The Research On The Subway Concrete Of High Impedance And Impervious

The concrete for subway project is in coexistence corrosion environment of tray currents and the chloride ion, because of the mutual promoter action of tray currents and the chloride ion to the concrete destruction,therefore under this condition the duralble problem of concrete is more serious than general conditions, the key skills of solving this problem is promoting its resistivity and its impermeability, Backing State Natural Sciences Foundation Project(50772084), this article have following achievement:1) According to the special corrosion environment which the concrete for subway project in, proposed the design principle and method of concrete for subway project with high resisitivity and impermeability, provides the theory basis for the subway project concrete preparation.2)Studied the influence law of the admixture to the concrete resistivity and the impermeability, selects out the admixtures that could enhance the concrete resistivity and impermeability obviously; The result indicated that, the fly ash,slag powder,shale pottery and polymer have the obvious function to the anti-electric conductivity and the anti-chloride ion penetrating quality.comparing with the normal concrete when shale pottery replaces 30% of the river sand volume, its anti-stray currents characteristic and the anti-chloride ion seepage characteristic is better.3)Study on the improve mechanism of the admixtures to the resistivity and te impermeability , providing theoretical support for the subway project concrete preparation. The experimental result indicated that, the fly ash,slag powder,shale pottery and polymer have strong adsorption to the chloride ion, and obvious influnce to the OH^-, Ca²⁺ and Na+ ions density in pore fluid, the fly ash and the slag powder can reduce OH^-, the Ca2+ ions density in pore fluid, but the Na+ ions density increse slightly; through the gelatin seal to affect emptily to OH^-, Ca²⁺ and Na+ ions density in pore fluid ,the shale pottery reduces the ion concentration ;4) Propose the principle of design and the preparation method of high impedance and high impervious concrete, and tests the product perfomance of anti-stray currents characteristic and the anti-chloride ion ,and makes the microscopic analysis. The results indicate: the 56d resistivity of concrete is all higher than 100 kΩ.cm; and the 28d electric flux is lower than 350C , Compared with the same strength concrete its 180d chloride ion permeability depth reduce more than73.5% in natural environment, and more than 41.6% with the stray currents effecting 168h under the load stray currents condition, the corrosion rate reduce 68.3%, strength loss reduce 48% and its Surplus strength is although satisfyed the request of C50 concrete.