Characterisation of crumb rubber modifier using solid-state nuclear magnetic resonance spectroscopy

Crumb rubber (CR) can be used for binder modification or aggregate replacement in asphalt mixtures for road construction, when it is usually referred to as CR modifier (CRM). CRM elastic properties depend on the quality of parent material and storage conditions of final material. They deteriorate in time due to degradation processes and among other things they can influence CRM swelling capacity during asphalt rubber preparation. The presented paper demonstrates the sensitivity of basic nuclear magnetic resonance (NMR) parameters (proton spin-lattice relaxation time T-1, proton spin-spin relaxation time T-2 and the line broadening in C-13 NMR and H-1 NMR spectra) for detecting changes in CRM degradation. These NMR parameters are proposed to be used to assess CRM degradation before application in asphalt mixtures. In laboratory conditions, CRMs with different degrees of degradation were prepared by thermal ageing at 85 degrees C for 0-36 days.