The global asphalt market is projected to reach 225.9 million tons by 2030. This is largely attributed to rapid growth in global infrastructure as demand for both new and refurbished roads takes the spotlight. Yet there are concerns that increasing road projects will impede environmental conservation efforts aimed at net zero carbon emissions.  

 

One way the industry is looking to reduce its carbon footprint is by using reclaimed asphalt pavement, or RAP. Produced from leftover aggregate and binder removed from existing roadways and construction projects, RAP holds great potential for helping with sustainability efforts while also cutting costs.  

 

With over 750 million tons of RAP generated each year, there is ample opportunity to make better use of this byproduct. However, only 20% is recycled globally with the remainder shipped to landfills and forgotten.  

 

A pivotal challenge to using high amounts of RAP is that it requires an effective asphalt rejuvenator to restore the properties of the aged asphalt contained in the material. Without an asphalt rejuvenator, mixes are limited to using less than 10-15% total of RAP in their mixes.  

 

Here, we’ll explore asphalt rejuvenation including what it is and why it is becoming increasingly important across the global paving industry. 

An asphalt rejuvenator is an additive that can restore the functional properties of aged asphalt binder, also known as bitumen.  

 

Consider that reclaimed asphalt pavement typically comes from long-used roadways subjected to high traffic and extremes in weather conditions. Over time, the binder properties deteriorate, causing the material and the roadway to lose some of its original durability, adhesion, and flexibility. This surface material is then mechanically removed from the road and becomes RAP that is stored in piles, further exposed to the elements, until it is used. 

 

To use RAP in a mix, it must be rejuvenated or have its properties restored so it can effectively bind materials together when creating a new roadway with desired properties and durability. While the aggregate does not change with age, the binder can oxidize and change chemically and physically over time.  

 

Rather than introducing large amounts of virgin binder to the mix, mix plants can incorporate lower doses of an effective asphalt rejuvenator to restore the functional properties of the material. Asphalt rejuvenators restore functional properties, enabling the binder to do its original job on the roadway. 

High-RAP mixes are those that include more than 25% recycled asphalt pavement in their mix. While the benefits of this are many, including sustainability and cost savings, there are physical limitations to adding large amounts of RAP to a mix.  

 

For a roadway mix to endure harsh conditions, the mix needs to be able to perform according to measures of cracking, aging, compaction, and durability. Old asphalt binders simply do not have enough physical characteristics remaining to perform to standard. Adding an asphalt rejuvenator can restore functional performance of aged asphalt. Effective asphalt rejuvenators have been shown to maintain or exceed performance specifications with up to 100% RAP in the mix.  

While an effective asphalt rejuvenator can aid with softening requirements, not all bitumen, or asphalt, softeners are rejuvenators. The primary goal of a bitumen softener is to adjust the penetration or PG low grade of the binder. This softening alone does not have rejuvenating effects such as rebalancing aged binder characteristics or restoring similar behavior and performance as virgin binder.  

Rejuvenators can come in several varieties and with varying degrees of effectiveness. Petroleum-based asphalt rejuvenators can include oils such as paraffins, aromatics, and naphthenics. Used cooking oil, soft grades, and REOB (such as used motor oil) have also been used as rejuvenators to varying degrees of effectiveness while raising questions regarding performance and safety.  

 

While most of these options are byproducts of other processes, bio-based oils are another category of asphalt rejuvenators that are intentionally crafted as virgin products to address specific functional properties in a mix.  

In particular, bio-oil based asphalt rejuvenators can enhance functional properties without introducing harmful chemicals or oils into the mix. By restoring the original binder in the RAP, less virgin binder is also needed, alleviating the need for new materials sourced from crude oils that draw from natural resources. 

 

In addition, bio-based products that leverage crops can also lower the overall carbon footprint of a roadway by capturing carbon produced by the plants. This process, known as biologic carbon sequestration, allows carbon from bio-based oils to be stored in the asphalt pavement moving forward. 

 

Improving roadway performance and durability for the long term through use of effective rejuvenators or recycling agents in high-RAP mixes can also prove effective in Life Cycle Analysis (LCA) analyses, reducing the requirements for less ecofriendly and more frequent repairs and replacements in the future. 

Asphalt rejuvenation and ReLIXER® 

ReLIXER, an asphalt rejuvenator or recycling agent, is specifically designed to deliver excellent low temperature properties and aging performance. An elixir of bio-based oils, ReLIXER has not only demonstrated performance for mixes with any level of RAP content, but it also helps lower greenhouse gas emissions and overall energy consumption. An effective asphalt rejuvenator, ReLIXER is compatible with binders from global sources and can also help lower mix costs by 5-15%.