Viscosity-Temperature Effects of Polymer Modification as Depicted by Heukelom's Bitumen Test Data Chart

Abstract

Polymer modified bitumens (PMBs) have the ability to enhance a number of the performance properties of conventional bituminous binders. One aspect affected by the addition of a polymer to bitumen is the viscosity-temperature characteristics of the modified bitumen. This paper describes the assessment of the suitability of the Bitumen Test Data Chart (BTDC) and conventional binder properties at quantifying the viscosity-temperature characteristics of PMBs. The testing methodology that has been used in this investigation is to combine empirically-based test parameters (Penetration, Softening Point and viscosity) with fundamental rheological data measured with a dynamic shear rheometer (DSR). Two construction techniques, developed during the Strategic Highway Research Program (SHRP) and in the 1960s by Puzinauskas, have been used to convert the DSR parameters of complex viscosity, phase angle and strain rate to zero shear viscosity for incorporation in the BTDC. Results from the investigation indicate that although the BTDC can depict the advantages of polymer modification in terms of increased high temperature viscosity, the charts do not provide any additional information from that found in conventional viscosity-temperature plots. Although both the SHRP and Puzinauskas construction methods are able to calculate zero shear viscosities from DSR test data for penetration grade bitumens, only the Puzinauskas method is suitable for PMBs. The results also indicate that empirically-based binder tests, such as Softening Point, are not suitable at quantifying the performance of highly modified PMBs.

Keywords:

• Bitumen Test Data Chart
• Dynamic Shear Rheometer
• Polymer Modified Bitumen
• Viscosity