Bituminous mixtures – Hot mix asphalt type AC

Hot mix bituminous asphalt is a material widely used in the construction of pavements and wearing courses. It is composed of a combination of aggregates (gravel and sand), mineral filler, and bituminous binder. These components are heated and mixed at temperatures between 140 °C and 180 °C, ensuring a homogeneous mixture and optimal adhesion of the binder to the aggregates. This thermal process allows for efficient placement and compaction on site, resulting in a dense, continuous, and durable structure.

The behavior of the mixture is characterized by its resistance to repeated loads, durability against water action, and flexibility under thermal variations or subgrade settlements. Thanks to these properties, hot mix bituminous asphalts provide excellent performance on high-traffic roads. In addition, they are recyclable, allowing their reuse in new mixtures and helping to reduce the environmental impact associated with their production.

The production of hot mix bituminous asphalt is based on a careful selection of raw materials, each fulfilling a specific function to ensure a high-quality, long-lasting pavement:

• Aggregates (gravel and sand): They form the load-bearing structure of the mixture, providing stability, stiffness, and resistance to deformation under traffic loads. They also influence surface texture and friction, improving safety and skid resistance of the pavement.
• Filler: Composed of very fine mineral particles, it fills the voids between aggregates, enhancing internal cohesion, compaction, and mechanical stability of the mixture, as well as contributing to surface smoothness.
• Bituminous binder: This is the adhesive component that coats the aggregates and provides cohesion to the mix. It exhibits viscoelastic behavior, meaning it behaves as a viscous fluid at high temperatures (facilitating workability and compaction) and as an elastic solid at low temperatures (increasing stiffness and resistance to deformation). Its adhesiveness allows it to form a continuous film that ensures bonding with the aggregates and provides impermeability to the pavement. The properties of the binder are highly temperature-dependent, becoming less viscous and more deformable when heated, and stiffer and more brittle when cooled. Over time, the binder may age due to oxidation and the loss of volatile components, which increases its stiffness and brittleness, ultimately affecting pavement durability.