EVALUATION OF VISCOSITY-GRADED ASPHALT CEMENTS IN UTAH

The methods commonly used to grade asphalts (penetration, viscosity, and ductility) were investigated to determine their effectiveness as indicators of performance. Although these parameters were found to be of value in establishing asphalt quality and in controlling mix and lay-down properties, new methods are needed to better predict asphalt performance. A new procedure called force ductility has been correlated to performance. This modification in the standard ductility test measures the force in the asphalt sample versus elongation and is based on the theory that an asphalt must be able to relax as strain from traffic loading and temperature shrinkage is applied to a pavement. Asphalts with lower forces performed best in the field. Other tests found to be indicative of performance were temperature susceptibility, shear susceptibility, ductility versus temperature, and chemical fractionation.