Research on Crack Propagation Behavior of UHPC-NC Interface Under Stress Wave

For the ultra-high performance concrete (UHPC) overlaying normal concrete (NC) structures, the reliable interface performance between UHPC and NC is the foundation for achieving their good co-work behavior. The paper focused on the experimental and theoretical research on the crack propagation at the interface of these UHPC-NC configurations under stress waves. A bi-material notched semi-circle bent (BNSCB) configuration was proposed, and the impact tests were conducted on the BNSCB specimens using a split Hopkinson pressure bar system (SHPB), examining the differences in the interfacial impact performance between UHPC with different strengths and NC. Based on the finite element method and crack propagation gauge, the complex stress intensity factor (CSIF) at the crack tip of the interface of BNSCB specimen was calculated. The results showed that: 1) under stress wave action, interface cracks in the BNSCB specimens tended to propagate along the aggregate-cement matrix interface; 2) the maximum velocity of interface crack propagation in the BNSCB specimen did not exceed the Rayleigh wave velocity of UHPC; 3) the parameter <italic>K</italic>₂ at the crack tip of the BNSCB specimen was much smaller than <italic>K</italic>₁, and the parameter <italic>K</italic>₁ played a dominant role in crack initiation; 4) there was no obvious relations between the parameter <italic>K</italic>₂ in CSIF and UHPC strength grades.