Bond Splitting Tensile Behavior Between Existing Concrete and High Ductility Cementitious Composite with Totally Recycled Fine Aggregate

Concrete structures are susceptible to serious aging and damage under various external loads and corrosive environments. The fiber bridging effect in high ductility cementitious composite with totally recycled fine aggregate (R-HDCC) can prevent the propagation of crack, addresses issues such as microcracks, delamination, and spalling at the repair interface, resulting in effective repair outcomes. Additionally, it promotes the recycling of waste concrete, thereby reducing environmental pollution. Reliable bonding between R-HDCC and existing concrete is essential for effective repair. The bond behavior between existing concrete and R-HDCC was investigated through the splitting tensile test considering the effects of concrete compressive strength, R-HDCC compressive strength and fiber volume fraction, and compared with that between existing concrete and high ductility cementitious composite with natural fine aggregate (N-HDCC) in this study. Acoustic emission technology was employed during the loading process to monitor damage in the bond specimens and SEM was used to observe the microstructure of bonding interface after loading. The results show that due to the higher water absorption and finer particle size of the recycled fine aggregate, the interface structure between the concrete and R-HDCC is denser. Consequently, the bond strength between the fibers and the interface matrix in concrete/R-HDCC bond specimen is higher, leading to higher peak splitting tensile stress and peak lateral deformation compared to those of concrete/N-HDCC bond specimen. The peak splitting tensile stress and lateral deformation of concrete/R-HDCC bond specimen increases with the increasing in concrete and R-HDCC compressive strength, while the fiber reinforcement on splitting tensile strength reaches its maximum when the concrete compressive strength is 56.25 MPa and R-HDCC compressive strength is 56.07 MPa. Additionally, increasing fiber volume fraction can change the failure mode from brittle to ductile and enhance the peak splitting tensile stress and lateral deformation. Finally, a bond splitting tensile stress-lateral deformation model for concrete and R-HDCC is established based on the test results, providing a valuable reference for the application of R-HDCC in structural repair.