Study On Simulated Experimental For Chloride Ion Erosion Of Existing Concrete And Elements

Chloride ions erosion is a main influence factor on insufficient durability of concrete structures. Under chloride environment, chloride irons penetrated in concrete will make reinforcement corrosion to shorted structural life, and may endanger the working safety of structures in shorter time.The background engineering in this paper is the existing concrete structures under the natural chloride environment. The core specimen of concrete lock gates are taken, and the chlorine ions concentration in the different depth of concrete cores have been tested and analyzed; some corresponding indoor experiments have been simulated, and the influencing factors on the anti-chlorine erosion performance of the simulating concrete specimen are researched, and chloride ions diffusion performance in the existing concrete and simulated concrete are also analyzed contrastively. Influence factors of the natural corrosion environment are designed and simulated, and the indoor experiments for erosion simulation of concrete beams have been made, and the chlorine ions concentration in concrete at different erosion time has been measured, the diffusibility and characteristic of chloride ions in the concrete beams under load have been analyzed. The protective effect of mortar protective course for anti-chlorine erosion of concrete structures under chloride environment is studied preliminarily.Based on the datum of the chlorine ions concentration of specimen in the natural environment and indoor simulated experiment, the main studies conclusions in this paper are in the following:1. In the condition of dry-wet circulation, the chlorine ions erosion district in the existing concrete under two-way erosion is made up of convection district and diffusion district, and so is the two-way appearance. The law of chlorine ions erosion in the diffusion district of the existing concrete above fits with the Fick's second law, basically. Diffusion coefficients of chloride ions in the existing concrete are increase with the increase of the chloride ions erosion depth, but the increasing trend is flat gradually.2. Under the indoor test conditions, there are better linearity relationships between tested chloride diffusion coefficients using the bridge method and the water-cement ratios and porosity and compression strength of tested concrete. According to the measured datum of chloride ions concentration in the existing specimen and tested chloride diffusion coefficients, the analytical model for diffusion coefficient of chloride ions in the existing specimen can be built preliminarily to consider the influence of the exposed time and temperature and so on.3. Under the designed experimental conditions, the chloride ions concentration in concrete of RC beams in loading adds along with increase of the stretching stress, and reduces along with increase of the compressive stress at the same erosion depth, generally. The chloride ions diffusion coefficient in the stretched district of pure bending section is about 1.5 times more than it in the pure shearing district of RC beams after 80d erosion. The chloride ions diffusion coefficient in the compressive district of pure bending section is about 0.5 times less than it in the shearing point and 0.6 times less than it in the unloading specimen. The chloride ions diffusion coefficients in the compressive district of RC beams decreases with the increase of erosion time in the same curing age.4. The thickness of outer mortar protective course should be not less than 5mm in order to decrease the chloride ions concentration in concrete. In the same erosion time, the water-cement ratio of outer mortar protective course daubs less, the thickness gets more, and then the chloride ions concentration is lower.