NSM – Technique with geopolymer adhesive to strengthened the RC beams in shear

• Main Authors: Salman, Wissam D., Abdullah, Mohamed A.
• Format: Conference Proceeding
• Language: English
• Subjects: Adhesive bonding; Bonding strength; Epoxy adhesives; Errors; Failure modes; Geopolymers; Grooves; High temperature; Mechanical properties; Reinforced concrete; Reinforcing steels; Shear; Strengthening; Ultimate loads
• ISSN: 0094-243X; 1551-7616
• DOI: 10.1063/5.0236396

This study offered an experimental program on the strengthening of RC beams in shear by near-surface mounted technique steel bars with geopolymer adhesive. Strengthened RC beams are required due to various reasons such as updating codes, increased serving loads, design errors, and errors during construction. Various techniques are provided for strengthening RC beams in shear but the Near Surface Mounted (NSM) technique is considered the most effective technique. In the NSM technique groove is formed on the outside cover of the concrete member, half of the groove is filled by adhesive, then the steel bar is mounted into the groove, and after that the groove with adhesive. Always, epoxy adhesive was used in the NSM technique when strengthening the RC beams in shear but due to losses in its mechanical properties at high temperatures, we replaced it with another adhesive. In this study in addition to epoxy adhesive, we used geopolymer adhesive to strengthen the RC beams in shear which is considered the first study on using geopolymer as an adhesive material in strengthening RC beams in shear by NSM technique. The experimental program included casting and testing seven RC beams with dimensions (150mm*250mm*1200mm) without stirrups. The variables include the type of adhesive material (epoxy or geopolymer), and spacing of NSM – bar (50,100, and 160mm). One of the RC beams was used as a control beam (unstrengthened) and the NSM technique was used to strengthen other beams with the above variables. The test results included the ultimate load, deflection, cracking loads, strains at bars and concrete, and failure mode. The outcomes of this study display that the geopolymer adhesive provided excellent bond strength due to an increase in the ultimate load and first crack load of strengthened beams up to 89% and 37%, respectively over than control beam, thus it can be used as adhesive material with NSM technique when strengthened the RC beams in shear, using NSM – steel bars in shear strengthened of RC beams improved the ultimate load capacity and first crack load of strengthened beams up to (118 and 37%), respectively over than control beam, and one of the strengthened beams were converted from shear failure to flexural failure.