The US Strategic Highway Research Program (SHRP) has developed binder specifications which require measurements with a dynamic shear rheometer (DSR). However, precision data for DSR measurements are limited and measurement methods have generally not been standardised. This paper investigates two important sources of error: accurate temperature control and appropriate test geometry selection. Key results were: (a) 1 degree C temperature difference resulted in significant variations in measured binder properties; (b) 20mm and 25mm parallel plate geometries had upper stiffness limits of 10 (super 5) Pa (gap 0.5-2mm); for the 8mm plate this increased to 10 (super 8) Pa and greater stiffnesses are affected by machine compliance. DSR test methods must be carefully defined to encompass such findings and other sources of error (sample preparation, equipment calibration etc). (A)
Samenvatting