loose material. Its temperature should preferable exceed 38 Celsius (100 

 Fahrenheit). A sloped surface usually necessitates hand spraying. This 

 should be done in a back-and-forth sweeping motion to build up the film and 

 to keep the asphalt from flowing down the slope. 



(c) Asphalt Mastic Seals . In addition to providing a seal, 

 asphalt mastics applied to the surface of asphalt linings provide protection 

 from mechanical abuse. Asphalt mastics, generally placed on an asphalt 

 lining with a screed, permit a heavier coating than sprayed applications, 

 and well-designed mixtures can make the surface resistant to abrasion by 

 waves, or scouring by waterborne sands. Asphalt mastic mixtures for this 

 purpose are essentially blends of mineral filler and asphalt cement. 



(d) Prefabricated Asphalt Panels . The typical prefabricated 

 asphalt panel consists of a core of ductile, blown or oxidized asphalt 

 (asphalt which has certain natural characteristics changed by blowing air 

 through it at elevated temperature) fortified with mineral fillers and 

 reinforcing fibers. The ingredients are blended and molded under heat and 

 pressure. The core is then sandwiched between protective sheets and a 

 protective coating of hot-applied asphalt cement. The protective sheets may 

 be an asphalt-impregnated felt, or plasticized or flexible glass fabrics 

 (Fig. 46). 



Figure 46. Lining ditch with prefabricated 

 asphalt panels. 



Asphalt panels are usually about 13 millimeters (1/2 inch) thick, but 

 they are available as thin as 3 millimeters (1/8 inch) thick. They are 

 usually 1.0 to 1.2 meters (3 or 4 feet) wide and 3 to 6 meters (10 to 20 

 feet) long for handling and placing. 



81 



