Evaluation of Fatigue Damage and Healing Capability of RAP Mixtures Using Time Lag: An ITSM Test Parameter

Mullapudi, Ramya Sri and Chowdhury, Priyadarshini Saha and Kusam, Sudhakar Reddy (2022) Evaluation of Fatigue Damage and Healing Capability of RAP Mixtures Using Time Lag: An ITSM Test Parameter. International Journal of Pavement Research and Technology. ISSN 1996-6814

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Abstract

Time lag, extracted from the results of the indirect tensile stiffness modulus (ITSM) test, which is a routine test conducted by many organizations to evaluate the stiffness value of asphalt mixes, has been demonstrated in the past to represent the visco-elastic nature of asphalt mixes. It is also widely known that phase angle influences the energy dissipation and the visco-elastic nature of binders and mixes and consequently the fatigue damage and healing. Time lag has been used as a surrogate measure of phase angle in this investigation to correlate with fatigue life and healing indices of Reclaimed Asphalt Pavement (RAP) mixes. While the healing behaviour of conventional asphalt mixes (without RAP) has been studied extensively in the past, fatigue healing characteristics of RAP mixes is less investigated. Time lag values were obtained from the results of ITSM test conducted at test temperatures of 15, 25, and 35 °C on asphalt mixes containing different proportions (0, 15, 25, 35, and 45%) of RAP material. Indirect tensile fatigue test (ITFT) was conducted on the RAP mixtures at 25 °C. The binder blends were evaluated by conducting a linear amplitude sweep (LAS) fatigue test, Fourier Transform Infrared (FTIR) Spectroscopy, measurement of total surface free energy (SFE) using a goniometer, viscosity at 60 °C and phase angle at 25 °C. Strong correlation was observed between (a) time lag and fatigue life values of RAP mixes and (b) time lag and the healing potential of mixes. Good to fair correlations were also noted between different rheological parameters (viscosity and phase angle), chemical indices (ICO, ISO, ICC, and ICH) obtained from FTIR and SFE of the binders. The results from this investigation can be used to estimate the relative fatigue performance and healing characteristics of different asphalt mixes. © 2022, The Author(s), under exclusive licence to Chinese Society of Pavement Engineering.

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