These materials can be used in various forms to waterproof, protect, or rein- 

 force a structure. Table 25 shows how each type of asphalt material may be 

 used to perform these various functions. 



(2) Impermeable Asphalt Concrete Linings . Impermeable asphalt 

 mixes are similar to asphalt mixes for highway paving except that, since a 

 low void content mix is required to ensure impermeability, they usually 

 have higher mineral filler and asphalt-cement contents. Also a harder, or 

 more viscous, grade of asphalt cement normally is used. Mixes are prepared 

 in an asphalt mixing plant and placed with conventional, or as shown in 

 Figure 41, special paving equipment. Compaction during paving is necessary 

 to produce the required impermeability. 



Figure 41. Roller operated by a dragline compacts the asphalt 

 revetment, San Joaquin River, California [photo 

 courtesy of ACI)_. 



The primary purpose of impermeable asphalt mixes is to waterproof 

 hydraulic structures. Watertight linings are used to impound water in 

 reservoirs, ponds, and lagoons; to waterproof dams, dikes, and embankments; 

 and to prevent seepage losses in canals and channels. They are most often 

 used as surface linings, since they are resistant to wave action and the 

 erosive effects of water currents. 



Revetments constructed with impermeable asphalt mixes are used for bank 

 protection on streams, reservoirs, lakes, and shorelines. Waterproofing 



75 



