Estimating the Unrecovered Strain During a Creep Recovery Test from the Material's Volumetric-flow Rate

The ineffectiveness of the Superpave specification parameter | G * |/sin i , in capturing the high temperature performance of paving asphalts, especially some polymer-modified ones, has led researchers to seek other possible parameters that may relate to rutting resistance better. Some researchers suggested a repeated creep and recovery test as a means to obtain a new rutting parameter, while other researchers suggested a refinement to the existing Superpave specification parameter. A new parameter defined as | G * |/(1 mm (1/tan i sin i )) was previously derived from basic principles and proposed as a refined Superpave specification parameter for future use. This new parameter was shown to essentially give the same information as that obtained through a repeated creep and recovery test. The present work demonstrates a simpler method to obtain the unrecovered strain during a repeated creep and recovery test and uses the material's volumetric-flow rate (MVR) to get this information. While the repeated creep and recovery test as well as the | G * |/(1 m (1/tan i sin i )) parameter are obtained from the Dynamic Shear Rheometer, the MVR is obtained from a simple Flow Measurement Device (FMD). The FMD is a relatively inexpensive portable piece of equipment with low operational costs, and, through minimal training, the MVR data can be generated with a low level of variability. Thus, the proposed method of estimating the unrecovered strain during a repeated creep and recovery test from the MVR is greatly advantageous.