Experimental study on bond performance of UHPC-to-NC interfaces: Constitutive model and size effect

• Published in: Engineering structures Vol. 317; p. 118681
• Main Authors: He, Shaohua, Huang, Xu, Zhong, Huaqian, Wan, Zhiyong, Liu, Gao, Xin, Haohui, Zhang, Youyou
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 15.10.2024
• Subjects: Bond interface property; Constitutive model; Size effect; UHPC-NC; Weibull theory; UHPC-NC; Constitutive model; Weibull theory; Bond interface property; Size effect
• ISSN: 0141-0296
• DOI: 10.1016/j.engstruct.2024.118681

This study investigates the constitutive model of the adhesive bond between normal concrete (NC) and ultra-high-performance concrete (UHPC), focusing on the impact of varying bond dimensions. Two distinct series of UHPC-NC bonding specimens were prepared and tested, comprising eight direct-shear and fifty-six pull-off specimens. The experimental results were presented and thoroughly discussed, including failure modes, bond stress, load-displacement curves, and strain histories of the UHPC-NC interfaces. The findings indicate that an average surface roughness of 4 mm on NC substrates guarantees adequate shearing and tensile bonding strength with UHPC, adhering to the standards outlined in ACI 546.3R-14. An increment in the bond length, ranging from 100 mm to 440 mm, reduced interfacial shear stiffness by 50.8 % while enhancing the shear strength by 14.4 %. Conversely, an enlargement in the core diameter, from 50 mm to 100 mm, decreased the tensile bond strength at the interface by 18.1 %. Furthermore, theoretical models were formulated to predict the bonding properties across the UHPC-NC interface, utilizing the size effect law and Weibull theory principles. The accuracy of these models was confirmed through a validation process using both current experimental data and external sources. The comprehensive findings of this study provide a valuable reference for optimizing the application of UHPC in concrete bridge restoration projects. •Bond performance of UHPC-NC interface under shear and tension loads is experimentally evaluated.•Constitutive model of the NC-UHPC interface bond is analyzed.•Influence of size effect on the UHPC-NC interface bond is determined.•Analytical model to calculate the UHPC-NC interface bond is derived.