Development of dynamic modulus-based mixture blending chart for asphalt mixtures with reclaimed asphalt pavement

The current practice of using the binder blending chart to select a performance grade of the virgin binder may not be applicable for mixtures containing more than 25% reclaimed asphalt pavement (RAP), since the binder blending chart assumes full blending between virgin and RAP binders. For such high RAP percentage cases, a blending chart based directly on the performance of mixtures would be a better choice. This study develops a mixture blending chart based on the dynamic modulus values of RAP mixtures to better control their performance. Three rules of mixtures were considered to develop the mixture blending chart, including Voigt rule, Reuss rule, and a joint Voigt and Reuss (V & R) rule. The dynamic modulus values of three sets of RAP mixtures were measured in this study. The results indicated that the dynamic modulus values calculated by the joint V & R rule matched the measured values of the corresponding RAP mixtures better than those calculated by the Reuss rule and Voigt rule. Digital images of two-dimensional slices of the laboratory specimens were taken and used to construct the ideal binary-blended RAP mixtures, and the finite-element analyses were conducted to determine the modulus values of these digital RAP mixtures to verify the developed mixture blending chart. The modulus results of digital RAP mixtures matched the modulus values determined based on the joint V & R rule. We conclude that the joint V & R rule could be used as the mixture blending chart to select an appropriate virgin binder when designing high RAP content mixtures.