Abstract

Ground-up scrap tires have been used to modify asphalt binder for over 40 years. In that time the primary specification has been of an empirical nature. The primary specs have included particle size with time and temperature of blending. Some crude rotational viscosity measurements have been used to provide some quantification of properties. With the advent of the Superpave asphalt binder specifications efforts have been made to develop similar rheological tests for CRM asphalt binders. In this study the Bending Beam Rheometer and a new geometry using a Searle system for testing large particle size CRM is evaluated to determine if valid test results can be achieved for a PG type specification.

Testing using multiple size rubber particles in the new cup and bob geometry is evaluated. Evaluations are made using neat and polymer modified binders in the new geometry to compare to the standard DSR parallel plate geometry. Various sizes of CRM from 0.25 μm up to 1 mm are used to evaluate the new cup and bob geometry to determine if the results can be used for development of a PG type specification system. Full AASHTO M 320 Table 1 and MP 19 testing is done on all CRM binders in the study and from this data a proposed performance based CRM binder Superpave specification will be developed.

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