Advances in bonding agents for retrofitting concrete structures with fibre reinforced polymer materials: A review

Retrofitting, strengthening, and repairing of deteriorated concrete structures have adopted epoxy adhesives for decades to bond fibre reinforced polymer (FRP) materials to the substrate of the deteriorated concrete elements. Despite being the most commercially used solutions, epoxy adhesives show several disadvantages, in terms of the performance of the strengthened elements and the toxicity of the material. Cement-based adhesives (CBAs) have been also considered for retrofitting concrete elements, but their use is very limited due to their poor perfor-mance, for instance, their low mechanical properties (i.e. compressive and tensile strength) compared to epoxy adhesives. The nanomaterial-modified epoxy adhesives and nanomaterial-modified CBAs (i.e. innovative high-strength self-compacting cement adhesives (IHSSC-CA)) have been effective substitutes with their extraordi-nary mechanical and thermal properties. This paper overviews the development of adhesives for FRP-strengthened concrete elements, in particular of epoxy and CBAs with the addition of nanoparticles. Both the mechanical and thermal properties of strengthening FRP and bonding interfaces with various adhesives are firstly investigated and compiled, and then the performance of retrofitted/strengthened-concrete elements with the FRP composites using neat and nanoparticles-modified adhesives is studied to examine the effectiveness of the modified adhesives over neat adhesives for retrofitting. Based on the compiled developments, further de-velopments are identified, and recommendations are made for future research and innovations in this subject area.

Automated summary

This paper provides an overview of the development of adhesives for FRP-strengthened concrete elements, focusing on the use of nanoparticles to modify the performance of epoxy and CBAs. The effectiveness of the modified adhesives for retrofitting is examined by studying the mechanical and thermal properties of FRP composites and bonding interfaces.