Study On The Workability Of Adhesives For CFRP Reinforcement

The technology of carbon fiber reinforced plastic(CFRP) reinforcing concrete structure has many outstanding features. For example, CFRP itself has advantages of high strength, light weight, the shape being freely cut, easy design, also the CFRP reinforcing concrete structure being convenient construction. So the technology of CFRP reinforcement has been widely used in the field of repairing and strengthening concrete structure, though it has been introduced in China just over ten years. The research on improvement of workability had been suspendly igored, although the workability of adhesives for CFRP reinforcing concrete structure directly impact on the effectiveness of reinforcement. This paper studied the different rheological characters of various thixotropic agents in the epoxy system, which was affected by shelf life, coupling agent and curing agent. According to satisfy the comprehensive performance requirements of adhesives for CFRP reinforcing concrete structure, the optimized formulation had been presented.Results showed that, when three thixotropic agents of hydrophilic nanosize SiO₂,hydrophobe nanosize SiO₂ and organobentonite were respectively dispersed in the epoxy system, effect of every thixotropic agents on viscosity and thixotropic was improved obviously, and was affected by shelf life, coupling agent and curing agent. The viscosity and thixotropic index of the part A adhesive with hydrophilic nanosize SiO₂ declined obviously, and was evidence by silane coupling agent. In the polar epoxy system, hydrophilic nanosize SiO₂ and alumina being complex in the ratio of 4:1 can result much better effect of viscidity and thixotropy than equivalent hydrophilic nanosize SiO₂. Popyamide curing improved the viscidity and thixotropy of hydrophilic nanosize SiO₂ in epoxy resin.The viscosity and thixotropic index of the part A adhesive with hydrophobe nanosize SiO₂ or organbentonite were steady, and thixotropic index was unchanged yet the viscosity was decline by silane coupling agent. The viscosity and thixotropic index of the part A adhesive which contained hydrophobe nanosize SiO₂ and silane coupling agent or organbentonite and silane coupling agent were steady. When the part A adhesive containing hydrophobe nanosize SiO₂ or organbentonite blended popyamide curing, the viscosity and thixotropic index of the mixtures were much lower than the part A. The optimized formulation of adhesives for CFRP reinforcing concrete structure had good workability also the mechanical properties can meet relevant national standard requirements.