Sub-base course material

Materials used for the construction of the sub-base course can be unbound or hydraulically bound aggregates obtained by processing natural or manufactured or recycled materials. In the case of hydraulically bound sub-base, the binder is cement, lime or fly ash. 

In fact, sub-base materials are the same as base course materials. In some countries, sand-gravels are also permitted to be used for the construction of the sub-base course. 

More information about sub-base materials is given in Sections 10.5.1 and 10.5.2. 

The base course layer is positioned between the sub-base course (or subgrade, if there is no sub-base constructed) and the asphalt layers. Together with the asphalt layers, in a typical flexible pavement, it constitutes one of the main two structural elements of the pavement. The base course layer performs the following functions  

The base course consisted of a number of layers whose materials can be unbound aggregates or hydraulically bound aggregates. 

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