Temperature Dependence of Cleavage Bonding Properties between CFRP Sheets and Concrete

Lately, the FRP adhesion method has become a subject of special interest. The bond strength between the FRP sheets and concrete influences the structural properties of reinforcement by this method. The influence of temperature on bonding properties between the FRP sheet and concrete should be investigated, since the properties of plastics are sensitive to an increase or decrease in temperature. The present article describes a study of the influence of bonding and curing temperatures, and the testing temperature on the cleavage bonding properties between the CFRP sheet and concrete. In order to obtain the cleavage bonding properties, compact tension tests were conducted, varying the bonding and curing temperatures, the testing temperature and the type of resin. The bonding and curing temperatures were 20 and 5°C, the testing temperature was selected from five levels within the range of -15 to 60°C. Epoxy resin and MMA resin were compared in the experiments. The relations between the load and the crack mouth opening displacement were measured as well. The cleavage bond strength, the bond softening diagram, the fracture energy and the toughness index were derived from the data as the cleavage bonding properties. The conclusions obtained from this study are as follows: 1) The cleavage bonding properties between the CFRP sheet and concrete are influenced remarkably by the testing temperature, although they are slightly influenced by the bonding and curing temperatures, and the type of resin. 2) The maximum value of the cleavage bonding strength and the fracture energy is obtained at a testing temperature of 20°C. Those properties decrease as the testing temperature increases or decreases. 3) The bond softening behavior becomes more ductile as the testing temperature increases. On the contrary, it becomes more brittle as the temperature decreases.