Carbonation Of Concrete Undere Air Pressure

In recent years,with the development of high speed railway,the construction of high speed railway tunnel has made remarkable achievements.The paper analyzes the effect of air pressure on tunnel concrete based on the environment condition of high speed railway tunnel with high air pressure when the high speed train passing through the tunnel.In consideration of high construction cost,lower maintainability and higher maintenance expense of high speed railway,and to be sure of its normal performance,carbonation properties of concrete of high speed railway tunnel to be studied urgently.Therefore,the research in this paper will be of great value for reference in durability study of high speed railway tunnel structure.The paper analyzes the mechanism of pressure formation and the effect of train velocity,the train/tunnel ratio and the length of tunnel etc on the pressure of high speed railway tunnel when the train passing through the high speed railway tunnel.The paper studies the effect of constant air pressure on concrete carbonation based on the penetration theory and experimental method.The contents and achievements of this paper mainly include:(1)The paper analyzes and calculates the carbonation depth based on the penetration theory and diffusivity theory under the condition of different air presssure.(2)The research is done with the self-development of pressurized carbonation tank.Thus imitating the concrete carbonation under the constant air pressure.(3)Carbonation is researched using the self-development of pressurized carbonation tank,and the test results are compared with the calculated results,both of them have good consistency.The results show that air pressure has a great effect on concrete early carbonation;With different air pressure,the greater air pressure is,the larger concrete carbonation depth is;At the same time,concrete carbonation depth increases with the increase of water cement ratio.(4)The paper analyzes the effect of fly ash and slag powder on the concrete carbonation resistance based on the calculated results.On the one hand,the contents of calcium hydroxide existing in cement hydration products decrease by the incorporation of fly ash and slag powder into concrete.On the other hand,the concrete permeability resistance increases by adding fly ash and slag powder into concrete,thus improving the concrete carbonation resistance to some extent.