Experimental Research On Chloride Ion Transport In Partially-buried Concrete On Soda Residue Soil

The high concentration of chloride ions in the pore liquid of soda residue soil will erode the interior of the concrete through multiple transport mechanisms,resulting in the durability decrease of the reinforced concrete structure built on it.There is no relevant research results on the durability of concrete structures in soda residue soil environment,which is worth studying.Based on physical tests and numerical simulations,this paper explores the transmission law of chloride ions and the prediction method of service life in concrete which is partially-buried in soda residue soil,and provides a basis for improving the structural durability of concrete in soda residue soil.Main research works carried out are as follows:(1)This paper employs the self-developed simulation test device of soda residue soil environment,aiming at two environmental variables,including groundwater level and soda residue soil saturation,which have a significant impact on chloride ion transmission.It simulates the real foundation environment of soda residue soil and conducts the natural diffusion test of chloride ions in partially-buried concrete,in order to further explore the distribution law of chloride ion concentration on the surface adsorption area and the underground area of it,with a comprehensive account of the changes of groundwater level and soda residue soil soil saturation.(2)By analyzing the measured value of chloride ion concentration in concrete specimens in different erosive environment,this paper explores the overall distribution law of chloride ions in partially-buried concrete in soda residue soil.It studies the transport process of chloride ions in soda residue soil soil and concrete,and explores the transmission mechanism of chloride ions in soda residue soil soil and in surface adsorption area and underground area in partially-buried concrete.(3)Based on Fick’s Second Law and the measured data of chloride ion concentration,this paper obtains the chloride ion concentration on the surface C_s and the apparent chloride ion diffusion coefficient D_a under different erosion environment by fitting and regression,and quantitatively analyzes the variation law of C_s and D_awith the groundwater level and the soda residue soil saturation.On this basis,a time-varying model of chloride ion transmission of the surface adsorption area and the underground area in partially-buried concrete is established,which comprehensively takes the groundwater level and the soda residue soil saturation into consideration.The accuracy and rationality of the transmission model are confirmed by comparing the predicted value of the model with the measured value of the test.(4)The existing research shows that the durability of concrete is mainly determined by the meso structures such as coarse aggregate,cement mortar,and interfacial transition zone(ITZ).Through the in-depth analysis of the measured value of chloride ion concentration in mortar specimen,it establishes the time-varying model of chloride ion transmission of mortar specimen,and proposes the calculation method of the chloride ion diffusion coefficient of cement mortar.The above research results provide an important basis for the mesoscopic numerical simulation of chloride ion diffusion in concrete in soda residue soil.(5)Based on the random generation and random placement algorithm of three-dimensional spherical coarse aggregates,it establishes a three-dimensional mesoscopic numerical model.By setting reasonable initial conditions,boundary conditions and parameters of every transmission medium,the diffusion behavior of chloride ions in it is numerically simulated.The correctness of the mesoscopic numerical simulation method and the evaluation results proposed in this paper is verified by the comparison with the measured values.On the basis of the time-varying model of chloride ion transmission and the mesoscopic numerical model established in this paper,it is attainable to predict the chloride ions concentration distribution of long-term diffusion and the service life in reinforced concrete structures of soda residue soil in Tianjin Port.