Mathematical Relationships for Various Methods of Measurement of Bulk Specific Gravity of Hot-Mix Asphalt (05-2366)
Stacy Goad Williams, University of Arkansas, Fayetteville

Bulk specific gravity (Gmb) is a property that is used in virtually all aspects of design and production of asphalt pavements. Thus, it is imperative that the best possible method be used to determine this property. The SSD method has been used as the standard Gmb test method for many years. This method is believed to be accurate for fine-graded specimens, but it may not provide correct results for samples possessing a large number of sizeable surface voids. The recent increase in use of coarse-graded mixes has prompted the investigation of other tests to serve as viable alternatives to the SSD method. Because different test methods provide different Gmb values, changing to a new test method could seriously impact current asphalt design and production specifications. Until such changes are made, the ability to calculate an SSD measurement from the results of another method could allow the user to take advantage of the benefits of other test methods while alleviating the need to adjust current specifications. In this study, five test methods (SSD, height-diameter, CoreLok, CoreReader, and Kuss methods) were examined to determine factors affecting their results, and to determine potential relationships among methods. Test method, nominal maximum aggregate size (NMAS), and absorption values were determined to be significant factors affecting various Gmb measurement methods. Significant mathematical models were developed to translate Gmb values from the height-diameter and CoreLok methods to values as measured by the SSD method.