114 HIGHWAY CONSTRUCTION 



The burning of leaves or making of fires on asphalt pavements 

 should not be permitted, as it injures the asphalt, and the paving com- 

 panies cannot be compelled to repair the damaged places without 

 compensation. 



Asphalt Blocks. Asphalt paving blocks are formed from a mix- 

 ture of asphaltic cement and crushed stone in the proportion of 8 to 12 

 per cent of cement to 88 and 92 per cent of stone. The materials are 

 heated to a temperature of about 300 F., and mixed while hot in a 

 suitable vessel. When the mixing is complete, the material is placed 

 in moulds and subjected to heavy pressure, after which the blocks are 

 cooled suddenly by plunging into cold water. 



The usual dimensions of the blocks are 4 inches wide, 3 inches 

 deep, and 12 inches long. 



Foundation. The blocks are usually laid upon a concrete founda- 

 tion with a cushion-coat of sand about J inch thick. They are laid 

 with their length at right angles to the axis of the street, and the longitu- 

 dinal joints should be broken by a lap of at least 4 inches. The blocks 

 are then either rammed with hand rammers or rolled with a light steam 

 roller, the surface being covered with clean, fine sand ; no joint filling is 

 used, as, under the action of the sun and traffic, the blocks soon become 

 cemented. 



The advantages claimed for a pavement of asphalt blocks over a 

 continuous sheet of asphalt are: (1) That they can be made at a 

 factory located near the materials, whence they can be transported to 

 the place where they are to be used and can be laid by ordinary paviors, 

 whereas sheet pavements require special machinery and skilled labor; 



(2) that they are less slippery, owing to the joints and the rougher 

 surface due to the use of crushed stone. 



Asphalt Macadam Bituminous Macadam. Recently it has been 

 proposed to use asphalt as a binding material for broken stone. 

 There are two patented processes the Whinery and the Warren 

 which differ slightly in details. 



The advantages claimed for these methods are: (1) The first 

 coat will be materially less; (2) it will offer a better foothold for horses; 



(3) it will be at least as durable as the ordinary sheet asphalt; (4) it will 

 not shift under traffic and roll into waves; (5) it will not crack; (6) it 



