Others do not ban it by specification, but have agreements with asphalt suppliers to avoid the use of REOB.
To execute the plan, TFHRC provided the initial test method and 45 blends of various REOB modified asphalt binders with REOB concentrations of 2, 5, 8, 10, and 20 percent.
The unanswered question that remains is whether REOB negatively influences pavement life.
The pavement without REOB on one segment of Highway 655 showed no distress after 9 years of service.
Similarly, a section of test pavement in Minnesota (MN1-4) found to contain REOB also cracked prematurely.
In fact, it was difficult for researchers to assess whether REOB was present.
Some evidence suggests that the presence of REOB may be detected using the bending beam rheometer.
Two independent study teams, one from AASHTO and the other from the Asphalt Institute, concluded that more research is needed on the use of REOB in asphalt.
Then 19 percent REOB would soften it and bring it back within specification.
X-ray fluorescence spectroscopy can find REOB and phosphoric acid, and the handheld spectroscopy works for spot checks.
The TFHRC team will soon submit to AASHTO the draft test methods that transportation agencies can use to test for the presence of REOB in asphalt mixes.