Highly stable surfactant-crumb rubber-modified bitumen: NMR and rheological investigation

In this paper the properties of a new modified bitumen with crumb rubber (CR) additive and stabilising surfactants (a fatty acid – FA and an organosilane OS) are investigated. The characterisation of the surfactant-CR binder has been conducted by a set of laboratory tests, as penetration, softening point and Fraass breaking point, and by comparison with a reference neat bitumen and a CR modified bitumen. Dynamic shear rheometer (DSR) tests and nuclear magnetic resonance relaxometry (T2-NMR) were used to investigate the rheological properties and the molecular interactions of both pristine and modified bitumen. The stability of the bitumen systems was determined by the Tuben test method. Experimental results suggest a clear improvement of the viscoelastic properties of the modified bitumen. All data show that surfactant-CR binder features comply with standard requirements. Surfactant modification, in fact, is crucial because it allows using CR as a modifier with elimination of its separation during transportation and storage at high temperature.