What two independent studies — one in the laboratory, one on a full-scale test track under real traffic — tell us about ground tire rubber and aramid fiber in asphalt.
If you build or specify asphalt pavement, you’ve probably fielded some version of this question lately: How does aramid fiber compare to ground tire rubber?
It’s a fair question, and it deserves an honest answer — so let’s start with the honest part. There is no single, dedicated head-to-head study that drops ACE XP™ aramid fiber and ground tire rubber (GTR) into the same mix and races them against each other. Anyone who tells you otherwise is overselling.
What the industry does have is arguably more useful: two independent studies, run by different organizations using different methods — one in the lab, one on a full-scale test track under real traffic. Neither was designed to sell a product. And they point to the same conclusion.
Rubber-modified asphalt can perform — but only when conditions are right. Aramid fiber reinforcement holds up even when they aren’t.
Here’s what the data actually says.
In 2020, the City of Mesa commissioned an independent, PE-stamped laboratory evaluation of ground-tire-rubber asphalt mixtures — cracking resistance and rutting, across rubber-only and polymer-modified-rubber designs, at full and reduced binder content, with and without recycled material.
At its best, rubber-modified asphalt performed well. But the study’s real lesson was how quickly that performance came apart when real-world variables moved off-target:
The takeaway isn’t that rubber is bad. It’s that rubber-modified asphalt is conditional: it depends on getting binder grade, binder content, RAP, and compaction right all at once. Miss one, and cracking resistance falls — sometimes below spec. And real jobsites are rarely that perfect.
(One point of intellectual honesty: the Mesa study tested rubber, not aramid fiber. ACE XP’s results appear alongside it from separate independent programs on different test scales, so we present them as context — not as a head-to-head result.)
The second study is the one engineers tend to find most compelling, because it happened on a real road under real traffic.
The National Center for Asphalt Technology (NCAT) at Auburn University runs an Additive Group experiment on its full-scale Test Track. In Phase II, several additives — aramid fiber, ground tire rubber (both wet and dry process), and others — were each placed in the same base mix and tested against the same premium SBS polymer-modified control, as a “drop-in” with no change to the mix design. The sections were trafficked to roughly 10 million ESALs between 2021 and 2024.
This isn’t a dedicated aramid-vs-rubber test either; it’s a multi-additive program against one common SBS baseline. But because every additive shared the same control, measured on the same scales, it’s the closest thing the industry has to an apples-to-apples comparison. And in the field, the result was clear:
What makes that even more notable: the aramid section was built at a lower in-place density than the control — a compaction disadvantage that typically hurts cracking resistance. It performed in the field anyway.
We’ll be straight about the nuances, because reinforcement claims should survive engineering review. On the laboratory cracking index, aramid landed mid-pack — dry rubber actually scored slightly higher — and the dry-rubber field section sat on a weaker foundation, which drives cracking independent of the additive. So we don’t claim a laboratory cracking win over rubber. What we claim is what the field showed: on a common baseline, under real traffic, aramid held the line on cracking where rubber did not, and led the group in rutting resistance.
The reason these two studies line up comes down to what aramid fiber actually does.
Traditional approaches — rubber and polymer — modify the binder. They change the chemistry of the asphalt cement, which is effective when everything is dialed in, but sensitive to binder content, RAP, temperature, and compaction.
ACE XP™ aramid fiber doesn’t modify the binder. It reinforces the mix itself — high-tensile fibers distributed throughout the asphalt, dosed at the plant, with no change to your binder, your job-mix formula, or how you pave. Think rebar for asphalt, not a chemistry tweak. That’s why it doesn’t hinge on getting every variable perfect: it strengthens every batch the same way.
Aramid fiber’s own independent record reinforces the point — 88% less cracking over seven years on an in-service road, and +110% cracking resistance and +350% fatigue life versus a conventional mix in the lab. And it leans into where the industry is heading: where rubber systems are steered away from high recycled content, ACE XP — and REARM™, our aramid-plus-rejuvenator system — is engineered to unlock up to 50% RAP without the cracking penalty.
Put the two studies side by side and a consistent picture emerges. The lab shows why rubber-modified asphalt is conditional. The field shows that aramid reinforcement holds up where rubber doesn’t — on a common baseline, under real traffic, even built below the control’s density.
That’s the case for ACE XP™: reinforcement you can count on in the real world, not just under ideal conditions.
Rubber is conditional. Aramid fiber is consistent.
Download the full reports and executive summaries here.
Want the full picture? Surface Tech can provide both independent technical evaluations — the City of Mesa laboratory study and the NCAT Test Track field experiment — along with ACE XP's own laboratory and field results. Reach out to your Surface Tech representative or visit surface-tech.com.
Sources: NCAT Additive Group Experiment, Phase II (NCAT Test Track, presented at SEAUPG 2024); City of Mesa / EVAC mix-design performance study (PE-stamped, 2020); independent ACE XP laboratory testing (ASTM D8395-23) and field results. Comparisons are drawn across independent programs and a common-baseline field experiment; they are not a single dedicated head-to-head test.