This book provides an explicit description of the interface fracture behavior of FRP bonded concrete that is subjected to temperature and moisture effects. Extensive characterization of each constituent material is performed. Measured properties, in conjunction with peel and shear fracture load data, are used to calculate joint toughness by means of a newly developed tri-layer fracture model. Computed toughness, along with outputs of a fracture mode-mix analysis and a 3D moisture diffusion simulation are synergistically analyzed. Results suggest that moisture can physically change the property of a bond, and that of the adjoining materials. Joint toughness can degrade as much as 60% due to moisture ingress alone. Debonding mode will also shift from material decohesion to interface separation, which is rarely detected in short-term tests. Interface fracture analysis reveals why an initiated crack prefers to propagate along a debonded interface as opposed to bifurcating into concrete even though it appears to be the weakest link. This book aims to provide valuable test data and useful insights to structural engineers to design tougher retrofitted systems.