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Fig. 1 A modern asphalt concrete highway. Shoulder striping is used as a safely feature.

Fig. 2 Asphalt concrete at the San Francisco International Airport. They are used when high wheel loads and high volumes of traffic occur and are, therefore, often designed for a particular installation. 2 . Theory of asphalt concrete mix design High types of flexible pavement are constructed by combining an asphalt cement, often in the penetration grade of 85 to 100, with aggregates that are usually divided into three groups, based on size. The three groups are coarse aggregates, fine aggregates, and mineral filler. These will be discussed in detail in later chapter. Each of the constituent parts mentioned has a particular function in the asphalt mixture, and mix proportioning or design is the process of ensuring that no function is neglected. Before these individual functions are examined, however, the criteria for pavement success and failure should be considered so that design objectives can be established. A successful flexible pavement must have several particular properties. First, it must be stable, that is to resistant to permanent displacement under load. Deformation of an asphalt pavement can occur in three ways, two unsatisfactory and one desirable. Plastic deformation第 2 页 共 12 页