Asphalt producers and contractors looking to strengthen their competitive position in today’s infrastructure market are turning to reclaimed asphalt pavement (RAP) as a strategic resource. The numbers tell a compelling story: the National Asphalt Pavement Association (NAPA) estimates that RAP used in asphalt mixtures during the 2018 construction season reached 82.2 million tons, a 7.9% increase over the prior year. Since NAPA and the Federal Highway Administration (FHWA) began surveying recycled material use in 2009, overall RAP consumption in mixtures has risen by 46.8%. These figures reflect a growing recognition among state agencies, contractors, and material suppliers that higher RAP content delivers measurable economic and environmental benefits. Understanding how to increase RAP production requires careful attention to material processing, additive chemistry, mix design, and quality control. Contractors may also benefit from considering how material selection principles apply across different construction contexts, much like the guidance found in Everything You Need to Know About What You emphasizes the importance of understanding foundational requirements before proceeding with specialized work.
The Case for Higher RAP Content
Reclaimed asphalt pavement has become one of the most valuable resources available to the asphalt industry. When processed correctly and incorporated at appropriate percentages, RAP reduces the need for virgin aggregates and liquid asphalt binder, lowering material costs while conserving natural resources. The trend toward higher RAP content is driven by economic pressures, environmental regulations, and years of field performance validation.
Growth in RAP Adoption
The number of states where asphalt producers report using RAP at 20% or higher reached 30 in the 2018 NAPA survey, up from 24 in 2017 and just 10 in 2009. This threefold increase in under a decade demonstrates that confidence in high-RAP mixes has grown substantially as agencies develop performance-based specifications and gain field experience with recycled materials. The global market for asphalt additives enabling higher RAP content is projected to grow by $2.7 billion between 2020 and 2029, reflecting strong demand from producers pushing beyond conventional RAP limits.
Key Drivers Behind the Shift
- Cost savings on virgin material: Replacing virgin aggregates and binder with RAP directly reduces raw material costs. At high production volumes, even a 5-10% increase in RAP content translates into significant annual savings.
- Reduced disposal fees: Using reclaimed material diverts pavement from landfills, eliminating tipping fees and environmental liability.
- Lower carbon footprint: RAP reduces energy for mining, crushing, and transporting virgin aggregates, plus emissions from new binder production.
- Performance-based specifications: More agencies are moving from recipe-style designs toward performance specifications that set engineering targets for rutting, cracking, and moisture resistance.
- Agency mandates: Many state DOTs now include minimum recycled content requirements in contracts, making RAP capability a prerequisite for bidding on public projects.
How Additives and Rejuvenators Enable High-RAP Performance
The primary technical challenge with high-RAP mixes is the aged binder contained in the reclaimed material. Over years of service, the binder oxidizes and becomes stiff and brittle. At high RAP percentages without corrective measures, the pavement may be prone to cracking and reduced fatigue life. Rejuvenators and other additives address this problem directly.
How Rejuvenators Work
Rejuvenators are chemical additives that restore the rheological properties of aged asphalt binder. They replenish the lighter fractions lost during oxidation, softening the aged binder and improving its resistance to thermal and fatigue cracking. As Hassan Tabatabaee, global technical manager of Asphalt Solutions at Cargill, explains, additives play a significant role in enriching the types of pavements the industry can produce. The right additive, combined with proper mix formulation, allows contractors and agencies to achieve performance that rivals or exceeds virgin mixes. Dosage varies based on RAP content, binder age, and performance targets. Tabatabaee compares the process to baking: there is no standard amount that works for every recipe, and specific dosage must be tailored per mix and application.
Additive Options for High-RAP Mixes
| Additive Type | Primary Function | Typical RAP Range | Key Consideration |
|---|---|---|---|
| Bio-based rejuvenators | Restore maltene fraction; improve low-temperature cracking resistance | 25-50% | Renewable source; dosage sensitive to RAP binder age |
| Petroleum-based rejuvenators | Softened aged binder; improve fatigue life | 20-45% | Consistent chemistry; proven field performance |
| Warm-mix additives | Lower production temperature; reduce binder viscosity | 15-40% | Enables higher RAP by reducing plant heat needs |
| Polymer modifiers | Improve rutting resistance and stiffness | 15-35% | Best combined with rejuvenators for balance |
| Anti-strip agents | Improve moisture resistance and adhesion | 10-30% | Critical with moisture-sensitive aggregates |
Real-World Success Stories
Two state agency case studies demonstrate how strategic use of RAP with the right additives delivers substantial cost savings and performance improvements.
