Classification of asphalt concrete.
a) Asphalt concrete for the construction of road layers is prepared by hot mixing of filler materials (ballast, granule, sand and mineral powder) with bitumen binder
b) According to the size or fineness of the aggregate material used for the production of asphalt concrete, it is classified:
-granular asphalt concrete with grain size up to 35mm.
-medium asphalt concrete with granule size up to 25mm.
-fine asphalt concrete with granule size up to 15mm.
-sand asphalt concrete with grain size up to 5mm.
c) Depending on the porosity contained in the asphalt concrete mass in the compacted state is divided:
– Compacted asphalt concrete, which is prepared with crushed ballast and granule in a mass of 35 to 40%, sand 50% and mineral powder 5 to 15% and after compaction has a residual porosity of 3 to 5% by volume.
– Porous asphalt concrete (binder) that is prepared with 60 to 75% broken ballast, 20 to 35% sand and that after compaction has a residual porosity of 5 to 10% by volume.
d) Compacted asphalt concrete is used in the construction of the user layer, while porous concrete is used for the binder layer.
e) Compacted asphalt concrete depending on the content of mineral powder expressed in percentage by weight and the qualities of its constituent materials, are classified into two categories:
-Category I with 15% mineral powder content
-Category II with 5% mineral powder content
Determination of asphalt concrete composition
a) The category, type, thickness of the layer and the technical requirements of asphalt concrete are determined by the designer and given in the project implementation, while the composition for the production of asphalt concrete, which expresses the ratio between its constituent elements (ballast or crushed gravel, granule, sand, powder mineral and bitumen) as well as technical indicators of the mass of asphalt concrete in the compacted state, are determined by laboratory tests.
Below you must watch a video of the application and compaction of asphalt: