Obtaining asphalt binder rheological properties from BBR strength test—the effect of loading rate

Abstract

Selecting asphalt binders that have good cracking resistance at low temperatures is the first step in designing asphalt mixtures for durable asphalt pavements in cold regions. To evaluate low-temperature cracking resistance of binders, rheological properties (creep stiffness and m-value), and fracture properties (failure stress and strain) are required. Recently, a new strength test was developed to measure the fracture properties of binders using a modified BBR (Bending Beam Rheometer), called BBR-Pro. In this paper, we investigate the idea of using the BBR strength test to also obtain rheological properties. We performed strength tests at different loading rates and verified the assumption of linear viscoelasticity (LVE) condition of binders at these loading rates. We used analytical and numerical methods to obtain creep compliance from strength test experimental data and compared the results to experimental creep compliance data. We have found that both methods predict creep compliance and creep stiffness values similar to the experimental results, whereas the numerical method is more accurate than the analytical method for obtaining the $m$ -value. We also found that the BBR strength test performed using the original loading rate is too short to accurately predict rheological properties for 240 s. We show that by reducing the loading rate we achieve good estimation of creep compliance.