Mineral-Based Bonding of Carbon FRP to Strengthen Concrete Structures

Abstract

The advantages of fiber-reinforced polymer (FRP)-strengthening have been shown time and again during the last decade. Several thousand structures retrofitted with FRPs exist worldwide. There are various reasons why the retrofit is needed, but it is not uncommon for the demands on the structure to change with time, as buildings and civil structures usually have a very long life. The structures may have to eventually carry larger loads or fulfill new standards. In extreme cases, a structure may need repair due to an accident or to errors made during the design or construction phases, and must therefore be strengthened before it can be used. Different methods to retrofit with FRPs also exist, such as bonding of plates or sheets, with their use of epoxy as the bonding agent being the commonality. Epoxy provides very good bond to concrete and is durable and resistant to most environments in the building industry. However, epoxy may also create problems in the working environment, needs a minimum application temperature, and creates diffusion-closed surfaces. These drawbacks can be overcome if the epoxy can be replaced with a cementitious bonding agent. In this paper tests are presented where the epoxy has been replaced with a cement based bonding agent for retrofitting. Pilot tests show that very good composite action can be achieved and that only minor changes in the design procedure need to be taken.