This research seeks to characterize the degradation of fiber-reinforced polymer (FRP) composite materials bonded to concrete and improve test methods used to assess the long-term health and performance of FRP/concrete in structural applications. Specific research areas include (1) accelerated laboratory testing of FRP/concrete samples to simulate long-term, outdoor field conditions (2) outdoor weathering of samples in different locations across the US, (3) relating accelerated laboratory results with outdoor field data, (4) identifying the mechanisms and kinetics of FRP bond degradation during weathering using spectroscopic (e.g., near and mid-infrared, Raman, etc.), mechanical (e.g., three-point bending, pull-off tests, peel tests, etc.), and thermal measurements (e.g., thermogravimetric analysis, differential scanning calorimetry, and dynamic mechanical analysis, etc.), (5) developing mechanical test methods for samples (at small and structural-level scales) before and after weathering, (6) developing test methods to evaluate the effect of defects at the FRP/concrete bond line on bond durability, (7) developing test methods for practical evaluation of FRP bond quality in the field, (8) developing non-destructive techniques to identify and quantify debonded areas at the FRP/concrete bond line, and (9) developing mathematical models to quantify moisture transport between concrete and the FRP bond during weathering. These studies provide quantitative data needed to improve building design and understanding of the long-term performance of FRP materials used to repair, strengthen, and seismically retrofit infrastructure.