Development of a Predictive Model for the Indirect Tensile Strength Load–Displacement Curve for Asphalt Mixtures

The indirect tensile (IDT) strength test is one of the common laboratory tests conducted to characterize asphalt mixtures. The IDT load–displacement curve is used to calculate various indicators to evaluate the cracking performance of asphalt mixtures. This study evaluated the effect of the mix composition on the IDT load–displacement curve. Asphalt mixtures with different characteristics, including binder content, binder grade, and mix gradation, were prepared and tested. The study developed statistical regression models to predict the entire IDT load–displacement curve using parameters that describe the mix composition and properties, including the binder complex shear modulus and phase angle, aggregate gradation, and binder content. The results demonstrated that the predicted model parameters were found to correlate well with those calculated from the experimental IDT load–displacement curves. All predicted cracking performance indicators calculated from the predicted IDT load–displacement curve had a strong correlation with those calculated from the measured IDT load–displacement curve. The proposed model can be used as a tool to check the preliminary cracking performance of the asphalt mixtures during the mix design stage. In addition, the mix composition can be adjusted to improve the cracking performance of the designed mix (e.g., adjust binder grade, binder content, gradation, etc.).