How are sand and gravel produced and used in road building?
Sand (fine aggregate) and other rock material (course aggregate) are produce from quaries. The basic purpose of a quarry is to remove sound rock from the face of the quarry by blasting, then using a series of crushers, pulverizers, and screening units to produce and seperate various sized aggregate. Asphalt cement is a dark brown to black cementitious material that is either naturally occuring or is produced by petroleum distillation. Asphalt cement is one of the oldest engineering materials used by man. It has been known to have been used as far back as 6000 BC in ship building applications in Sumeria. Almost all of the asphalt cement used in the US today is obtained by processing crude oils. Following the discovery of the petroleum refining process in the early 1900’s and the popularity of the automobile, large quantities of petroleum asphalt were processed by the oil companies. Gradualy these refined aphalts became plentiful and of good quality. This forced the natural asphalts into
