Strain hardening cement-based composite(SHCC)owning to its advantages of high ductility and control-lable crack width has been widely used in the strengthening and repairing of concrete structures exposed to severe marine corrosion zones.Based on this,a convection-diffusion model of chloride transport in SHCC subjected to marine drying-wetting cycles was proposed,and a two-dimensional mesoscopic model considering the chaotic distribution of fibers was established by COMSOL simulation software.The spatial and temporal distribution of chloride content under different drying-wetting ratios(3.0∶1,11.0∶1 and 85.4∶1)and exposure durations(30 days,90 days and 180 days)was analyzed by conducting a simulated indoor test of chloride ingress into SHCC.The effectiveness of the mesoscopic numerical model to simulate chloride ingress behavior was contrastively veri-fied.The results show that the peak chloride concentration inside SHCC increases with the extension of exposure time,and similarly increases with the increase of drying-wetting ratio.However,with the increase of penetration depth,the chloride concentration rapidly decreases and tends to be stable eventually,which make the chloride content as a whole show a higher peak concentration and a smaller penetration depth.According to the analytical solution to Fick's second law and considering the effect of convection zone,both the surface chloride concentration(Cs)and apparent chloride diffusion coefficient(Dapp)of SHCC show obvious time-varying characteristics.At a given drying-wetting cycle ratio,the Cs and Dapp increase and decrease as the exposure time increases,respectively.When the drying-wetting cycle ratio is 85.4∶1,compared to 30 days,the Cs of SHCC for exposure to 90 days and 180 days increase by 51.72%and 83.45%,and the Dapp decreases by 27.71%and 48.50%,respectively.At the same exposure time,as the drying-wetting cycle ratio increases,both the Cs and Dapp first increase and then decrease.Finally,the comparison between the measured data and calculated results of the chloride content distribution in-dicates the feasibility of the proposed convection-diffusion model under the cyclic drying-wetting action to depict the chloride transport behavior in SHCC.
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