Practical Procedure for Developing Dynamic Modulus Master Curves for Pavement Structural Design (05-0389)**
Ramon Bonaquist, Advanced Asphalt Technologies, LLC
Donald Walter Christensen, Advanced Asphalt Technologies, LLC

A dynamic modulus master curve for asphalt concrete is a critical input for flexible pavement design in the Mechanistic-Empirical Pavement Design Guide developed in National Cooperative Highway Research Program (NCHRP) Project 1-37A. The recommended testing to develop the modulus master curve is presented in AASHTO Provisional Standard TP 62-03ˇ§Standard Method of Test for Determining Dynamic Modulus of Hot-Mix Asphalt Concrete Mixtures.ˇ¨ It includes testing at least two replicate specimens at five temperatures between 14 and 130 „aF (-10 and 54.4 „aC) and six loading rates between 0.1 and 25 Hz. The master curve and shift factors are then developed from this database of 60 measured moduli using numerical optimization. This testing requires substantial effort, and the data collected at extremely high and low temperatures are highly variable. Additionally, there is much overlap in the measured data, which is not needed when numerical methods are used to perform the time-temperature shifting for the master curve. This paper presents an alternative to the testing sequence specified in AASHTO TP62-03. It requires testing at only three temperatures between 4 and 115 „aF (4 and 46.6 „aC) and four rates of loading between 0.01 and 10 Hz. An analysis of data collected using the two approaches shows that comparable master curves are obtained. This alternative testing sequence can be used in conjunction with the Simple Performance Test System developed in NCHRP Project 9-29 to develop master curves for structural design.