Investigation of the rheological properties and storage stability of CR/SBS modified asphalt

• CR/SBS modified asphalt shows increased viscoelastic moduli and viscosity.
• Moderate asphaltenes and high aromatics are necessary for this modification.
• CR/SBS modified asphalt appears obvious phase separation at the storing period.
• CR could be an alternative for reducing SBS from view of economic and environment.

The rheological properties and storage stability of CR/SBS modified asphalt have been investigated in this study. Crumb rubber (CR) as well as SBS was blended with asphalt having different chemical composition to prepare CR/SBS modified asphalt by high-shear mixer. Linear viscoelastic and viscous measurements, fluorescence microscopy as well as storage stability tests were performed on unmodified and CR/SBS modified asphalt. The results revealed that the addition of CR/SBS to asphalt produces a remarkable improvement in viscoelastic characteristics and viscosity compared with neat asphalt. Consequently, an enhanced resistance to permanent deformation is expected in road. Crumb rubber replacing parts of SBS to produce CR/SBS modified asphalt is feasible because failure temperature, moduli and viscosity undergo a significantly increase when the dosage of SBS exceeds 1%. The chemical composition of base asphalt for this special modification is crucial. In other words, moderate asphaltenes and high aromatics are suggested in order to achieve desired rheological properties. CR/SBS modified asphalt appears obvious phase separation at the storing period resulting from coalescence of SBS particle at the top of sample and sedimentation of rubber particles at the bottom. Thus, CR/SBS modified asphalt must be used swiftly after which has been produced owing to its poor storage stability. Anyhow, crumb rubber could be an alternative for reducing use of virgin SBS from economic and environmental point of view.

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