Modified cement-based adhesive for near-surface mounted CFRP strengthening system

The strengthening system with near-surface mounted (NSM) has emerged in last decades as a promising technology to improve the flexural and shear strength of concrete structures. Large number of concrete structures have been strengthened worldwide by this technique using epoxy adhesives. However, the rapid deterioration of the mechanical properties of epoxy-based polymer matrix at elevated temperature, and the hazardous effects of toxic fumes during the application made the need of replacing this polymer with a new cementitious bonding agent to enhance the performance of concrete structures in high-temperature environments and reduce the environmental and health hazards. The application of cement-based adhesive has been studied for externally-bonded techniques using CFRP textile. Although, the good bond properties has been achieved, debonding was the critical failure between fibre and concrete substrate. To exploit the advantages of NSM technique, a new modification of cement-based adhesive has been achieved to be compatible with requirements of NSM application system. To assess the efficiency of this adhesive, an experimental investigation of pull-out testing using a single-lap shear test set-up was conducted to study the bond characteristics between CFRP textile and concrete. Four different mixes were used in this investigation. The test results show the efficiency of the NSM technique using modified cement adhesive and its superior bond properties compared to externally-bonded CFRP.