A Re-Look at the Asphalt Mixture Performance Test Protocols and Computational Algorithms

Asphalt mixture performance tests (AMPTs) are developed to complement the Superpave volumetric mix design procedure and to reliably measure the mechanical response characteristics of the asphalt mixtures. The AMPT protocols, such as dynamic modulus, flow time and flow number test protocols, and the computational algorithms for post-processing of data are in the development stages and require further refinement. In this investigation, AMPTs were carried out on asphalt mixtures with unmodified, polymer-modified, and crumb-rubber-modified binders. Dynamic modulus test was carried out for a wide range of temperatures and frequencies and master curves were constructed. It was observed that the American Association of State Highway and Transportation Officials (AASHTO) procedure for master curves does not take into account the influence of phase angle, and this could hinder the effective use of this input in pavement design and analysis. Flow time and flow number tests were carried out for an extended time of 100 000s (cycles) rather than the currently practised 10 000s (cycles) protocol. The test data was used in assessing the various algorithms for evaluating flow values. A wheel tracking test was also carried out and it was found that the response of mixtures could be correlated to wheel tracking test results in a qualitative manner to the flow time test.