The project reviewed and evaluated current practices relevant to the repair and retrofit of concrete structures using bonded fiber-reinforced polymer (FRP) composites, conducted an experimental program to investigate long-term performance of such repair, and based on tests results and other considerations, developed recommended construction specifications and a construction process control manual for such repair and retrofit.
There are no generally accepted construction specifications or process control procedures for repair and retrofit of concrete structures using bonded fiber-reinforced polymer (FRP) composites. The long-term performance of these applications is very sensitive to the process by which the FRP material is stored, handled, mixed, applied (including preparation of the underlying concrete surface), and cured. A finished FRP composite is characterized by both its constituent materials and the process by which those materials are formed into a composite. It is insufficient to characterize the composite by constituent materials only, as is commonly done. Assurance of as-designed properties is even more dependent on adequate process control in composites than it is in concrete. Because of the difficulty in quantifying the relationship between the long-term performance of FRP applications and the construction process, there has been no rational basis for construction specifications that will assure performance as designed. Highway agencies generally depend on composite materials manufacturers to provide construction process control. FRPs were developed for manufactured products, where processing could be tightly controlled. Many manufacturers prefer to provide their own construction process control, because guidelines and specifications are currently lacking. Although this arrangement has resulted in the most satisfactory outcomes, it may not be practical to continue this practice as this technology moves into widespread use. Therefore, there is a need to provide highway agencies with some means, such as a process control manual, to check the constituent materials and the adequacy of the construction process.
The first phase of research (Project 10-59A) focused on reviewing and evaluating construction practices related to FRP constituent materials and FRP systems, and developing preliminary construction specifications and a process control manual for the repair and retrofit of concrete structures using bonded FRP composites. The final report on the first phase of this project has been published as NCHRP Report 514.
The second phase of research (Project 10-59B) involved an experimental program to investigate the effects of different forms of surface preparation and FRP defects, and the range of environmental conditions encountered during construction on the long-term performance of the concrete structures that were repaired or retrofitted with bonded FRP composites. Results of this investigation were then used (a) to recommend enhanced construction specifications and a process control manual for the repair and retrofit of concrete structures using bonded FRP composites, and (b) to identify threshold values for surface preparation, FRP defects, and environmental conditions during construction. NCHRP Report 609: Recommended Construction Specifications and Process Control Manual for Repair and Retrofit of Concrete Structures Using Bonded FRP Composites documents the work performed in this project. Copies of NCHRP Reports 514 and 609 have been distributed to Program sponsors (state departments of Transportation).