Sulfate Corroding Test And Analysis For Subway Segment Concrete Under Water Pressure

At present, our country has built a large number of subway tunnels. Because segment concreteis a typical porous medium, sulfate in external environment can diffuse into the concrete andreacts with some of the minerals. It will lead to the mechanical performance of segmentdegradation. Subway tunnel is usually built in underground, the water pressure may acceleratethe invasion of the sulfate and facilitate segment degradation. In order to research sulfatecorroding the segment concrete under water pressure, this paper has carried out the followingwork:1. Implement the compressive strength test and sulfate ion concentration test for segmentconcrete cube specimens and cylinder specimens which are immersed in sulfate solutionwithout water pressure for30,60,90,120,150days. Results show that:(a) the compressivestrength of segment concrete increases firstly and then decreases with the increase ofimmersion time and reaches maximum after being immersed for60days;(b) with the increaseof depth, sulfate ion concentration of segment concrete decreases quickly and has a steep fallbetween1.5mm and4.5mm;(c) sulfate ion concentration of cylinder specimens is slightlyhigher than the corresponding cube specimens at the same depth.2. Implement the compressive strength test and sulfate ion concentration test for segmentconcrete cube specimens and cylinder specimens which are immersed in sulfate solution with5m,10m,15m water pressure for30,60,90,120,150days. Results show that:(a) comparedwith no water pressure conditions, the water pressure above don’t obviously influence on sulfate corroding segment concrete;(b) pressure device in this paper not only is a simplestructure, but also provides stable pressure.3. Improve the Tixier R diffusion model. Then, use the improved model to simulate diffusionprocess of sulfate ion in segment concrete. At last, a comparison between simulation resultsand test results is made. Results show that: the improved diffusion model can better represent sulfate ion’s diffusion behavior in segment concrete.4. A compressive strength calculation model for corroded segment concrete is put forward byassuming that the compressive strength of corroded segment concrete is an underminedfunction of sulfate ion concentration. Then, a comparison between calculation results and test results is made. Results show that: calculation results from the model agree well with the testresults.