The Asphalt

THE ASPHALT.

Asphalt exists in various forms over widely distributed parts of the earth, and has been in somewhat common use for different purposes since the dawn of history; con sequently the terms employed to designate it have been varied, and recently there has been no little confusion in the nomenclature, due in no small part to conflicting commercial interests. The following definitions are believeil to be generally accepted, and are suffi ciently exact for present purposes.

Bitumen. A natural hydro-carbon mixture of mineral occurrence, widely diffused in a variety of forms which grade by imperceptible from a light gas to a solid, sometimes found in a pure state but usually intermixed with organic and inorganic matter. The bitumen series includes the following, in order of their density: natural gas, natural naptha, petroleum, maltha (at ordi nary temperatures soft and sticky), asphalt (at ordinary tempera tures stiff and non-sticky), glance pitch (dry and brittle).

Asphalt. A general name for the solid forms of natural mineral bitumen. Asphalt is distinguished from coal in being soluble in bisulphide of carbon and in benzole. Coal, peat, etc.. are called pyro-bitumens because they yield an artificial bitumen by distillation. Asphalt is usually found associated with various mineral and organic substances. Asphalt is sometimes popu larly called mineral pitch and mineral tar: and different varieties of asphalt are called grahamite, albertite, gilsonite, wurtzelite, uinta tite, turrellite, etc.

The term asphalt is the English equivalent of asphaltum. the Latin form. Asphalt and bitumen are frequently used synony mously, but usually in paving literature bitumen is employed to designate the valuable hydro-carbon compounds in the native asphalt.* Crude Asphalt.The native mixture of bitumen, sand, clay, water, organic matter, etc.

Refined Asphalt.

The native mixture after it has been freed wholly or in part from water and organic and inorganic matter by being heated. Commercial refined asphalt contains considerable earthy matter; in fact commercial refining consists virtually in driving off the water and volatile oils, and incidentally in removing a little earthy matter.

Rock Asphalt.

A limestone or sandstone naturally im pregnated with asphalt. Rock asphalt is the principal form of asphalt used in Europe for paving purposes, and is usually there designated as asphalt. Some European commercial interests insist that only rock asphalt is entitled to be called asphalt.

Asphaltic or Bituminous Limestone. A limestone natu rally impregnated with asphalt.

Asphaltic or Bituminous Sandstone. A sandstone natu rally impregnated with asphalt.

Compressed Asphalt.

In Europe, particularly in France, a rock-asphalt pavement is frequently referred to as being made of compressed asphalt, or, in French, asphalte comprime.

Asphalt Mastic. A term frequently applied to refined asphalt, particularly to that obtained from bituminous rocks, and is usually in the form of cakes, which are melted and mixed with sand and used for making pavements and sidewalks, chiefly the latter (see § 919).

Asphaltic Cement. Refined asphalt which has been mixed with some solvent to increase its plasticity, adhesiveness, and tenacity.

Asphalt Pavement.

A pavement composed of sand or pulverized stone held together by asphalt. In America an asphalt pavement is ordinarily understood to be a comparatively thin layer of sand held together by asphalt laid upon a bed of hydraulic cement concrete; but in Europe the term asphalt pavement is understood to be a comparatively thick layer of asphaltic lime stone or asphaltic sandstone, with or without a hydraulic concrete base.

Asphaltic Concrete. Broken stone bound together with asphaltic cement.

Asphalte Comprime.

The French equivalent of corn pressed asphalt—see § 576. This term is employed to indicate that the material is compressed in place, in contradistinction to being simply applied with a trowel.

Asphalte Coute. The French equivalent of asphaltic mastic—see § 577. It is applied with a trowel without other com pression.