AbstractThe State of Vermont began implementing balanced mix design (BMD) in late 2019. Since 2020, both Hamburg wheel tracking test (HWTT) and Illinois flexibility index test (I-FIT) results were required to be included in the mix design submittal along with the traditional Superpave volumetric design. This paper presents a part of the ongoing benchmarking efforts in Vermont, among many other states around the country, and compares the sensitivity of the two popular intermediate temperature cracking tests [I-FIT and indirect tensile cracking test (IDEAL-CT)] to the design factors of mixes produced in Vermont. Both laboratory-produced and plant-produced mix data are evaluated, and the factors analyzed include mix type, design gyrations, production facility, binder grade, and binder supplier. We found that IDEAL-CT shows much higher sensitivity to the design factors than I-FIT according to the data presented in this study. Therefore, it is recommended that Vermont Agency of Transportation (VTrans) adopt IDEAL-CT as the intermediate temperature cracking test for BMD implementation rather than I-FIT, due to the higher sensitivity and simplicity of IDEAL-CT. Regression models are further developed for IDEAL-CT using selected mix properties to guide the mix design adjustment. Similar studies are highly recommended for other state agencies that are interested in implementing BMD.

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