Investigation of Asphalt Mixture Creep Compliance at Low Temperatures

ABSTRACT The creep compliance is one of the main material characteristics used to describe low temperature behavior of the asphalt mixtures. It also serves as a primary input to the current thermal cracking model in the US that is used to predict thermally induced cracking in asphalt pavements over their service life. The current standard method in the US to determine creep compliance of asphalt mixtures is the Indirect Tensile (IDT) test. This paper investigates the feasibility of using the Bending Beam Rheometer (BBR) device to determine the low-temperature creep compliance of thin asphalt mixture beams (127x12.7x6.35mm). The BBR was used to evaluate 20 different asphalt mixtures and the results were compared with the standard IDT results. Direct comparison of the BBR and the IDT results indicate that both methods produce slightly different creep compliance curves and the relative ratio between the BBR and the IDT results varies with time and temperature. A simple phenomenological relation was proposed that gives good predictions of the IDT results based on the BBR creep compliance. Furthermore, short-term aged asphalt binders used in the mixtures were also tested in the BBR. Modified Hirsch model was applied to the BBR results on both mixtures and binders and it was shown that this model is capable of producing quite accurate results in forward and inverse predictions using considered dataset. It was concluded that the BBR can be used in practical and surrogate estimation of the mixture creep compliance but proposed scheme requires validation on other mixture types.