Experimental evaluation of concrete-to-UHPC bond strength with correlation to surface roughness for repair application

• Published in: Construction & building materials 2020-03, Vol.238, p.117753, Article 117753
• Main Authors: Valikhani, Alireza, Jahromi, Azadeh Jaberi, Mantawy, Islam M., Azizinamini, Atorod
• Format: Article
• Language: English
• Subjects: Bond strength; Concrete; Digital image processing; Interface; Repair; Terrestrial laser scanning; Ultra-high performance concrete
• ISSN: 0950-0618; 1879-0526
• DOI: 10.1016/j.conbuildmat.2019.117753

•The bond strength between UHPC and concrete substrate was investigated experimentally.•30 specimens were tested using bi-surface shear test and different surface preparation.•Sandblasting is necessary to achieve better bond strength between UHPC and NC.•Two non-contact methods were incorporated to evaluate concrete surface roughness.•The substrate roughness degree is correlated to bond strength between UHPC and NC. Exposing bridge elements to severe environmental conditions causes a reduction in service life and durability which demands repair or total replacement. Different strategies for repair and retrofit can be chosen. These strategies include patching, crack repairs, concrete sealers, a protective layer made of concrete or steel. Ultra-high performance concrete offers an option for repairing and retrofitting different structural elements, however, the bond strength between concrete substrates and ultra-high performance concrete can still be considered a knowledge gap in the literature. In this paper, bond strength between ultra-high performance concrete and substrate made of normal concrete with different surface preparation was investigated experimentally. Thirty specimens were tested under bi-surface shear test with different surface preparation, including roughness degree, mechanical connector, and bonding agent. Furthermore, two non-contact test methods including terrestrial laser scanning and digital image processing were incorporated to evaluate the roughness of the substrate interface and correlate the roughness degree to the bond strength between the two materials. The results showed that an adequate roughness for the interfacial surface with or without mechanical connectors transferred the failure mode to the concrete substrate indicating high bond strength between the two materials if compared to interfacial surfaces without any preparat;ion. In addition, the use of bonding agent could harm the bond strength between the two material which is inappropriate for retrofitting. The result from scanning and image processing showed that both methods qualitatively identified the degree of interface roughness and their result can be correlated to bond strength.