Elaine Goosen, Stellenbosch University
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As performance grades are developed for South African bituminous binders, the need arises to expand the related engineering knowledge and understanding in the context of local technology and materials. The Dynamic Shear and Bending Beam Rheometers are commonly applied to evaluate fundamental viscoelastic material behaviour by measuring properties such as the shear complex modulus and phase angle. The isotherms are subsequently shifted to form master curves and Black Space diagrams. Focusing on high, intermediate and low-temperature load-displacement responses, examining these behavioural curves leads to the identification of primary stiffness and relaxation ranges. Changes and the evolution of parameters in response ranges can indicate ageing-related developments in binder rheology. The progression of binder rheology may vary significantly depending on the modification, seal type and origin of the binder. For various seal binders, performance-related testing is conducted. The principles and modelling of shift and master curves are reviewed as an introduction to the influences on and development of rheology with increased age. The implications of these changes are discussed with regard to expected performance. An overview of current research is presented.
