Demand for sustainable roadway solutions continues to grow as transportation agencies work to address both performance specifications and carbon emission standards. One technology rising in global popularity is the use of reclaimed asphalt pavement (RAP) along with an asphalt rejuvenator. Asphalt rejuvenation helps to restore the functional properties of the aged binder in RAP, enabling higher percentages of RAP to be used. In turn, contractors can produce more environmentally responsible and economically viable roadway surfaces.  

 

Meeting Sustainability Goals in Roadway Construction 

Asphalt is a mainstay in traditional road construction, relying heavily on virgin binder and fresh aggregates. However, these materials can be resource-intensive to produce and transport. The energy required to heat and mix hot mix asphalt (HMA), combined with the emissions generated during production and paving, contributes to each asphalt roadway project’s environmental footprint. Asphalt paving is also used across over 90% of roadways in the U.S. alone, and demand for new and rehabilitated infrastructure worldwide is leading to fast-rising use.  

 

To address these issues, RAP usage is becoming more widespread. Once considered a waste material left to take up space in landfills, RAP is now recognized as containing valuable aggregates and binder that, when properly treated, can be reused in new asphalt paving projects. However, incorporating high RAP content into mixes without compromising performance remains a technical challenge. 

 

What is Asphalt Rejuvenation? 

One of the reasons existing roadways fail, and are milled into RAP for resurfacing projects, is the aging process that bitumen undergoes over time. This essential binder oxidizes through prolonged exposure and use, becoming stiff and brittle. The aging process can lead to roadway cracking, raveling, and other roadway failures.  

 

Asphalt rejuvenators are helping solve the issue of RAP performance in asphalt mixes for new roadway surfaces. These asphalt recycling agents enable mix designers to incorporate high amounts of RAP without sacrificing long-term performance. Effective asphalt rejuvenators are specially engineered additives that help restore the functional properties of the aged binder, improving its ductility, workability, and overall performance in newly developed mixes.  

 

Achieving Sustainability in Asphalt Paving with Asphalt Rejuvenation 

The process of asphalt rejuvenation can enable engineers to reduce virgin binder and fresh aggregate in a mix design, potentially reducing both costs and carbon emissions. Using higher percentages of RAP in asphalt mixes is one of the most effective ways to reduce environmental impact and lower costs associated with raw materials. But without an asphalt rejuvenator, high-RAP mixes may fail prematurely due to the stiffness of the aged binder. 

 

Rejuvenators enable producers to significantly increase RAP content. High-RAP mix typically contain 25% or higher percentage of RAP. With an ideal asphalt rejuvenator, RAP levels in excess of 50% can be used,  and in some cased, as high as 100% RAP has been used. This not only cuts the amount of virgin binder required but also reduces landfill waste and the energy associated with producing and transporting raw materials. 

 

In addition to performance gains, asphalt rejuvenators help contractors meet sustainability goals such as EPD targets and reduced life-cycle emissions requirements. However, not all asphalt recycling agents are sustainable products themselves. Many are developed with a petroleum base including paraffinic, aromatic, or naphthenic oils. Others are formulated using recycled materials such as used cooking oils and re-refined engine oil bottoms (REOBs) that pose their own challenges (both in performance and ecological impact) in asphalt paving use. This makes it important for producers to consider the environmental effect of a recycling agent in order to meet broader sustainability goals.  

 

Asphalt Rejuvenation, Sustainability, and ReLIXER® 

ReLIXER® is formulated from a blend of bi0-based oils sourced from crops that do not impact food sources. Publicly available Environmental Product Declaration (EPD) documentation demonstrates a negative value for global warming potential (GWP) for ReLIXER, ensuring that use of the asphalt rejuvenator improves overall sustainability goals for producers.  

 

ReLIXER has demonstrated excellent low temperature properties and aging performance in mixes, enabling long-lasting, durable roadways and minimizing the need for costly and unsustainable repairs or resurfacing. ReLIXER has been shown to work in roadway surfacing applications using varying amounts of RAP sourced from all over the world. In global applications, ReLIXER has also enabled high-RAP uses in regular binder mixes, PMB binder mixes, air-oxidized binder mixes, and SMA mixes. The result can be a more cost effective, sustainable roadway that meets specifications.  

 

Mix Design Considerations for RAP and Asphalt Rejuvenation 

Asphalt rejuvenation is just one aspect of mix design for achieving sustainable roadways. To successfully incorporate high levels of RAP, mix designers must also address aggregate gradation, moisture content, and blending efficiency. The rejuvenator must also be carefully dosed based on RAP characteristics.  

 

This approach, called Balanced Mix Design (BMD), relies on achieving performance specifications based on performance testing rather than traditional volumetric measures. This can help mix designers achieve asphalt pavements that incorporate high amounts of RAP while also combatting performance issues such as rutting, aging, fatigue, and cracking. By implementing BMD, the asphalt paving industry can create durable roadways made from recycled materials proven to last.  

 

For more information about asphalt rejuvenation, RAP, BMD, and ReLIXER, contact info@sripath.com. Â