What are Asphalt Additives?
They are substances added in small quantities to asphalt cement or cutback asphalt to improve their physical and chemical properties. Asphalt cement is a highly sticky and thick liquid that is produced by refining crude oil. Asphalt additives help modify the properties of asphalt cement according to the requirements of road construction projects.
Types
Some major types of it used in road construction are:
Anti-strip Additives
Asphalt Additives help reduce stripping of asphalt from aggregate in the pavement. Stripping occurs when moisture in the pavement pores causes adhesion failure between asphalt cement and aggregate. Anti-strip additives create a bond between aggregate and asphalt cement preventing stripping.
Viscosity Modifiers
Viscosity modifiers enhance the high-temperature performance properties of asphalt binders. They help improve resistance to permanent deformation in hot weather conditions. Viscosity modifiers improve rutting resistance and reduce thermal cracking of pavements.
Polymer Modifiers
Polymer modifiers are usually thermoplastic polymers added to asphalt cement to enhance its elastic recovery and stiffness properties. Common polymers used are styrene-butadiene-styrene, styrene-butadiene rubber and ethylene vinyl acetate. Polymer modified asphalt binders exhibit higher resistance to reflective cracking, thermal cracking and rutting of pavements.
Anti-Oxidants
Anti-oxidant additives protect asphalt binders from premature hardening and aging due to oxidation during storage, transportation and pavement construction activities. Oxidation causes asphalt to become brittle over time losing its viscous and ductile properties. Anti-oxidants increase the service life of asphalt pavements.
Usage of Asphalt Additives in Pavement Construction
They play an important role in improving the quality and performance of hot mix asphalt used for pavement construction. Some key uses of it in roads are:
– Preventing Moisture Damage
Anti-strip additives are essential to overcome stripping in asphalt concrete. They improve adhesion between aggregate and asphalt binder creating a moisture-resistant pavement.
– Enhancing High Temperature Performance
Viscosity modifiers and polymer modifiers Asphalt Additives increase the softening point of asphalt allowing it to hold up better to traffic loads in warm weather conditions. They improve resistance to rutting and thermal cracks.
– Combating Reflection Cracks
Polymer modified asphalt is mainly used as a wearing course or stress absorbing membrane interlayer to reduce reflective cracking from cracks in underlying layers.
– Tack Coats
Asphalt emulsions containing tackifying resins or polymers are used as tack coats between pavement layers to bond them together preventing delamination.
– Preventing Early Hardening
Anti-oxidant additives increase the shelf life and service period of asphalt by protecting it from premature oxidation during storage, transportation and paving activities.
Benefits
The use of suitable asphalt additives provides significant benefits in terms of pavement performance and life cycle costs. Some key benefits are:
– Improved Durability: Additives enhance the durability of asphalt pavements by improving resistance to moisture damage, rutting, thermal and load-induced cracking.
– Lesser Maintenance: Durable asphalt roads made using additives require lesser maintenance activities like crack sealing and patching during their design life.
– Smooth Ride: Asphalt mixes prepared with additives provide better riding quality by resisting rutting in warm seasons and reflective cracking from underlying layers.
– Cost Savings: They initially increase the material cost but provide long-lasting roads needing rehab and rehabilitation much later resulting in economic savings over the life cycle.
– Environment Friendly: Greenhouse gas emissions are also reduced as the pavement requires less frequent reconstruction attributable to enhanced durability from additives.
Choosing Right Asphalt Additive
For obtaining optimal benefits, it is important to select the type and correct dosage rate of it based on:
– Project requirements like traffic loading, climatic conditions, material properties
– Specifications and guidelines provided by agencies for different pavement layers
– Recommendations from additive manufacturers backed by laboratory test results
– Experience with performance of different additive technologies in similar projects
Standard tests are conducted to evaluate properties like viscosity, toughness, adhesion, moisture resistance etc. of modified asphalt and validate the choice of additive and dosage. Third party certification also provides quality assurance.
Conclusion
Asphalt additives play a key role in improving the performance of asphalt pavements. When properly selected and dosed, they provide long-lasting, economical and environment-friendly roads by enhancing strength, flexibility and durability properties of asphalt binders and mixes. Additives facilitate technological advancements in asphalt technology for sustainable infrastructure development.
*Note:
1. Source: Coherent Market Insights, Public sources, Desk research
2. We have leveraged AI tools to mine information and compile it.