CHLORIDE DIFFUSION IN CORAL AGGREGATE CONCRETE EXPOSED TO DIFFERENT MARINE CORROSION ENVIRONMENTS

In this paper, the chloride diffusion behaviour of coral aggregate concrete (CAC) exposed to marine submerged, tidal, and salt spray zones was investigated, and the effect of the fly ash (FA) content on the chloride diffusion was explored. The chloride concentration was measured using the potentiometric method, and the Ca(OH) 2 content in the CAC was calculated using the thermogravimetric method. The results show that the chloride concentration in the submerged zone decreases with an increasing erosion depth; meanwhile, in the tidal and salt spray zones, the chloride concentration showed a two-stage distribution pattern. The depth of the convective zone gradually increases with an increasing erosion time, and the depth of the convective zone in the salt spray zone is larger than that in the tidal zone. The chloride diffusion coefficient exhibits a power-function attenuation relationship with erosion time when exposed to different corrosion zones. The attenuation coefficient of the chloride diffusion coefficient increases with an increasing FA content. Moreover, the attenuation coefficient is the highest in the salt spray zone with it being 10.8 % to 28.5 % higher than that of the tidal zone. In addition, the Ca(OH) 2 content in the tidal zone is not only the lowest, but also gradually decreases with an increasing erosion time.