What Are The Different Mixes Of Asphalt And Why Do We Use Different Types?
Why do we use different types of Asphalt?
For an asphalt road's top layer, various asphalt mixtures are available. The type of surface course mixture selected will depend on the specifications for the road surface.
The top layer is typically referred to as the "surface course."
To provide an even profile for the user's comfort and at the same time have a texture to ensure adequate skid resistance, the surface course, which makes up the top layer of the pavement, must be able to withstand high traffic and environmental stresses without exhibiting unsatisfactory cracking and rutting.
In some situations, rapid surface water drainage through a porous surface is needed, whereas, in others, the surface course should be impermeable to prevent water from entering the pavement structure.
What are the different mixes of Asphalt?
The definitions provided in the European Asphalt Standards are the foundation for the descriptions of the asphalt mixtures that follow (EN 13108 series). The definitions used in the European Asphalt Standards are inverted commas in the text.
1. Asphaltic Concrete (AC) is an asphaltic material in which the aggregate particles are continuously graded or gap-graded to create an interlocking structure. The "basic" layer of the surface is frequently made of dense asphalt concrete.
2. Asphalt Concrete for Very Thin Layers (AC-TL) is "asphalt for surface courses with about a thickness of 20 mm to 30 mm, in which the aggregate particles are often gap-graded to establish a stone-to-stone contact and to provide an open surface texture."
3. Soft Asphalt (SA) "Combination of soft bitumen grades with aggregate." The Nordic nations employ this adaptable combination for secondary roads.
4. Hot Rolled Asphalt (HRA) is a "dense, gap-graded bituminous mixture" where the performance of the deposited material is greatly influenced by the mortar of fine aggregate, filler, and high-viscosity binder. A Hot Rolled Asphalt surface course will always include coated chippings, essentially single-size aggregate particles with a strong resistance to polishing that are thinly coated with high viscosity binder.
5. Stone Mastic Asphalt (SMA) is described as a "gap-graded asphalt mixture using bitumen as a binder, made of a coarse crushed aggregate skeleton bound with a mastic mortar" When a high level of stability is required, this mixture is frequently utilized as a surface layer. Additionally, the surface structure provides effective noise-canceling qualities.