Originally, a 1969 study by Antrim and Busching suggested that asphalt binder content of HMA samples could be determined by an “ignition method” that involved the virtual complete combustion of asphalt binder at a high temperature. This method eliminates the need for the chlorinated solvents used in solvent extraction methods. Asphalt binder content is then calculated by subtracting the mass of the aggregate remaining after the asphalt binder is burned off from the initial mass of the test sample. The ignition method of determining asphalt binder content allows for the asphalt binder in an HMA sample to be burned off in an oven (Figure 2) at temperatures above the flame point of the binder. The nuclear method uses a nuclear source and detector to determine the asphalt binder content. These methods also produce aggregate on which a gradation test can be performed. The before and after masses are then compared to determine asphalt binder content. Solvent extraction methods are used to separate then remove the constituent asphalt binder from the aggregate. There are several methods used to determine HMA asphalt binder content. HMA that has too little asphalt binder can have lowered fatigue resistance and problems with raveling and stripping. HMA that has too much asphalt binder can experience problems such as bleeding, lowered skid resistance, and lowered resistance to permanent deformation (rutting and shoving). Quantitative determination of the asphalt binder content of HMA mixtures and pavement samples is necessary for many reasons, including: quality control, specification acceptance, and mixture evaluation studies. Maximum theoretical specific gravity sample.
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