Volume 4, Issue 8 (September 2007)
Specifications for Roofing and Industrial Asphalts Using Dynamic Shear Rheometry (DSR)
Asphalt specifications in the U.S., Europe, and elsewhere in the world are increasingly dependent upon basic principles of rheology, in particular dynamic shear rheology (DSR). The roofing industry would be benefited by a revised ASTM specification featuring DSR measurements as opposed to the current ASTM Standard Specification D 312 in which softening point is the primary distinguishing characteristic of roofing asphalts. Rheological performance is the critical determinant of satisfactory roofing asphalt quality in that it must possess sufficient stiffness at higher temperatures to resist slippage on slopes and also be flexible enough at lower temperatures to resist cracking and debonding. This paper demonstrates the use of rheological parameters to replace the current softening point parameters, as well as introduces high and low temperature rheological parameters for climatic consideration. The proposed change incorporates climatic performance grades with high and low temperature limits which are based on DSR testing for the basic types of roofing asphalt.