Viscoelastic mechanical performance of dense polyurethane mixtures based on dynamic and static modulus testing and creep testing

Abstract

Asphalt mixtures are pavement materials that are susceptible to permanent deformation due to the weakening of asphalt at high temperatures. Aimed at finding a new binder with less temperature sensitivity, this paper presents two types of dense polyurethane mixtures, Stone Matrix polyurethane (SMPU-13) and Superpave polyurethane mix (SUPU-20), in which the polyurethane binder was used to replace asphalt binder. The dynamic modulus, phase angle, static modulus, and creep properties of the two polyurethane mixtures and Stone Matrix Asphalt (SMA-13) were compared to display whether the polyurethane mixtures possess better viscoelasticity. It is found that the residual dynamic moduli of the polyurethane mixtures are greater than 8000 MPa and their phase angles are not higher than 6° at 60 °C, while the dynamic modulus of SMA-13 has declined to 189 MPa at 50 °C with its phase angle being about 30°. The dynamic modulus test results show that the two dense polyurethane mixtures are viscoelastic materials dominated by elastic characteristics within the normal working temperature and loading frequency of the pavement, and their mechanical properties are more stable than those of the asphalt mixture. There is a linear correlation between the dynamic modulus and the static modulus of the polyurethane mixtures when the temperature is higher than 20 °C. And the two moduli can be transformed into each other through an established formula. The creep curves of the two polyurethane mixtures exhibit only the first two stages of creep deformation, with the third stage not appearing within a comparatively long loading time, indicating better resistance to permanent deformation.