| Recently, the civil engineering industry has shown increased interest in using carbon fiber reinforced polymer (CFRP) composites. In the United States, there is increasing use of CFRP composites externally bonded to reinforced concrete structures for seismic retrofit or structural damage rehabilitation. The overall durability of these retrofit applications is of great importance to the long-term performance of the overall system, but is not understood well. Thus, a better understanding of durability characteristics of CFRP composite systems is needed. The primary objectives of this research were to provide information in support of National Cooperative Highway Research Program (NCHRP) Project 12-73, "Design Guidelines for Durability of Bonded CFRP Repair/Strengthening of Concrete Beams". This supporting research included: (1) Developing laboratory standards for epoxy resin mixing and application procedures for externally bonding CFRP composite systems to concrete beams, (2) Developing a method of nondestructive infrared analysis for quality control of laboratory manufacturing of beam specimens with externally bonded CFRP composite systems, and (3) Conducting moisture absorption and stiffness degradation studies on CFRP coupon specimens exposed to accelerated environmental aging conditions.; In the moisture absorption and stiffness degradation studies, both fabric and plate CFRP were evaluated utilizing different epoxy resin systems. Specimens were exposed to: dry control (DC) conditions, and immersed in water at: 30°C (86°F), 50°C (122°F), and 60°C (140°F). Exposure times for the specimens ranged from 7 days to 50 days. The results of the two studies show that varying amounts of moisture absorption and stiffness degradation of the specimens (minor to significant) occurred over time. Comparisons of the performances of the different CFRP composite types were made. |
