Advances in the Rheology of Synthetic Binder for Sustainable Road Pavements: An Improved Protocol for DSR Testing

Bituminous binders are thermal-dependent visco-elastic materials commonly used in pavement engineering. However, synthetic binders represent quite a new family of products that can be used in the substitution of conventional binders with various purposes. Among them, clear synthetic resins recently experienced a quick diffusion since they can be employed in the production of sustainable road pavements (which address aesthetic concerns, thermal aspects, etc.). Since specific studies addressing the rheological modeling of clear synthetic binders cannot be found in the literature, the purpose of this research is setting up an advanced rheological protocol to characterize such materials, bridging the existing knowledge gap. An extensive laboratory investigation with the dynamic shear rheometer was carried out in oscillatory mode (amplitude and frequency sweeps) to analyze the stress–strain state of such binders. An innovative test at a constant strain rate was used to construct non-linear master curves, overcoming various criticisms about the stress state of the binder when subjected to time-dependent deformations. Results indicated that, using non-linear data, horizontal and vertical shift factors (functions of temperature and strain rate) can be modeled through power law equations to obtain the master curves. This method was considered suitable for depicting the rheological response of the binders displaying such complex behaviors.