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Dispersion of submicrometre-size carbon black particles in asphalt at dosages of 11 to 16 percent by weight of asphalt has been found to improve the asphalt properties of durability, wear resistance, and temperature-viscosity susceptibility. This concept of reinforcing asphalts with a carbon black filler has been made practical by pelletizing the carbon black with a high-durability maltenes binder compatible with asphalts. The pellets are packaged in 11.34-kg (25 lb) polyethylene bags which are introduced, bag and all, into hot-mix cycle of asphalt concrete batch-type plants. In continuous-type plants, the pellets are added either through the asphalt feedline in correct proportion to the hot asphalt or through the hot aggregate feed in correct proportion to the hot aggregate.
Since the carbon black becomes part of and bulks the asphalt, adjustments are made in batch weights to keep the volume relationship of binder to rock constant. Other design considerations are discussed.
Effects of the carbon black addition on the properties of asphalts and asphalt concrete, as measured in both laboratory and field experiments, are shown. The present status of a continuing program of field testing and evaluation is described.
carbon black filler, asphalt, asphalt concrete, asphalt reinforcing agent, asphalt modifier, wear resistance, durability, temperature-viscosity susceptibility, tender pavements, stiffness, low-temperature cracking, high-temperature distortion, asphalt migration, bleeding
Consulting civil engineer, Oakland, Calif.
Manager, Applications Development, Cabot Corp., Boston, Mass.