Delaware: Small State, Big Results
The Delaware Department of Transportation (DelDOT) maintains 90% of roads in a state spanning roughly 100 miles north to south. Its small footprint enables quick, centralized decision-making that accelerated RAP adoption. Today DelDOT uses an average of 25% RAP and 4% recycled asphalt shingles (RAS) in mixtures. The agency began incorporating RAP during the 2009 recession as a cost-saving measure at about 18% RAP. After Hurricane Sandy in 2012, a large volume of shingles hit the market. Initial performance testing showed concerning brittleness with low cycles in the Texas Overlay Test. Following collaboration with Cargill on ANOVA rejuvenator samples, test results showed dramatically decreased cracking. After pilot projects on roads around Kent County and evaluation including long-term aging specimens, the supplier began using rejuvenator in all state top-layer material produced at its hot mix plants.
Illinois Tollway: Savings at Scale
The Illinois Tollway implemented new performance-based specifications that set actual performance targets rather than recipe approaches. This led to higher recycled content and early performance improvements. Over 10 years, the agency saved roughly $200 million through recycled material reuse, reduced virgin purchases, and lower disposal fees, according to Paul Kovacs, the authority’s chief engineer. The Jane Addams Memorial Tollway reconstruction used recycled asphalt in approximately 33% of new mainline asphalt and about 50% of shoulder material. The project served as a testing ground for RAP and additives throughout other Tollway projects.
Lessons Learned
- Start with pilot projects. Both agencies used controlled field trials before widespread use, building confidence and generating data for specification changes.
- Test thoroughly before scaling. DelDOT’s long-term aging analysis and Texas Overlay testing confirmed that the rejuvenator solved the brittleness problem.
- Partner with additive suppliers. Direct collaboration with chemistry experts optimizes dosage and avoids costly field trial-and-error.
- Adopt performance-based specifications. Moving from recipes to performance targets allows innovation while ensuring durability.
- Document and share results. Case studies accelerate industry-wide progress toward higher RAP utilization.
Best Practices for Scaling RAP Production
Producers looking to increase RAP content should take a systematic approach to material management, processing, quality control, and collaboration.
RAP Inventory and Processing
- Stockpile RAP by source and binder content for consistent blending ratios.
- Crush and screen RAP to uniform gradation matching the target mix design.
- Monitor moisture content in stockpiles, as excess moisture affects production rates and mix temperatures.
- Remove contaminants through proper processing and inspection.
- Conduct regular binder extraction and recovery testing to track RAP binder properties over time.
Mix Design and Quality Control
- Determine the RAP binder availability factor representing the fraction of aged binder that blends with virgin binder during production.
- Select rejuvenator type and dosage based on target binder performance grade, not just RAP percentage.
- Verify moisture resistance through AASHTO T283 testing, especially with marginal RAP aggregates.
- Evaluate cracking resistance using the Texas Overlay or Semi-Circular Bend test for surface-course mixes.
- Conduct plant trial runs before full production to confirm mix properties at production temperatures.
Collaboration with Agencies and Partners
Proactive collaboration with state agencies, the FHWA, and suppliers is one of the most effective ways to advance higher RAP content. As Tabatabaee notes, an important portion of supplier efforts focuses on partnering with each customer for the right dosage and formulation. Contractors who engage gain access to technical expertise and laboratory resources difficult to develop independently. Opportunities include participating in agency research, contributing to pooled-fund studies, hosting field demonstrations, and sharing pilot project data. For a broader view of how project delivery methods affect construction outcomes, see Everything You Need to Know About Project Delivery, which outlines how procurement approaches influence material selection and quality.
Plant Modifications for High-RAP Production
RAP content above 25% often requires plant modifications for adequate heat transfer and mixing. Moisture in RAP and the need to heat reclaimed material without damaging aged binder present specific challenges.
- Use a separate RAP feed system with variable-speed control for precise metering.
- Install a parallel-flow drum or separate RAP dryer to preheat material before mixing.
- Monitor baghouse temperatures to prevent combustion of RAP fines in the dust collection system.
- Consider warm-mix technologies to lower production temperatures and allow higher RAP percentages.
- Calibrate liquid additive systems for precise rejuvenator dosing with automated controls.
For operations exploring plant upgrades, understanding the full range of production equipment is essential. The guide on Asphalt Plants and Pavement Construction Equipment a Complete provides detailed information on plant configurations for hot mix asphalt production.
Material selection decisions are only part of the broader construction quality equation. Attention to how materials perform within the full assembly is equally important, as highlighted in the discussion of Rigid Foam Sheathing Placement Should You Insulate Inside, which demonstrates how placement strategy affects overall system performance. Contractors who systematically collect and analyze performance data position themselves as trusted partners for agencies looking to expand recycled material use. The long-term trend is clear: RAP content will continue rising as agency confidence grows, additive technologies improve, and economic and environmental pressures favoring recycling intensify.