ABSTRACT
FRP sheets are often externally bonded onto concrete surface to strengthen concrete bridges. Salt-corrosion resistance of concrete strengthened with three types of FRP sheets, i.e. unidirectional CFRP, unidirectional BFRP, bidirectional BFRP, was evaluated by measuring the compressive strength and chloride ion concentration (CIC) profile after NaCl solution immersion. Results show that as exposure time increases, the compressive strength of BFRP-strengthened concrete decreases, while that of CFRP-strengthened concrete changes little, but both are higher than that of un-strengthened concrete. Internal CICs of FRP-strengthened concrete decrease significantly, with the reduction of over 80%. Wrapping bidirectional BFRP sheet shows the strongest chloride penetration resistance, followed by unidirectional CFRP and finally unidirectional BFRP. Chloride diffusion coefficient of the concrete shows obvious time and depth dependence, which reduces with time, and increases and tends to stabilize along depth. A model of chloride diffusion coefficient considering time-depth dependence was established to predict CICs in the concrete.
