Why are special PMA or ARB binders used in friction course mixes?

Special PMA (Polymer-Modified Asphalt) or ARB (Asphalt-Rubber Binder) binders are utilized in friction course mixes primarily to enhance performance and durability. These binders are engineered to provide superior resistance to aging, cracking, and rutting, which are critical factors for the longevity of road surfaces exposed to various environmental and traffic conditions.

PMA binders incorporate polymer additives that improve the elasticity and viscosity of the asphalt, allowing it to better accommodate thermal expansions and contractions. This quality is particularly important in friction courses, which need to maintain performance under heavy loads and varying temperatures. Similarly, ARB binds reclaimed rubber from tires into the asphalt, providing additional flexibility and resilience.

By improving the overall performance characteristics of the asphalt mix, these binders help ensure that the pavement can withstand the rigors of traffic and environmental influences over a prolonged period, minimizing maintenance needs and ensuring safer driving conditions.