Characterizing Asphalt Volatility

Asphalt volatility is one of several factors that can affect the degree of environmental discharge and worker fume exposure that occurs during hot-mix manufacturing and construction. Fundamental volatility measurements using vapor pressure generally are not practical for asphalt because of its low volatility. Eight potential asphalt volatility tests were considered: thin film oven test, rolling thin film oven test, Cleveland open cup flash point, steam distillation, thermogravimetric analysis, German rotating flask test, vacuum flask distillation, and high-temperature simulated distillation by gas chromatography. Many of these tests are affected by testing artifacts such as oxygen addition, skin formation, and thermal degradation. The procedure, standardization, and validity of each test are discussed. Existing data are reviewed and new data are presented to demonstrate the relationships among these tests. On the basis of available information, it is concluded that the best empirical (condition-dependent) volatility test is the German rotating flask test conducted with an inert gas, and the best compositional (conditionindependent) volatility test is high-temperature simulated distillation by gas chromatography.