handle this situation and data correctly if this situation arises in the future so I can address it in our lab SOP. 
Thanks so much,

A concerned lab tech
Answer: Thanks for your question. After consulting with AMRL, Dr. Dave Anderson and Mike Anderson, AI Director of Research, the consensus is this is a tough one! Good question! Let’s start with test replicates. The ASTM and AASHTO DSR standards do not require DSR testing in replicate but I understand why you would want to do this given the borderline results you have been seeing. So what to do? You have two results (or three). You have passing and failing results. Do you pick a result and report it or do you average the results and hope the average passes the parameter? According to Dr. Anderson “If two results are within acceptable limits according to the precision and bias estimate, averaging would be appropriate. Averaging three results would be even better.” There is no guidance in the standards to do this, however, so commonly a passing retest is the one that is reported. Kind of like ‘fail and there must have been some mistake so retest. Pass and pat yourself on the back for a job well done!’ Be careful, though! That same material is likely going to be tested again in the agency lab and, given the increased variability for multilaboratory testing, they are just as likely to get a failing result as a passing one. Even with that possibility, most labs would breathe a sigh of relief and report the passing one.
Long story longer I hate to say that I’m not going to be able to provide you with a definitive answer but you have certainly restarted an interesting conversation. Way to stir that pot! In my conversation with AMRL, they said it’s a complicated issue and that the answer can change depending on the scope of testing and which side of the sample you are on. Additionally, tests on some materials, soils tests for example, have inherently low variability. In these cases it’s easy. Test fails – that’s it. But the M-320 tests have higher variability. As variability increases, confidence in the test results decreases (I could preach about NBTC certification again here, but I won’t). So, I don’t have a cut and dry answer for you but I do have a few thoughts:

There is no requirement for replicate tests in M-320 but it couldn’t hurt to continue this practice for the PAV DSR as long as you are seeing borderline results. For added confidence, the more replicates the better.
There is a precedent for handling passing and failing values, ASTM D3244 Standard Practice for Utilization of Test Data to Determine Conformance with Specification. I would think that you could use this standard as a basis for averaging your results.
The industry standard for BBR testing is to test a set of two beams and average the results. It is not uncommon for the m value to pass on one beam and fail on the other but have the average of the two save the day. This is interesting given that the BBR has much less variability than the DSR. We are suspicious of the test with an acceptable range of 6.8% multilaboratory variability and trusting of the one with 40.2%. Hmmmmm…
The most common way to approach borderline passing and failing DSR test results is to report the passing one. Do this at your own risk because the agency lab won’t be so forgiving.
Someone please draft a standard that clarifies this!!
Thank you for the question and we challenge our readers to chime in on this topic! Lets find an A for the Q.

Submit your binder question to Mike Beavin and if it is chosen for an edition of Binder Technician News, you will receive a FREE custom t-shirt or hat. Please include your t-shirt size in your email.
NBTC A National Standard

• The Uniform CPA Examination protects the public interest by helping to ensure that only QUALIFIED individuals become licensed as U.S. Certified Public Accountants.

• An electrician becomes licensed only after taking an exam to DEMONSTRATE knowledge of the National Electrical Code and local electrical and building codes.

• By passing two intensive COMPETENCY exams and earning a license from their state’s licensure board, an engineer can add P.E. to their title.

Nearly every job that generates goods and services that are vital to the public has an accompanying certification. A standard certification. These exams help increase confidence in the product and decrease the cost associated with poor performance.

• Asphalt binder technicians produce data crucial to the acceptance of materials and the ability to catch bad data before it is reported has a direct impact on deadlines and bottom lines. There is little incentive for these technicians to pursue certification…we ask you to help us change that.

• Certified Technicians generate reproduceable test results according to the test standard. They are the professionals you want performing your material tests.

The asphalt binder portion of the North East Transportation Training and Certification Program was expanded nationwide in 2008 in the form of the National Binder Technician Certification (NBTC), creating a standard, national program. The NBTC program is fully endorsed by AMRL. The number of certified binder technicians is growing. Now the Asphalt Institute is asking for your help on the state level. The potential benefits of technicians certified under a STANDARD program can only be realized as more and more states buy into the concept that qualified = certified.

There are 42 states with NBTC-certified technicians. This is a great start, but you can help us finish the job by pushing that number to fifty. Our ultimate goal is to see at least one certified technician in every binder lab that produces acceptance-testing data. You can help us achieve that goal by promoting the program in your state.

- Mike Beavin



Brought to you by the letter "Q"

As in Q-tip! No, this is not a lesson in hygiene, or an episode of Sesame Street, this unsung hero of the lab has many different uses and there are many labs out there that for one reason or another are not using them.

The cotton swab’s most common use at the Asphalt Institute is in trimming the DSR. While many labs use bulky paper towels to clean up the excess binder after a trim, the swab method has proven to be faster, cleaner and more effective.

The Q-tip is also very helpful in cleaning up the DSR after completion of the test. The small surface areas of the DSR plates, along with the nooks and crannies of the design, can make it tough to get it thoroughly clean. Be sure to get the wood handled swabs which will give you more dexterity.

We also use the Q-tips to help with beam molds for the BBR. After applying the plastic strips to the mold pieces using the plastic strips and petroleum jelly, you can flip the swab upside down to slide along the side pieces of the assembled mold. This will keep the plastic strips adhered to the molds better. And last but not least, you can clean your ears on the clock!

View this quick video illustrating the above tips.

- Madison Pohl, Asphalt Institute Asphalt Materials Technician

Technician Spotlight

Tami Steindorf, Tesoro Alaska Refinery, Lab Tech 1

Tami has worked in the laboratory at Tesoro for eight years. Since asphalt production and road construction in Alaska is limited to the summer months, her job also includes testing of other refinery products including jet fuel, gasoline and diesel fuel.

"Taking the NBTC course gave me the background to understand why we run the tests that we do, and how to perform them properly per ASTM and AASHTO methods," says Tami.

"Since the class, I have been able to contact Mike Beavin and use him as a resource to clarify procedures and details about test methods. The MS-25 and MS-26 books have served as great reference materials. We have implemented many of the things that I learned in the course, and are always trying to make the best product possible for our customers," she added.

Learn more about this program at

The Asphalt Institute, in cooperation with the North East Transportation Training and Certification Program (NETTCP) and working with the AASHTO Materials Reference Lab (AMRL) and industry leaders, has developed one consistent, national PG binder technician certification. This map indicates the states that have USERS/PRODUCERS (in yellow), PRODUCERS (in green) and USERS (in brown) who have been nationally certified by the Asphalt Institute’s National Binder Technician Certification program.
Ultimately, the Asphalt Institute would like to see both certified users and producers in every state. There are now 42 states with users and/or producers who are nationally certified by the AI NBTC and the NETTCP programs. Click the map…

Certification: What You Should Know About Training Binder Technicians (free)

Understanding the MSCR Test and its use in the PG Asphalt Binder Specifications (free)

(affordable technology, schedule at your convenience, pause-rewind-understand and email your questions)


Now only $50 in the Asphalt Institute online store. The second printing includes an Appendix on Multiple Stress Creep Recovery (MSCR) testing.
Asphalt Binder Series
(5 - 2 hour sessions)
Recorded Webinars
Part 1 Intro to Asphalt Binders
Part 2 Asphalt Binder Testing & Specifications
Part 3  Asphalt Binder Testing & Specifications (cont.)
Part 4 Asphalt Emulsions, Cutbacks & Air Blown Asphalts
Part 5 Asphalt Binder Modification & Testing Variability

(affordable technology, schedule at your convenience, pause-rewind-understand and email your questions)
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