精选优质文档-倾情为你奉上第二课沥青及沥青混合料Asphalt $ Mix AsphaltText: Asphalt &Asphalt Paving Materials1 Asphalt DefinedThe black cementing agent known as asphalt has been used for road construction for centuries. Although there are natural deposits of asphalt , or rock asphalt , most used today is produced during the refining of crude oil. Asphalt is a constituent of most petroleums and is isolated through the refining process.Asphalt is called a bituminous material because it contains bitumen,
