SOLVENT-FREE, NUCLEAR-FREE DETERMINATION OF ASPHALT CONTENT AND GRADATION OF HOT-MIX ASPHALT CONCRETE

A new method of analyzing hot-mix asphalt concrete has been developed that involves the pyrolysis or burn-off of the asphalt cement in a furnace. The method is simple and rapid, providing both asphalt content and aggregate gradation within about 1 to 1 1/2 h (substantial reductions in this time appear achievable). The method will permit elimination of solvent and nuclear techniques currently in use that have specific disadvantages and hazards. It can also be used, if desired, to supplement the nuclear gage, in which case burn-off will be used for gradation and the nuclear gage for asphalt content. Methods of performing the test, taking and analyzing data, etc., are described. Results based on aggregates and an asphalt cement widely used in the Chicago area are presented in derail. Further research is under way, and the questions that remain to be answered for the method to be standardized for widespread use are listed.