Externally bonded fiber-reinforced polymer (FRP) composites represent a simple and economical solution for many repair and strengthening applications in concrete structures. However, the potential occurrence of sudden and brittle debonding failure in such repairs becomes prominent when FRP-concrete bond undergoes environmental degradation induced by moisture. Ambient-cured low-viscosity Bisphenol A epoxy adhesives are most commonly utilized in the engineering practice to bond wet-layup FRP to the concrete substrate. This study aims to elucidate the effects of Bisphenol A-based epoxy modified with commercial surface-modified nanosilica (SMNS), core-shell rubber (CSR) nanoparticles and multi-walled carbon nanotubes (MWCNT) on the improvement of mechanical properties of the epoxy adhesives, and strength and durability of FRP-concrete adhesively bonded joints. Moisture ingress in epoxy, DSC, tensile test on epoxy and three-point bending beam bond tests were performed. To determine the effects of environmental degradation, all specimens were subjected to the following environments: control—23 °C at RH 50 ± 10% for 18 weeks; and accelerated conditioning protocol (ACP)—water immersion at 45 ± 1 °C for 18 weeks. Improvement in mechanical properties were observed in dogbone specimens modified with nanoparticles without any reduction in glass transition temperature (Tg). In control conditions, nanomodified epoxy groups exhibited enhanced mechanical properties compared to the neat epoxy. Following ACP, strength, elongation and modulus of elasticity of neat epoxy deteriorated significantly, while no significant deterioration was observed in the nanomodified group of adhesives. Among all the nanomodified adhesive groups CSR Type-1 showed most improvement in mechanical properties over neat epoxy group both in control condition and in ACP. CSR-modified adhesive joints experienced practically no degradation when subjected to ACP and showed the highest maximum bond strength retention of 100% among all the adhesive groups. The bond strength of neat epoxy adhesive joints degraded most dramatically (15%) following ACP.
|Commitee:||Gopu, Vijaya K.A., McManis, Kenneth, Zhang, Qian|
|School:||University of Louisiana at Lafayette|
|School Location:||United States -- Louisiana|
|Source:||MAI 58/05M(E), Masters Abstracts International|
|Subjects:||Engineering, Civil engineering, Materials science|
|Keywords:||Bonded joints, Concrete, Durability, Epoxy, FRP, Nanocomposites|
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