Development of a Flow Number Predictive Model

Abstract

The NCHRP 9-19 panel recommended the repeated load permanent deformation test as a laboratory procedure that could be used to evaluate the resistance of a hot-mix asphalt (HMA) to tertiary flow. No standard test protocol addresses the required laboratory stress to be applied. The test can take several hours until tertiary flow is reached and in many cases the sample may never fail. A model capable of predicting or providing general guidance on the flow number characteristics of a mix can be of great value. The model can be ideally used as a guideline to determine the stress–temperature combination that will yield tertiary flow within a reasonable testing time. In this study, an effort was undertaken to develop a flow number predictive model. The model uses HMA mixture volumetric properties and stress–temperature testing conditions as predictor variables. The laboratory test data used are a combination of two valuable databases. The first one included tests conducted at Arizona State University; the second one included tests conducted by the FHWA Mobile Asphalt Material Testing Laboratory. Ninety-four mixtures were evaluated, and 1,759 flow number test results were available. Various regression models were evaluated by combining several independent variables. The final model selected had fair statistical measures of accuracy, and it covered a wide range of mixtures, gradations, and binder properties, as well as laboratory-applied stress. As more testing data become available, the model could be refined and recalibrated for better accuracy.

Improving Recycled Asphalt Mix Performance Through Rejuvenation

“…The results of flow number tests from five mixes are shown in Figure 5, which indicates the flow point of each mix (17). Notable differences in flow behavior are found among the mixes.…”

Using Mixture Design Data and Existing Prediction Models to Evaluate the Potential Performance of Asphalt Pavements

“…In 2010, Rodezno (46) further modified this model based on a larger database, to tailor the changes in the environment selected. The finalized model, that is also going to be used in this study is the following: For the purpose of this study, the loading frequency is taken to be equivalent to 18 Hz.…”

“…In 2010, Rodezno (46) developed a predictive Flow Number model. A large database was generated and put together in order to make the model as comprehensive as possible, under different stress levels, temperature combinations, gradations and binder types.…”

Sensitivity of the Flow Number to Mix Factors of Hot-Mix Asphalt

“…The effects of different mix factors on the flow number have also been studied by different researchers [3][4][5][6]. Kaloush [3] determined that the flow number increases with the viscosity of binder and decreases with the test temperature, effective binder content, and air voids.…”

“…Christensen [5] applied various statistical techniques to relate the flow number with the applied stress level and observed that the flow number decreases with increasing applied deviator stress. Rodezno et al [6] determined that the flow number increases with the viscosity of the binder; however, it decreases with the test temperature and air voids and is affected by aggregate gradation. The current study was not intended to investigate the viscosity of the binder or the test temperature.…”