Experimental study of chloride transport law in concrete considering the coupling effects of dry-wet ratio and freeze–thaw damage

Abstract

In marine environment, dry-wet ratio (D/W) in the dry-wet cycling zone of coastal structures and freeze–thaw (FT) damage can both affect the chloride transport characteristics in concrete. In this paper, FT cycling tests of concrete specimens were conducted by the FT cycles testing machine to establish the relationship between the number of FT cycles and FT damage. Then, the chloride natural diffusion tests of concrete specimens with different FT damage under the dry-wet cycling zone were carried out to investigate the chloride transport law considering the coupling effects of D/W and FT damage on the condition of the dry-wet cycling period = 24 h. Under the influence of dry-wet cycles, there is a convection zone in the transmission of chloride in concrete specimens. Based on the Fick's second law, the convection zone peak concentration, the convection zone depth and the apparent chloride diffusion coefficient considering the coupling effects of D/W and FT damage were determined by fitting the chloride concentration distributions at various exposure time. The results show that the effect laws of D/W on unfrozen and frozen concrete specimens are basically the same. The convection zone peak concentration, the convection zone depth and the apparent chloride diffusion coefficient increase with the increase of FT damage in concrete specimens. The influences of FT damage on the convection zone peak concentration, the convection zone depth and the apparent chloride diffusion coefficient were quantified by introducing the impact coefficients of FT damage. Finally, a prediction model of chloride transport in concrete considering the coupling effects of D/W and FT damage was proposed, and the accuracy and reasonability of the prediction model were validated by comparing the predictive results of the model and the measured values of the tests.