most important function is as a waterproof barrier holding water 

 or other liquid inside the structure. 



(7) Asphalt Mastic . A mixture of mineral aggregate, mineral 

 filler and asphalt in such proportions that the mix can be applied 

 hot by pouring or by mechanical manipulation; it forms a voidless 

 mass without being compacted. 



(8) Asphalt Mattress, Slab . Terms, according to size, denoting 

 prefabricated flexible units composed of an asphalt mastic mixture 

 reinforced with mesh, netting, lines, or cables as required. 



(9) Asphalt Membrane . A relatively thin layer of asphalt formed 

 by spraying a high-viscosity, high softening point asphalt cement in 

 two or more applications over the surface to be covered. It is 

 normally about 6 millimeters (1/4 inch) thick and is used for water- 

 proofing or sealing. It is buried to protect it from weathering and 

 physical damage. 



(10) Asphalt Mat . A felt or fabric sheet impregnated or 

 coated with asphalt to form a watertight lining or membrane usually 

 6 millimeters or less in thickness. It may be a sheet that is first 

 installed in place with the asphalt applied following installation, 

 or it may be a finished material that is watertight and ready for 

 installation. 



(11) Asphalt Revetment . A protective asphalt facing on a 

 sloped surface, usually placed for the purpose of protecting an 

 embankment from erosion. Revetments may or may not extend all the 

 way to either the toe or crest of the sloped embankment. The term 

 subaqueous refers to that part of a revetment placed under the 

 surface of the water. Upper bank paving is that part placed above 

 the surface of the water. 



(12) Impermeable Asphalt Mixes . Asphalt mixes having low 

 voids, (usually less than 4 percent) after installation, designed 

 to prevent the passage of water. 



(13) Porous Asphalt Mixes . Asphalt mixes that permit the free 

 flow of water through the mix. Porous asphalt mixes are divided 

 into two general classifications: permeable asphalt mixes and 

 open-graded asphalt mixes (see below) . 



(14) Permeable Asphalt Mixes . Asphalt mixes having medium 

 voids after installation, designed to permit the free passage of 

 water through the lining to and from the supporting layer or 

 embankment . 



(15) Open-Graded Asphalt Mixes . Asphalt mixes having high 

 voids, designed to provide a free drainage layer underneath an 

 impermeable lining. 



167 



