Investigation of bitumen low temperature properties using a dynamic shear rheometer with 4 mm parallel plates

This paper investigates the low temperature rheological properties of bitumen using a dynamic shear rheometer with 4 mm parallel plates (4-mm DSR). Different procedures of sample preparation were tested and evaluated. For comparison, low temperature measurements were also carried out using a bending beam rheometer (BBR). Test results show that the 4-mm DSR can perform rheological measurements at very low temperatures (down below −30 °C). With this geometry, very little amount of bitumen sample is required. There are certain statistical correlations between complex modulus measured by 4-mm DSR and creep stiffness by BBR, and also between phase angle and m-value. With the BBR data at 60 s loading time, higher correlation coefficients were observed at lower DSR frequencies or at a frequency corresponding to the 60 s loading time. For the limiting temperatures, a statistical correlation was found in LST between the two test methods; however, there was very weak or no correlation in LmT. The presence of waxes in bitumen seems to have a negative effect on the correlations between the 4-mm DSR and BBR. This is probably due to differences in thermal histories caused by the large differences in sample size between BBR and DSR tests. In addition, DSR with 8-mm plates can be applied to certain low temperatures, depending on instrument compliance and stiffness of the binder to be tested.