Clarifying NCAT’s Role and Findings Reported in the Article “Reverse the Effects of Asphalt Aging After Dark”
BY Raquel Moraes, Ph.D.
Providing context and accuracy for findings in “Reverse the Effects of Asphalt Aging After Dark”
An article in the September 2025 edition of AsphaltPro regarding spray-on rejuvenators and nighttime application referenced research conducted at the National Center for Asphalt Technology (NCAT). While NCAT appreciates the industry’s enthusiasm for advancing pavement treatments, several points in the article require clarification to ensure the published information accurately reflects the work performed and the scope of involvement of both NCAT and the Alabama Department of Transportation (ALDOT).
Application Conditions
Spray-on rejuvenators have been successfully applied at the NCAT Test Track both day and night, provided ambient and surface temperatures met the product specifications, typically 10°C (50°F) or higher, and surface conditions were suitable.
Curing time depends on dosage, pavement texture, permeability, and environmental factors, rather than on whether it is daylight or darkness. NCAT research has shown that, under proper conditions, both daytime and nighttime applications can achieve acceptable curing and reopening intervals.
Clarifying the 2018-2021 NCAT Test Track Research
The article referenced the 2018-2021 NCAT Test Track research cycle, during which two, not three, spray-on rejuvenators were evaluated on Section S3. This work was sponsored by the Mississippi Department of Transportation (MDOT). All applications occurred during daylight hours, following standard temperature and pavement condition criteria. The purpose of the study was to evaluate the performance of spray-on rejuvenators over time, not to test nighttime applications or new application systems. The claim that friction loss was due to the distributor application method is inaccurate; friction recovery after spray-on rejuvenator application depends on multiple factors, including formulation, dosage, and characteristics of the surface layer.
Figure 1. iEmulsion’s US-280 evaluation. Photo courtesy of NCAT
Differentiating Between NCAT Research and iEmulsions’ Evaluations
It is essential to distinguish between two separate efforts:
- NCAT Test Track Section S3 (2018-2021): Delta Mist was applied to a dense-graded asphalt surface to study binder rejuvenation over an extended period.
- S. 280 Small-Scale Evaluation (2023): Conducted at iEmulsions’ request, this was a limited laboratory-linked test assessing the short-term binder response of Delta Mist HR combined with an SBR-based polymer (UP-40) on an open-graded friction course (OGFC) surface.
These studies differed in materials, surface types, and objectives and should not be presented as equivalent or sequential experiments.
Scope of the U.S. 280 Evaluation
The April 2023 test near Auburn, Alabama, was designed to extract and analyze field cores from small, controlled test spots (approximately 2 feet × 5 feet) without affecting normal traffic (See Figure 1). All applications were conducted during the day using manual spraying, not the two-bar Smart Spray Technology (SST) system described in the article.
NCAT’s role was limited to applying materials and conducting a few rheological tests [complex shear modulus (|G*|), absolute viscosity (η*), and phase angle (δ)] at 60°C and 76°C on binders recovered immediately after treatment application, per the sponsor’s request. Test results confirmed short-term binder softening and increased phase angle, indicating rejuvenator-binder interaction, but did not assess long-term performance.
NCAT emphasizes that short-term softening alone does not predict durability or overall field performance; ongoing monitoring is required to make such conclusions. Importantly, ALDOT was not involved in this small-scale evaluation.
Friction Testing and Data Interpretation
Friction was measured on the treated OGFC spots using a Dynamic Friction Tester (DFT), shown in Figure 1. Results indicated that friction values returned to neutral levels within two hours under the specific materials, conditions, and weather conditions during testing. These findings are encouraging but limited. They should not be generalized to broader pavement types or used to substantiate unrestricted nighttime application performance claims.
Later Demonstrations and Clarification of NCAT’s Role
Subsequent field demonstrations of Delta Mist HR and the Smart Spray Technology system—conducted in Virginia, Arizona, and California—were organized by iEmulsions and partner organizations, without NCAT’s participation. NCAT’s involvement was limited to the April 2023 U.S. 280 binder evaluation, which was conducted entirely under daytime conditions and did not utilize the two-bar SST application.
Summary and Forward-Looking Perspective
NCAT supports efforts that advance asphalt rejuvenation technology and appreciates collaboration across research, industry, and agency partners. However, ensuring that publicly shared information accurately represents the scope, methods, and outcomes of each study is critical to maintaining scientific integrity and public trust.
Spray-on rejuvenators show strong potential to extend pavement life and increase maintenance flexibility. As research continues, NCAT remains committed to transparent data sharing and to helping the industry make decisions grounded in verified evidence.
Editor’s Note: AsphaltPro regrets any misinformation making it to print and has removed the article in question from our website. We want to thank the NCAT staff for providing clarification on a document that was submitted for publication in the September PreservationPro. We are thankful for the collaborative spirit bringing accuracy and transparency to this topic.