Asphalt pavement layer by surface layer, base, sub-base, mat layers. Asphalt layer in asphalt pavement itself, belongs to the category of flexible pavement, but its base in addition to flexible materials, cement concrete or rigid or semi rigid hydraulic material.
Surface is directly under the wheel load repeatedly and natural factors affecting the structure of layers by 1~3 layer. Should be set according to the requirements of the surface layer sliding wear resistance, density and stability of asphalt layer in the surface layer, the layer should be based on the following highway, asphalt layer thickness, climatic conditions, selecting the appropriate asphalt structural layers. 
Base is set below the surface, and, together with surface wheel loads repeatedly spreading grass-roots, mat layer, soil, level playing a mainly supporting role. Indicators of the strength of the base material should have higher requirements. Primary highway or traffic needs to set one or two layers. When grass-roots thick required two-layer construction, respectively, called on the grass-roots level, grass-roots units.