*Article* **Experimental Research on Interfacial Bonding Strength between Vertical Cast-In-Situ Joint and Precast Concrete Walls**

**Changyong Li, Yabin Yang, Jiuzhou Su, Huidi Meng, Liyun Pan \* and Shunbo Zhao \***

International Joint Research Laboratory for Eco-Building Materials and Engineering of Henan, School of Civil Engineering and Communications, North China University of Water Resources and Electric Power, Zhengzhou 450045, China; lichang@ncwu.edu.cn (C.L.); yangyabin@ncwu.edu.cn (Y.Y.); z201710313228@stu.ncwu.edu.cn (J.S.); Z201910311259@stu.ncwu.edu.cn (H.M.)

**\*** Correspondence: ply67@ncwu.edu.cn (L.P.); sbzhao@ncwu.edu.cn (S.Z.); Tel.: +86-371-65665160 (S.Z.)

**Abstract:** In the monolithic precast concrete shear-wall structure, the bonding property of cast-in-situ joints to precast concrete walls is important to ensure the entire structural performance. Aiming to the vertical joint of precast concrete walls, an experimental study was carried out considering the factors including the strength of precast and joint concretes, as well as the interface processing and casting age of precast concrete. The micro-expansion self-compacting concrete was used for the cast-in-situ joints. The interfacial bonding strength between joint and precast concrete was measured by splitting tensile test. Results show that the interfacial bonding strength was benefited from the increasing strength of joint concrete and the spraying binder paste on the interface of precast concrete, and unbenefited from the overtime storage of precast concrete. The washed rough surface with exposed aggregates improved the interfacial bonding strength, which increased with the increasing roughness. Based on the test results, the limits of the strength grade of joint concrete and the roughness of washed rough surface are proposed to get the interfacial bonding strength equivalent to the tensile strength of precast concrete. Meanwhile, the spraying of binder paste on precast concrete is a good choice, the storage time of precast components is a better limit within 28 days.

**Keywords:** precast concrete wall; interfacial bonding strength; joint concrete; interface processing; washed rough surface; roughness; storage time
