The role of stress sensitivity of modified binders with the same linear viscoelastic properties in evaluating rutting resistance of asphalt mixtures

ABSTRACT

In the present study, stress sensitivity of modified binders in the multiple stress creep and recovery (MSCR) test and its relationship with rutting resistance of the asphalt mixtures are investigated. For this purpose, different groups of styrene butadiene styrene (SBS), polyphosphoric acid (PPA) and SBS + PPA modified binders were produced; in each of which, the binders have the same continuous high temperature performance gradings (PGs) and linear viscoelastic (LVE) properties. The MSCR tests were performed at 40°C, 55°C, and at the PG temperatures of the modified binders to consider a wide range of high pavement temperatures. To depict the stress sensitivity, stress levels of 12.8, 25.6, and 40 kPa were added to the MSCR standard procedure and the non-recoverable compliance (J_nr) and percent recovery (R) parameters were obtained at all the stress levels applied. To study the rutting resistance of asphalt mixtures prepared with the same asphalt binders, the flow number (FN) and |E*| parameters were determined at 40°C and 55°C, through the dynamic creep and dynamic modulus performance tests, respectively. Results of the MSCR test show that at the temperature range considered, the standard stresses are not sufficient to enter the modified binders into nonlinear region, thus higher stress levels should be applied to assess the nonlinearity and address the true rutting potential. Results of the mixtures performance tests show great correlations with the results of the MSCR of the modified binders at the nonlinear stress levels, especially with the J_nr parameter, regardless of the test temperatures.

KEYWORDS:

• Stress sensitivity
• modified binders
• same linear viscoelastic properties
• rutting resistance
• asphalt mixtures

Acknowledgements

The authors would like to express their sincere appreciation to Dr. Manouchehr Latifi Namin, the supervisor of the pavement laboratory of School of Civil Engineering at the University of Tehran. Moreover, the authors express their gratitude to Mr. Mohammad Rahi, the manager of the R&D centre of the Pasargad Oil Company, for his support and constructive suggestions. The authors also thank Mr. Changiz Arfaee, Mr. Aliasghar Akbari Nasrekani and Mr. Mostafa Nakhaei for their expert assistances in the tests.

Disclosure statement

No potential conflict of interest was reported by the author(s).