Numerical and experimental investigation on the chloride ion resistance of reinforced concrete piles externally bonded with CFRP sheets under dry-wet cycles

Abstract

Carbon fiber reinforced polymer (CFRP) has been widely used as a protective or restorative material for reinforced concrete (RC) structures present in marine environment. The free chloride ion profile is an important index for evaluating the durability of RC structures. Herein, three types of specimens were employed, i.e., ordinary RC piles (UC piles), RC piles bonded with CFRP (CP piles), and RC piles bonded with CFRP after a 2-year chloride attack (AC piles). Experimental free chloride ion concentrations (Cf) within UC piles and CP piles were measured by conducting an indoor test with the implementation of a marine environment simulation system. Predicted Cf in the three types of piles were captured through numerical models based on Fick’s II law and validated by test data. The results show that Cf of CFRP-bonded segments were significantly lower than that of ordinary RC segments. No obvious convection zone of chloride profiles was observed in the CFRP-bonded region in the dry-wet cycling zone. A “chloride redistribution process” occurred in AC piles, which would reduce Cf around steel rebars. Chloride resistance and thus durability enhancement to RC structures of CFRP were confirmed eventually.