Bitumen softeners are an important tool in the asphalt industry for maintaining and improving roadway performance. The key advantage of adding softeners to bitumen is their ability to improve low-temperature performance. This results in enhancing penetration, reducing stiffness, and lowering the binder's PG grade to minimize cracking. By restoring workability, bitumen softeners can help maintain the binder's balance between flexibility and strength, ensuring reliable pavement performance. 

 

Because bitumen from different sources will have different properties, maintaining a consistent viscosity, which helps workability, can also be a challenge for producers. Adding a bitumen softener to an asphalt mix can help improve flowability by reducing friction. The result can be a binder that more easily and thoroughly spreads over the aggregate in the mix.  

 

Improving the physical properties of the bitumen can help the binder maintain optimal performance under traffic and environmental stresses after laydown of a roadway. In this FAQ, we'll address some of the most common questions about bitumen softeners including their function, chemistry, environmental impact, and role in sustainable pavement design. 

 

All About Bitumen Softeners 

What is a bitumen softener for asphalt? 

A bitumen softener is an additive used to reduce the stiffness or hardness of bitumen. It restores flexibility and is used to adjust the grade (Penetration, PG Low Grade, Viscosity) of hard virgin bitumen so the binder can better perform in a mix. 

 

How is a bitumen softener different from a bitumen modifier or polymer? 

A polymer or modifier is often designed to enhance strength, durability, or rutting resistance. The primary function of a bitumen softener is to restore or adjust the binder's softness.  

 

Are bitumen softeners used in recycled asphalt pavement (RAP) mixes? 

As asphalt ages, the binder becomes oxidized and brittle, reducing performance. Bitumen softeners can help by reducing the viscosity of the aged binder. However, an ideal asphalt rejuvenator will be more effective for RAP applications since it will also restore the functional properties of the aged bitumen and rebalance the aged binder in the mix and provide long-term durability. 

 

What are the typical types or chemistries of bitumen softeners? 

Common types of bitumen softeners include petrochemical oils, aromatic oils, naphthenic oils, paraffinic oils, waste oils, bio-based oils, and blends with specialty polymers or additives. Some are purely softeners while others may be multifunctional. 

 

How is a bitumen softener introduced into the mix? 

Softeners can be added in the binder storage or feed tank, blended into the liquid binder stream, or injected upstream of the mixer. Some are compatible with in-plant systems. Others may require pre-blending or circulation protocols. 

 

Does adding a bitumen softener affect high-temperature (rutting) performance? 

If the softener reduces the binder stiffness too much, the mix may be more prone to rutting under heavy loads. Effective bitumen softeners balance low-temperature flexibility while helping to control high-temperature strength through proper dosing.  

 

Are bitumen softeners environmentally friendly? 

Bio-based bitumen softeners tend to be more sustainable than petrochemical solutions by reducing reliance on virgin petroleum blends and helping lower carbon footprint. By reducing viscosity, bitumen softeners may also contribute to lower fuel usage and reduced emissions during production. However, producers must check each bitumen softener for toxicity, leaching, VOC emissions, and compatibility with applicable environmental regulations. 

 

Do bitumen softeners leach out or degrade over time? 

A well-engineered softener should be compatible with the binder and remain stable over the pavement's life. Poor formulations might leach, volatilize, or degrade, which would erode performance over time. Long-term aging and durability testing are important to consider when selecting a bitumen softener. 

 

How is the effectiveness of a bitumen softener evaluated in the lab?  

Typical tests for bitumen softener evaluation include: 

  • Penetration 
  • Softening point 
  • Viscosity 
  • DSR (rutting/cracking parameters) 
  • Aging protocols (RTFO, PAV) 
  • Cracking tests (flexural, bending beam) 
  • Low-temperature performance (SEMB) 
  • Fatigue 

 

Can bitumen softeners replace virgin binder entirely? 

Bitumen softeners are not a replacement for virgin binder in an asphalt mix. Bitumen softeners generally supplement the existing binder to improve its functionality. Typical softener addition in formulas is less than 10 % by bitumen weight. They may reduce, but do not fully eliminate, the need for virgin binder.  

 

Are there compatibility or mixing issues for bitumen softeners with certain binder types? 

Compatibility depends on the base binder chemistry (source, oxidation level, additives) and the softener's chemistry. Some combinations may cause phase separation, instability, or poor performance. Proper compatibility testing and formulation are essential when choosing the right bitumen softener. 

 

What are the risks or downsides of using a bitumen softener? 

  • Over-softening leading to rutting or bleeding 
  • Poor long-term durability if softener degrades 
  • Potential incompatibility or instability 
  • Additional cost and process complexity 
  • Environmental or regulatory constraints 

 

How do you choose or specify a bitumen softener for a project? 

Key selection factors include: 

  • Compatibility with binder source(s) 
  • Proven performance in aging, cracking, rutting tests 
  • Supply, cost, handling, and logistics 
  • Environmental / regulatory compliance 
  • Technical support, blending compatibility, and track record 

 

Can bitumen softeners be used in both hot mix and warm mix asphalt? 

Many bitumen softeners are compatible with hot mix asphalt and warm mix asphalt technologies. In both applications, bitumen softeners can enhance workability and coating by reducing viscosity.  

 

Do bitumen softeners affect pavement compaction or workability? 

By reducing binder viscosity, bitumen softeners improve coating and compaction. This can lead to better density and smoother surfaces with less effort during laydown. 

 

 

Bitumen Softeners: ReNUBIT® and NuMIXER® 

Sripath Technologies offers two proven solutions for bitumen softeners. Both are formulated for to help producers manage or lower viscosity, improve polymer compatibility and dispersion, and enhance low temperature properties.  

 

ReNUBIT® is a special blend of petrochemical oils that supports high filler loadings and works as an effective cutter to control viscosity.  

 

NuMIXER® is a bitumen softener derived from a green blend of prime bio-based oils that exhibits exceptional dosage efficiency and supports a lower carbon footprint.  

 

To learn more, about bitumen softeners, ReNUBIT, and NuMIXER, contact info@sripath.com. Â