Electrically conductive pavement mixture

Abstract

An electrically conductive paving system that has enhanced conductivity of the conductive graphite/asphalt layer. This is achieved by incorporating into the paving mixture a blend of two naturally occurring crystalline flake graphites, one being coarse (generally larger than 40 mesh/425 microns) and the other being fine (generally smaller than 100-200 mesh/150-75 microns). The ratio of course flake graphite to fine flake graphite may be from 1.5:1 and 1:1.5, but is preferably approximately 1:1.

1. An electrically conductive paving mixture comprising:
 an aggregate fraction; 
 a bituminous fraction; and 
 a fraction of blended natural flake graphite, the blended natural flake graphite comprising a coarse portion of which is greater than 425 microns in size and a fine portion of which is less than 200 150 microns in size, the coarse portion and the fine portion being combined in a ratio of between 1.5:1 and 1:1.5 and comprising 10-25 percent by weight of the paving mixture. 
 
     
     
       2. The electrically conductive paving mixture of  claim 1  wherein at least 95 percent of the coarse portion is smaller than 850 microns and at least 80 percent of the coarse portion is larger than 500 microns, while at least 80 percent of the fine portion is smaller than 150 microns. 
     
     
       3. An electrically conductive pavement system comprising:
 a grid of electrically conductive cables, 
 an electrically conductive paving mixture covering and surrounding the grid; the paving mixture having an aggregate fraction, a bituminous fraction, and a fraction of natural flake graphite comprising a coarse portion of which is greater than 425 microns in size and a fine portion of which is less than 200 150 microns in seizes size, the coarse portion and the fine portion being combined in a ratio of between 1.5:1 and 1:1.5 and comprising 10-25 percent by weight of the paving mixture; and 
 an asphalt-impregnated fabric encapsulating the conductive pavement. 
 
     
     
       4. The electrically conductive pavement system of  claim 3  wherein the coarse portion and the fine portion of the graphite fraction are combined in a 1:1 ratio. 
     
     
       5. The electrically conductive pavement system of  claim 3  wherein at least 95 percent of the coarse portion is smaller than 850 microns and at least 80 percent of the coarse portion is larger than 500 microns, while at least 80 percent of the fine portion is smaller than 150 microns.