Quality control and monitoring of NSM CFRP systems: E-modulus evolution of epoxy adhesive and its relation to the pull-out force

BackgroundIn Fibre-Reinforced Polymer (FRP) applications, the mechanical behaviour of the strengthening system strongly depends on the epoxy adhesive, particularly at early ages.MethodsThe present paper describes the application of an innovative technique (termed EMM-ARM: Elasticity Modulus Monitoring through Ambient Response Method) for continuous monitoring of the stiffening process of an epoxy adhesive used in structural reinforcements applications. A simultaneous study of direct pull-out tests with concrete specimens strengthened with near-surface mounted (NSM) carbon FRP laminate strips was carried out to compare the evolution of bond performance with the E-modulus of epoxy since early ages.ResultsThe peak pull-out force and the epoxy E-modulus obtained by EMM-ARM exhibit very similar evolution kinetics.ConclusionsA relationship between the evolution of epoxy E-modulus and the maximum pull-out force is assessed, highlighting the potential of applying EMM-ARM for quality control and decision-making assistance of NSM systems.