Section IV: composition and materials of asphalt mixture (1) -- structure composition and classification

1、 Structure composition and classification

（1） Material composition ：

• Asphalt mixture It's a composite material , Mainly by asphalt 、 Coarse aggregate 、 Fine aggregate 、 kuangfen form , Some even joined polymer and Lignocellulose Mixed ; These materials of different quality and quantity are mixed to form different structures , And have different Mechanical properties .
• Mechanical strength of asphalt mixture , It is mainly composed of Intimal resistance and Impaction force , And the asphalt binder and its relationship with mineral aggregate Adhesion What constitutes a .

（2） Basic categories ：

• According to material composition and structure Continuous grading 、 Discontinuous grading ;
• According to the composition of mineral aggregate gradation and the size of voids, it can be divided into Dense distribution 、 Semi open grading 、 Open grading ;
• According to the maximum particle size of the project, it can be divided into Extra thick 、 Coarse grained 、 Medium grain 、 Fine grained 、 Gravel type ;
• According to the production process, it can be divided into Hot mix asphalt mixture 、 Cold mix asphalt mixture 、 Recycled asphalt mixture etc. .
  （3） Structure type
  It can be divided into Crowding principle Form and press Dense grading The two structural types formed by the principle .
  Press Grading principle Asphalt mixture composed of , Its structural composition usually has the following three forms ：
• suspension - Dense structure ： The structure has large cohesion , But the inner membrane resistance is small , Poor high temperature stability .AC Type a asphalt mixture is a typical representative of this structure .
• skeleton - Void structure ： The friction angle of the structure is high , But the cohesion is low . Asphalt macadam mixture （AM） and OGFC Drainage asphalt mixture is a typical representative of this structure .
• skeleton - Dense structure ： The structure not only has a high internal friction angle , The cohesion is also high , It is a structure that combines the above two structures . Asphalt mastic mixture （SMA） It is a typical representative of this structure .

2、 Main materials and properties

Urban road surface should be Give priority to A Grade bitumen , Coal tar pitch should not be used （ Toxic ）.
（1） Cohesiveness ： Asphalt material under the action of external force , The asphalt example produces the ability to resist deformation by mutual displacement, that is, the viscosity of the asphalt . Commonly used is conditional viscosity . When meeting high 、 Low temperature performance requirements , The requirements for high temperature performance shall be limited .
（2） Temperature sensitivity ： It refers to the sensitivity of the viscosity of asphalt materials to temperature . One of the indicators is the softening point , That is, the conditional temperature when the asphalt reaches a certain viscosity under specific test conditions . Asphalt with high softening point shall be selected for high-grade roads .
（3） Durability ： Have enough anti-aging performance , Make the asphalt pavement have a long service life . The film oven heating test is used to reflect its aging resistance . By boiling , Determination of adhesion of bitumen to aggregates , Reflect its ability to resist water damage , The higher the rank , The better the adhesion .
（4） plasticity ： The ability to deform without being damaged by external forces , namely The ability of reactive bitumen to resist cracking .10℃ or 15℃ Ductility . It is generally believed , Low temperature ductility the greater the ductility , The better the cracking resistance . Low or high temperature in winter 、 Areas with large temperature difference , Asphalt with large low temperature ductility is required .
（5） Security ： The flash point test is used to determine the flash fire temperature of asphalt – Flash point , Determine its safe use range . The softer the Asphalt （ The label is high ）, The lower the flash point .