Agencies buy asphalt rejuvenators on a promise. There is no agreed industry definition of what rejuvenation is, and no accepted test that proves a treatment changed the binder at the molecular level. A chemistry and civil engineering team at Missouri University of Science and Technology is trying to close that gap. It has no published results yet.
The work, described in a Sept. 28 release from the Missouri S&T news office, runs asphalt binder through nuclear magnetic resonance relaxometry. Samples go into test tubes, the tubes go into the NMR, and researchers measure how fast the excited material returns to its normal state. Klaus Woelk, a professor of chemistry at the Rolla campus, leads the team. His framing: “It’s like an MRI for early cancer detection, but for asphalt failure.”
Binder is the tar byproduct of crude oil refining, mixed with crushed rock and limestone to make pavement. It ages under ultraviolet light, oxygen exposure and the freeze-thaw cycle. Aged binder turns brittle, loses elasticity and cracks. Rejuvenator oils are sold to reverse that, and state DOTs have been buying them for years on the strength of supplier data.
What NMR relaxometry can see inside an asphalt core sample
Rebecca Herndon, a research collaborator in Woelk’s lab who holds a bachelor’s degree and a Ph.D. in civil engineering from Missouri S&T, described the market she’s testing into. “Right now, it is the Wild West of research and development, because there is not a firm definition of rejuvenation for asphalt,” she said. “Measuring the microstructure in asphalt core samples with NMR is useful because we can detect the difference between new, aged, and rejuvenated sections.”
That last clause is the claim worth tracking. If the method reliably separates new, aged and rejuvenated material inside one core, an owner gets something it doesn’t have today: a before-and-after acceptance test on a preservation treatment. The current method is to spread the product across 40 lane-miles and find out in four years by counting cracks.
The team is pulling cores from a spread of climates because the chemistry doesn’t travel. “The needs for roads in Minnesota will be very different from Louisiana roads, because the local climate has a huge impact,” said Catherine Skaggs, a junior in chemistry on the team. Rosalee Brown, a senior in chemical engineering, is the other undergraduate researcher. Corrective Asphalt Materials and the Missouri Department of Transportation supply the road cores, and the team says it is sharing findings with MoDOT staff.
Why an asphalt rejuvenation standard would rewrite preservation specs
Woelk’s stated endgame is a standard. Certification against one “would be a huge selling point for companies that mass produce these rejuvenation oils and contract with various transportation departments throughout the country,” he said. That is the supplier’s read on the upside, and it’s a fair one. The owner’s read is the mirror image: a standard is also the instrument that lets an agency reject a load, fail a section, or hold retainage.
Be precise about what this is and isn’t. No paper, no journal, no DOI, no sample count, no disclosed funding source. Nobody has published a pavement-life extension figure out of this lab, so any percentage attached to the method did not come from the researchers. Corrective Asphalt Materials is named as a sample-supply collaborator, not as a validator of the technique, and the release doesn’t say whether MoDOT is funding the work or only handing over cores.
Research money keeps finding the unglamorous verification problems: why crews won’t switch helmets, how to write embodied carbon into ACI and AISC code. Rejuvenation belongs on that list. Until a test exists, the word on the drum is a marketing term.