Experimental Study On Chloride Penetration In Cement-based Materials Under Different Dry-wet Cycleing Environments And Similarities Analysis

There are more and more durability problems of structures with the widely application of RC structures, especially under the chloride dry-wet cycling environments. Rebar corrosion will be caused by the ingress of chloride ions into concrete, which will reduce the bearing capacity of RC structures, and lead to the failure of RC structures.In present study, the chloride penetration experiments under different environment conditions of tidal zone and strong tidal zone in natural marine environment, and the salt spray and tidal zone in artificial climate environment were conducted. The influences of water to cement ratios, erosion time and different admixtures on chloride penetration were studied. The time-dependent models of chloride diffusive performance in different cement-based materials under the different dry-wet cycling environments were established and verified. the attenuation laws of chloride diffusive coefficients are analyzed based on the decay rate of the diffusive coefficients. According to the similarity theories, the similarities about the chloride ingress parameters are analyzed under the different dry-wet cycling environments. The main works of this paper are summarized as follows:1. Through a series of field trial with concrete and mortar in the tidal zone under the natural marine environment, the influences of the water cement ratios and different erosion time on the chloride penetration were studied. The time-dependent models of chloride diffusion coefficients in concrete and mortar under the natural marine environment was established and verified, and attenuate laws of the chloride diffusive performance were analyzed on the basis of attenuate rate of the diffusion coefficients. The result shows that the admixtures can improve the anti-chloride erosion performance of cement-based materials under the environment, and with the extending of test time, the time-dependent models can much more accurately reflect the attenuate laws of the chloride diffusion coefficient under the natural marine tidal environment.2. Through the long time ingress test of chloride penetration in concrete under the strong tidal environment, the impact of water to cement ratios, different erosion time, the contents and kinds of fiber on chloride ingress process were analyzed. The time-dependent models of concrete diffusive coefficients was verified under the strong tidal environment, and attenuate laws of the chloride diffusive performance have been analyzed on the basis of attenuate rate of the diffusion coefficients. The result shows that the igneous rock fiber can obviously improve the anti-chloride ions erosion performance of concrete, the larger contents of igneous rock fiber, and the better improvement is. The proved time-dependent models can be used as the predictor formula for the free chloride ions concentration of concrete under strong tidal environment.3. The laboratory simulation experiments of the chloride ions penetration in concrete were conducted in the salt spray environment under the artificial simulated marine environment, and the laboratory simulation experiments in the tidal zone under the artificial simulated marine environment were carried on. The impact of water to cement ratios and different erosion time on chloride penetration were studied. The time-dependent models of chloride diffusive coefficients of concrete was established under the artificial simulated marine environment, and the attenuation laws of the chloride diffusive performance in concrete.was analyzed on the basis of the attenuate rate of diffusion coefficients.4. On the basis of the classical similarly theories, the results between the field trials and the laboratory simulation experiments were compared and analyzed. The similarities of the free chloride ion concentration including the depths of convection zone and the peak concentration and the diffusion coefficients and the attenuation empirical parameters in different tidal condition were studied. Compared the results in the field exposure experiment with the ones in artificial simulated climate experiment, the accelerated effects was analyzed, and a uniform time-dependent model of chloride ions diffusion coefficient in different tidal environments is deduced.