High-RAP Roadways, Long-Term Aging Concerns, and Asphalt Rejuvenation

Using reclaimed asphalt pavement (RAP) has become a cornerstone of modern roadway mix designs as the asphalt paving industry continues pushing for sustainable practices. RAP offers environmental benefits including reduced reliance on virgin binder and aggregate and potential to lower greenhouse gas emissions.  

However, when proposed RAP levels rise above 25%, concerns about long-term pavement performance also rise. Issues like premature cracking, increased stiffness, and durability loss have made many engineers and mix designers hesitant to specify high-RAP mixtures. 

The question is not whether RAP should be used: it is how to use it effectively. This is the gap asphalt rejuvenators like ReLIXER® are designed to address. By selecting the right rejuvenator, producers can mitigate the risks of excessive stiffness and long-term aging while unlocking the full value of RAP, even up to 100%. 

The Promise and Challenge of High-RAP Mixes 

RAP is one of the most recycled materials in the world, with millions of tons reused annually in new pavements. Using RAP helps reduce landfill waste, conserves natural resources like virgin aggregate and asphalt binder, and reduces overall material costs. Many agencies already allow up to 15-20% RAP with minimal concerns. But when specifications push toward 30%, 40%, or even higher, the challenges of premature aging of roadways become harder to ignore. 

One factor is that the asphalt binder in RAP has undergone years, often decades, of environmental exposure. Sunlight, heat, moisture, and oxygen drive the oxidative aging process, leaving the RAP binder stiff and brittle. When this aged binder is blended into a new mix without proper rejuvenation, it can degrade the overall binder properties, leading to: 

• Increased risk of cracking (thermal and fatigue) 

• Reduced flexibility and toughness 

• Concerns about durability and performance under traffic loads 

For many contractors and departments of transportation, the fear of sacrificing long-term pavement performance overshadows the sustainability and cost benefits of using higher RAP levels. That's why rejuvenation technology is critical. 

How Asphalt Rejuvenators Help High-RAP Mixes 

An asphalt rejuvenator is designed to restore the functional properties of the aged binder contained in RAP. A well-formulated rejuvenator can allow higher percentages of RAP to be used while maintaining or improving performance metrics such as cracking resistance, fatigue, and overall durability. 

High-performing asphalt rejuvenators can: 

• Provide rapid penetration into the RAP particles 

• Adjust performance grade and rheology 

• Improve workability to aid compaction 

• Promote long-term durability 

• Support sustainability goals 

Without an asphalt rejuvenator, high-RAP mixes can compromise performance outcomes. However, with the right recycling agent, high-RAP roadways can achieve sustainability and longevity specifications. 

What to Look for in an Ideal Asphalt Rejuvenator 

Choosing the right asphalt rejuvenator can help ensure consistent performance, long-term durability, and ease of implementation. When evaluating a rejuvenator for high-RAP applications, here are the key attributes to consider: 

1. Proven Compatibility with RAP Binders A rejuvenator must demonstrate compatibility with aged binders. Not every product interacts well with every type of RAP source, so proven lab and field performance data are critical. 
2. Restores Performance Balance The goal of a rejuvenator is to do more than simply soften the aged binder. A good asphalt rejuvenator achieves functional balance between cracking resistance and rutting resistance. 
3. Long-Term Aging Resistance An asphalt rejuvenator should initially revitalize the binder while also helping to resist further aging. Products designed with long-term durability in mind provide value well beyond the first few years of service. 
4. Ease of Use in Production From plant integration to dosage rates, a practical rejuvenator must be straightforward to incorporate into existing operations without excessive modification. The health, safety, and environmental (HS&E) concerns of plant operators must also be considered. 
5. Environmental Responsibility Since RAP use is tied closely to sustainability, an ideal rejuvenator should align with that mission. The additive should offer a reduced carbon footprint and minimal additional environmental impact through product use. 

ReLIXER® Asphalt Rejuvenator for High-RAP Roadways  

ReLIXER asphalt rejuvenator was engineered with these performance needs in mind. Formulated to restore balance to aged binders, ReLIXER enables producers to design high-RAP mixes that perform as well as traditional no-RAP or low-RAP mixes. 

Key benefits of ReLIXER include: 

• Higher RAP Utilization: Allows use of over 25% RAP without compromising pavement life 

• Balanced Mix Design: Improves cracking resistance while maintaining rutting resistance 

• Proven Durability: Demonstrates strong performance in lab testing, field trials, and proven roadway performance over time 

• Easy Integration: Simple to dose and incorporate into existing mix production 

• Sustainability Gains: Supports agencies in meeting emissions goals 

ReLIXER and High-RAP Roadway Durability Profile 

A durability study was conducted to evaluate the effects of high-RAP content and different asphalt rejuvenators on cracking resistance, measured using the CT Index at 25 °C. Mixtures with no RAP (5.5% virgin asphalt) demonstrated baseline performance, showing a progressive loss of fracture resistance with increased aging time (4, 8, and 16 hours). At 30% RAP, mixes without rejuvenator or those dosed with petrochemical oil showed significant reductions in CT Index after aging, indicating increased brittleness. In contrast, 30% RAP mixtures treated with 3% ReLIXER maintained higher CT Index values over time, demonstrating improved resistance to long-term aging.  

The same trend was observed at 50% RAP. While petrochemical oil provided limited initial benefits, it failed to sustain fracture toughness after aging, whereas mixes incorporating ReLIXER consistently achieved CT Index levels comparable to or better than the no-RAP control. These results indicate properly dosed ReLIXER effectively restores balance to aged binders, enabling 30-50% RAP mixes to perform comparably with low-RAP or virgin mixes even under extended aging conditions.  

Building Confidence in High-RAP Roadways 

The industry is standing at a crossroads. Sustainability demands that we make greater use of reclaimed materials like RAP. Yet, long-term performance concerns continue to hold back wider adoption of high-RAP designs. The key to bridging this gap lies in science-backed rejuvenation solutions. By choosing an effective rejuvenator, contractors can confidently produce high-RAP mixtures without fear of compromising roadway performance.  

The asphalt paving industry will only continue to favor more sustainable mix designs. High-RAP mixtures are central to that vision, but they must be supported by rejuvenation technologies that address aging concerns. ReLIXER offers a proven pathway to leverage high-RAP designs without sacrificing long-term performance. 

To learn more about asphalt rejuvenation and ReLIXER, contact info@sripath.com.