Electrically conductive asphalt for control of snow and ice accumulation. Paper presented at the 47th Annual Meeting of Highway Research Board, January 1968.

An asphaltic concrete made electrically conductive by the addition of graphite was designed and tested in small test plots over two winter seasons. Power dissipation per unit surface area was calculated. From the design requirements of 20 watts/square foot, 1/2-in thickness, 30 volt potential drop between electrodes spaced 5 ft apart, the necessary resistivity was calculated to be 1 ohm-inch. Laboratory studies to obtain this value were made, first using simulated asphaltic concrete (paraffin as a binder) and then asphalt-graphite-aggregate briquettes covering a wide range of mixtures. These studies led to the choice of a 25 percent graphite level, and six test sections were constructed at usa crrel using this mix and three thicknesses and sizes of electrodes. Actual resistivities were 7 to 12 times design value. Mixing, placement and control are critical in achieving satisfactory electrical properties. The test sections performed satisfactorily over a two-winter observation period. The sections were not trafficked and measurements of resistivity showed increases of 21 to 83 percent over an 18-month period. Safety considerations would probably make necessary an overlay, since a steel form placed on one test section and loaded by standing on it resulted in a 40 percent current increase. Cost of a conductive asphalt with electrodes would be competitive with other methods of heating pavement surfaces. /author/.