Asphalt used as a superstructure material, is a mixture of mineral coarse and fine aggregate and bituminous binder with adhesive properties. The bitumen binder content typically ranges from 3% to 7% depending on the mixture and application.
Aggregates used in asphalt road mix are hard minerals that are selected according to their physical properties and dimensions depending on the mix design. These minerals may be of natural origin such as crushed stone, gravel and sand, or artificial, such as blast furnace slag.
Bitumens are viscous hydrocarbons obtained from the distillation of crude oil. Bitumens are produced in different grades according to their specific engineering and physical properties in relation to their viscosity, hardness or brittleness at a given temperature. Bitumens are sometimes modified with polymers to improve performance over a wide temperature range served by asphalt mixtures.
The most important physical quality of bitumen is that it softens and becomes more fluid when heated and hardens again when cooled. Thermoplastic behavior. Asphalt road construction and laying is typically done in the temperature range of 140 ° C to 160 ° C. Another important feature of the bitumen is that it acts as a solid at normal air temperature, but has viscous viscosity and viscoelastic properties under load. This means that it can adapt to movement from the asphalt base, and microscopic cracks under traffic can automatically close.
Different asphalt mixing formulas or recipes are used in various asphalt applications. These formulas are designed in accordance with the cost and service life targets of asphalt road owners.