Application of time-temperature superposition principle for cracking characterization of asphalt mixtures using semi-circular bend test

Abstract

In recent decades, numerous laboratory tests have been developed to characterize the cracking performance of asphalt mixtures. Among these, the semi-circular bend (SCB)-based Illinois flexibility index test (I-FIT) (AASHTO T 393) has emerged as a favored method due to its straightforward specimen preparation and better sensitivity to mixture variables. However, the cracking susceptibility of asphalt mixtures is significantly influenced by temperature and loading rate, leading to a discrepancy in performance between standard test conditions and real-world scenarios. To address this challenge, this study explores the applicability of the time-temperature superposition principle (TTSP) for the SCB test. The study evaluates four mixtures incorporating reclaimed asphalt pavement (RAP) and/or reclaimed asphalt shingles (RAS) across various loading rates and temperature combinations. Findings suggest that TTSP can be applied to the SCB test without significantly impacting cracking performance indices such as flexibility index and post-peak slope. Furthermore, the study also demonstrates that TTSP can be applied in the crack propagation phase during the post-peak domain of the mixtures. The findings of the study will allow laboratories to develop more flexible testing plans without compromising the accuracy and reliability of performance parameters by adjusting the loading rate corresponding to the test temperature and vice versa. Consequently, this approach can potentially make a balanced mix design (BMD) practice more implementable.