Experimental Study on Shear Performance of UHPC-NC Interface
Ultra-high performance concrete(UHPC)has great application prospects in engineering structure reinforcement.The reliability of the bonding properties at the interface between the new UHPC reinforcement layer and the old concrete structure is critical for ensuring the serviceability of the reinforced structures.To determine the influence of different interface treatments on the bonding properties at the interface between the UHPC and normal concrete(NC),six Z-shaped UHPC-NC bonding specimens were designed,and the bonding properties of the UHPC-NC with three different kinds of interface,namely smooth,chisel,chisel+reinforced,were investigated.In addition,nonlinear finite element models for the concrete interface were established to determine the distribution law of bonding stresses of different UHPC-NC interfaces under shear loads.The results show that the bonding properties of the UHPC-NC interface increase with the increase in the interface roughness,and interfacial shear reinforcements can postpone the debonding and cracking of the concrete interface.Compared to the smooth UHPC-NC interface,the shear strength,stiffness,and elastic stiffness of the concrete interface with an average chisel depth of 4 mm and four shear reinforcements with a diameter of 8 mm are improved by 156.1%,10.9%,and 101.0%,respectively.With the continuous development of interfacial cracks,the shear stress distribution of the UHPC-NC interface treated with chisel and reinforcement becomes more and more uniform,and the residual bonding effect of the interface is mainly provided by the interfacial shear reinforcement.
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