Randomness of bidirectional chloride corrosion of sluice gate and time to corrosion initiation of reinforcement in a strong tidal environment

Abstract

Six concrete core samples in the sluice gate exposed to a strong tidal environment have been drilled. Firstly, the chloride concentration with 1 mm interval was measured and the bidirectional chloride diffusion coefficient was fitted by Fick's second law. Besides, based on the probabilistic method, the randomness of each parameter which influences the time to corrosion initiation of reinforcement (including depth of concrete cover, peak values of chloride concentration, convection depth, chloride diffusion coefficient and critical chloride concentration) has been determined. And then, the Monte Carlo simulation method was used to analyze the probability of the time to corrosion initiation. Finally, sensitivity analysis was adopted to identify the main influence factor of service life prediction. Results indicated that the chloride diffusivity at positive side of gate is stronger than that at back surface. The time to corrosion initiation of reinforcement follows a normal distribution and the predicted mean value is consistent well with the actual measured value, confirming that in the strong tidal environment, the critical chloride content of 0.16%–0.18% by weight of concrete can be substituted into the service life prediction model. Besides, the depth of concrete cover is identified as the uppermost parameter which influences the time to corrosion initiation, followed by critical chloride concentration, peak value of chloride concentration and convection depth.