Interlaboratory study on low-temperature testing of asphalt binders using the dynamic shear rheometer in Germany

In 2023, a comprehensive interlaboratory study was conducted to analyse low-temperature asphalt binder characterisation in the dynamic shear rheometer (DSR). Participants from 17 German laboratories with 20 DSR devices from two manufacturers tested three representative asphalt binders (70/100, 10/40–65 and 40/100–165). The study included two approaches: temperature-frequency sweeps with 4 mm parallel-plate geometry from −30°C to 0°C and shear relaxation tests with 8 mm plates at −10°C. Key parameters such as the complex shear modulus (G*), the phase angle (δ), the relaxation viscosity (λREL) and the relaxation capacity (RELSRV) were extracted and statistically analysed in accordance with ISO 5725-2 standard. The results showed good repeatability within laboratories, regardless of instrument type. However, interlaboratory reproducibility was limited, primarily due to operator-related variability and calibration practices. Despite these challenges, both test protocols enabled consistent differentiation of asphalt binders and offer material-efficient, DSR-based alternatives to BBR testing.