On the road construction materials, introduced two kinds: one is the white road surface of cement concrete, the two is black pavement asphalt mixture.
The two in terms of the audience, the latter used more, but on the composition and classification of asphalt mixture has been a headache for candidates, the following let Xiaobian for everyone to sort out.
Asphalt mixture is a kind of composite material, which is mainly composed of asphalt, coarse aggregate, fine aggregate and filler.
The varieties of road asphalt, soft asphalt and liquid petroleum asphalt, emulsified asphalt etc.. In the use of all kinds of asphalt, should be based on traffic, weather conditions, construction methods, asphalt surface type, material sources, etc.
When the asphalt is used in the multi layer surface, the upper layer should be made of thick asphalt.
Asphalt emulsion can be divided into quick coagulation, coagulation and coagulation of three according to the slow solidification rate, suitable for asphalt surface treatment, asphalt penetration pavement, normal temperature asphalt mixture layer and penetration layer, adhesive layer and seal.
According to the composition and structure of the material, it is divided into continuous gradation and discontinuous graded mixture. According to the aggregate gradation and the porosity is divided into dense, semi open graded and open graded mixture.
Most of the tests are divided into three types according to the principle of gradation, in which the suspension, the skeleton refers to the state of the coarse aggregate, and dense, the gap refers to the asphalt and content:
1 suspended dense structure
Continuous dense gradation asphalt mixture, due to the large number of fine aggregate, coarse aggregate, fine aggregate was squeezed out, therefore, the coarse aggregate in a suspended state located between fine aggregate. This kind of asphalt mixture has high compactness and poor stability. For the high grade highway in the dry area, the asphalt mixture can be used as the surface layer.
2 skeleton void structure
Because of the small quantity of fine aggregate, coarse aggregate is not only closely linked, but also has many voids. The inner frictional resistance of asphalt mixture of this structure plays an important role, therefore, the asphalt mixture is unaffected by the asphalt material, good stability.
3 skeleton dense structure
Gap graded asphalt mixture, is the organic combination of the above two kinds of structures. It is a rough set a certain amount of material to form a skeleton structure, and fine aggregate enough to fill the gap between the coarse aggregate of asphalt mixture, therefore, the structure of the density, strength and stability are good. At present, the structure of asphalt mixture pavement is still relatively small, in the research stage.