Thesis
Laboratory and field evaluation of high-RAP mixes with warm and rejuvenating additives
University of Iowa
Master of Science (MS), University of Iowa
Spring 2026
DOI: 10.25820/etd.008376
Abstract
Asphalt pavement production accounts for significant environmental impact and monetary cost due to the limestone aggregates and oil-based binder used in its mix design. Incorporating reclaimed asphalt pavement (RAP) into new asphalt reduces these issues, yet high- RAP mixes remain underutilized because they generally exhibit lower cracking resistance than virgin asphalt. To determine if additives can improve the cracking performance of high-RAP mixes to acceptable levels while maintaining adequate rutting performance, three commercially available additives (Zero-M, Anova, and Evoflex CA) were evaluated in mixes containing 20%, 30%, 40% and 50% RAP. The three additives differ in their properties. Zero-M is a polymer cool-mix additive, Anova is a bio-based rejuvenator, and Evoflex CA is an engineered asphalt additive and rejuvenator. Cracking resistance was assessed using the IDEAL-CT test with a target CT Index of 30 or more, while rutting susceptibility was measured via the Hamburg wheel tracking test (HWTT).
The results demonstrated that a control mixture with no additive failed to meet the minimum CT Index at 30% and higher RAP content. However, certain additives were shown to enable high-RAP mixtures to surpass the minimum cracking performance threshold. Evoflex CA, using a 7.5% RAP-binder replacement dosage, attained an average CT Index of 30.2 while maintaining an average maximum rut-depth of just 4.66 mm at 30% RAP. Zero-M, utilizing a different 5% total-binder replacement dosage, had acceptable performance up to 40% RAP. This mix achieved an average CT Index of 40.0 and an average maximum rut depth of 8.1 mm. The Anova rejuvenator was the only product that failed to meet the minimum cracking performance in laboratory testing across all RAP contents. However, it exhibited better performance in plant- mixed field test sections, achieving the highest average CT Index of 54.0. In this study, Anova performed substantially better when plant-mixed than when laboratory-mixed. Field evaluations highlighted the importance of construction practices and mix design for real-world durability.
In the Jones County field section, several of the 35% RAP sections with higher in-place air voids also exhibited greater observed cracking, indicating that compaction likely played a major role in early cracking performance. However, because the section was a thin overlay on a severely aged pavement, these early field observations were likely heavily influenced by reflective cracking. Furthermore, IDEAL-CT testing of the extracted field cores yielded highly inflated CT Index values compared to laboratory-compacted specimens due to field compaction mechanics, though the Zero-M modified mixture maintained the highest relative flexibility. Additionally, the follow-up survey of the Cerro Gordo County test section showed that the 34%RAP section using a softer virgin binder exhibited better observed long-term cracking performance than the rejuvenated sections evaluated here. These findings indicate that, with an appropriate additive and dosage, high-RAP mixtures can achieve acceptable laboratory cracking and rutting performance up to 40% RAP in this study and may reduce virgin material use, cost, and environmental burden relative to lower-RAP mixtures.
Details
- Title: Subtitle
- Laboratory and field evaluation of high-RAP mixes with warm and rejuvenating additives
- Creators
- Giuseppe Gianforte
- Contributors
- Hosin Lee (Advisor)Paul Hanley (Committee Member)Asghar Bhatti (Committee Member)
- Resource Type
- Thesis
- Degree Awarded
- Master of Science (MS), University of Iowa
- Degree in
- Civil and Environmental Engineering
- Date degree season
- Spring 2026
- DOI
- 10.25820/etd.008376
- Publisher
- University of Iowa
- Number of pages
- xiv, 100 pages
- Copyright
- Copyright 2026 Giuseppe Gianforte
- Language
- English
- Date submitted
- 04/23/2026
- Description illustrations
- illustrations, tables, graphs
- Description bibliographic
- Includes bibliographical references (pages 71-72).
- Public Abstract (ETD)
Asphalt pavement uses oil-based binders, so producing new pavement has environmental and cost impacts. Replacing some new materials with reclaimed asphalt pavement (RAP) reduces those impacts, but mixes with high RAP contents are generally more prone to cracking. This study evaluated whether three commercial additives, Zero-M, Anova, and Evoflex CA, could improve the cracking resistance of mixes containing 20%, 30%, 40%, and 50% RAP without reducing rutting resistance.
Laboratory testing showed that mixes with no additive failed the minimum cracking threshold at RAP contents of 30% or higher. Evoflex CA allowed the 30% RAP mix to meet that threshold. A modified Zero-M dosage provided acceptable cracking and rutting performance up to 40% RAP. Anova did not meet the laboratory cracking threshold in laboratory-mixed specimens, but it performed much better in the plant-mixed material used for the Jones County field section.
Field evaluation in Cerro Gordo and Jones Counties showed that construction and roadway conditions affected performance. In Jones County, higher in-place air voids in several 35% RAP sections aligned with more cracking, although reflective cracking, roadway geometry, and short section length also influenced the results. Testing of extracted field cores also produced inflated cracking scores compared with laboratory-compacted specimens. In Cerro Gordo County, the 34% RAP section with a softer virgin binder showed less crack growth over time than the rejuvenated sections.
Overall, the results show that, for the mixtures evaluated here, selecting the additive and dosage can support acceptable performance up to 40% RAP while reducing virgin material use.
- Academic Unit
- Civil and Environmental Engineering
- Record Identifier
- 9985176871202771
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