Development of a performance based binder specification for rutting using creep and recovery testing
Date
2009
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Abstract
The inadequacy of the Superpave high temperature specification parameter, G*/sin 8, to correctly grade the superior field performance of modified asphalt binders has been demonstrated by several researchers. A new parameter that is blind to modification type and is performance based is now needed. As a replacement for the existing high temperature binder parameter (G*/sin 8), this study has developed an easy to use Multiple Stress Creep and Recovery Test (MSCR) that measures fundamental characteristics of asphalt binders. In this study, several binder parameters proposed to replace the existing Superpave rutting parameter were validated using hot-mix testing. Several different binder tests were evaluated to determine which would provide a replacement for the Superpave high temperature binder criteria. The new test and criteria will have to be performance related and blind to modification. The results from these binder tests were compared against hotmix rutting results from the Asphalt Pavement Analyzer, the Hamburg Wheel Tracking Test, the FHWA ALF test sections and field roadway sites. The results from the hot-mix rut testing showed that different rut testers will provide completely different ranking of binders. This difference is related to the stress level applied by the different testers. This hot-mix testing indicates that the different binders, specifically the polymer modified binders, have different stress dependencies. A separate sub-study was also conducted in this research to understand the effect of stress and strain on the microstructure of polymer modified binders. It was found that in MSCR data there is a clear relationship between percent recovery in the recovery portion of the test and percent strain in the creep portion of the test. Very high creep strain causes yield behavior in polymer modified asphalt binders (PMA). After the high creep strain, PMA's still exhibit recovery but the rate of recovery is reduced. At high strain, binder morphology, tensile and shear properties change. A test procedure was developed to run creep and recovery testing on one sample at multiple stress levels (MSCR). This test procedure makes it easy to evaluate how the binder response will change under different stress conditions. A property called nonrecoverable compliance lnr was developed based on the non-recovered strain at the end of the recovery portion of the test divided by the initial stress applied during the creep portion of the test. The Inr value normalizes the strain response of the binder to stress which clearly shows the differences between different polymer-modified binders.
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Bibliography: p. 135-142
Some pages are in colour
Some pages are in colour
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Citation
D'Angelo, J. (2009). Development of a performance based binder specification for rutting using creep and recovery testing (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca. doi:10.11575/PRISM/2384