Study of the behavior of epoxy resins used in strengthening systems when exposed to the accelerated degradation protocol proposed by ACI 440.9R (2015)

Abstract

As an alternative to strengthen reinforced concrete elements, techniques based on the use of composite materials formed by combining continuous fibers and bi-component resins have been used. Among the strengthening techniques, the Externally Bonded Reinforcement (EBR), directly applied to the concrete substrate of the element to be strengthened with epoxy resins, is one of the most used. Although FRP is widely used, the long-term behavior of the strengthening systems is unknown. Thus, the present work uses the accelerated conditioning protocol proposed by ACI 440.9R (2015) to evaluate the behavior of standard epoxy resins used in strengthening systems with FRP. Thus, primer and saturation resin specimens were exposed to two different environments recommended by ACI 440.9R (2015), laboratory and accelerated degradation, and tested after 1000 hours. The results showed that the epoxy adhesives maintained in the laboratory do not present reductions in their modulus of elasticity and maximum tensile stress. However, the resins exposed to the accelerated degradation protocol demonstrated reductions of up to 63% in the modulus of elasticity and up to 69% in the ultimate tensile stress.