Performance assessment of composite modified bitumen integrated with desulfurized crumb rubber and SBS modifier as waterproofing adhesive layer

Performance of the waterproofing adhesive layer played a critical role for governing duration of bridge deck paving system due to harsh service conditions. To develop a new type of modified bitumen suitable for the layer between bridge deck and overlaid asphalt, this study investigated the performance of composite modified bitumen (CMB) integrated with desulfurized crumb rubber (DCR) and SBS modifier. The influence of DCR and SBS additive on rheological behavior, high-temperature performance, low-temperature cracking resistance, and adhesive performance of CMB was investigated by adopting various experimental tests, which including penetration, ductility, softening point, Brookfield viscosity, dynamic shear rheometer (DSR), bending beam rheometer (BBR), and bonding strength. The high-temperature stiffness and low-temperature flexibility of CMB was improved after composite modification, which in turn contributed to the shear and cracking resistance. The black diagram indicated that the formation of polymer network in the CMB improved the viscous flow resistance and maintained elastic response at high in-service temperature. The bonding strength and moisture stability of the composite bitumen-concrete interface were enhanced, with the properties exceeded the commercial SBS modified bitumen. The CMB binders R18S2 and R18S3 presented good performance and can be used for waterproofing adhesive layer as a substitute of the commercial SBS modified bitumen.