Various parameters have been proposed to refine the current Superpave high-temperature binder specification. One parameter relates the phase angle (delta) directly to accumulated strain from the creep-recovery test. Another variation suggests a formula to predict the accumulated strain using the current Superpave parameters G* and sin delta. Recently, NCHRP 9-10 project suggested a criterion based on a parameter derived from Burger's viscoelastic model. In Europe, zero-shear viscosity is being proposed as a high-temperature specification parameter. These and other criteria proposed for high-temperature specification are evaluated by examining the correlation of each criterion to pavement performance. The experimental design consists of five asphalt binders used in the Federal Highway Administration's accelerated loading facility. Additionally, two binders used by the Nevada Department of Transportation in construction of I-80 test sections were tested. Results show that the zero-shear viscosity correlates reasonably well with performance and is the best parameter among those evaluated. However, accurate determination of the zero-shear viscosity is time-consuming and requires expensive instrumentation, which makes it unsuitable as a specification parameter. Therefore, an easy method of obtaining zero-shear viscosity was evaluated and found to correlate to performance equally well. In this method, data from a single frequency sweep at the specification temperature are used to estimate the zero-shear viscosity. This method can be implemented immediately with little or no training or need for new instrumentation.
Abstract