Study On Railway Tunnel Lining Concrete Durability Improvement Technology In Sulfate Corrosion Environment

With the rapid development of China’s economic construction and the steady advancement of the “One Belt,One Road” strategy,the scale of railway transportation infrastructure construction is unprecedented.Tunnel engineering has become an important part of railway engineering because of its significant advantages in optimizing linearity,saving land and protecting the environment.The groundwater in southwestern China is rich in various corrosive ions mainly composed of sulfate,which causes corrosion degradation of tunnel underground lining,which seriously affects railway safety and efficient operation.Therefore,it is urgent to carry out research on durability improvement technology of tunnel lining concrete in railway engineering under sulfate corrosion environment.In this paper,the effects of mineral admixture types,dosages and different incorporation methods on the sulfate resistance of cement-based materials were studied by orthogonal test method for the deterioration of lining concrete of railway tunnels under sulphate corrosion environment.The result is to develop a concrete anti-sulfate attack inhibitor suitable for use in a sulfate-corrosive environment;By studying the pore characteristic parameters of concrete with different air content,the influence of the characteristic parameters of hardened concrete pores on the crystallization damage of concrete salt was investigated;The preparation technology of tunnel lining anti-corrosion self-filling concrete under sulfate corrosion environment is proposed.The research results of this paper not only provide guidance for the construction of tunnel lining concrete in the sulphate corrosion environment in southwest China,but also provide a scientific basis for the formulation of tunnel lining concrete durability design specifications.The effect of fly ash and silica fume on the sulfate attack resistance of cement-based materials is greater than that of slag powder,and the anti-erosion coefficient increases with the increase of fly ash content.Excessive silica fume content affects other mineral admixtures to improve the resistance of cement-based materials to sulfate attack.Considering the effects of different cementitious systems on the workability,mechanical properties and sulfate resistance of cement-based materials,the inhibitors are made of fly ash,slag powder and silica fume mixed in a certain proportion and supplemented with functional admixtures.The recommended dosage is 30% of the total amount of cementitious material.The proper introduction of tiny bubbles inside the concrete can alleviate the pressure generated by the crystallization of sulfate.When the gas content of fresh concrete is less than 5.6%,the proportion of harmful holes in hardened concrete is less,and with the increase of gas content of concrete,the bubble spacing coefficient of hardened concrete gradually decreases,and the specific surface area of bubbles gradually increases.Therefore,the salt-resistant crystallization damage performance of concrete is optimal under the condition of dry and wet sulphate circulation.This paper recommends that the optimum range of gas content of fresh concrete in the case of sulfate corrosion is 4.5% to5.5%.The field application results of sulfate attack inhibitors show that the work performance and durability of concrete can be significantly improved under the premise of meeting the structural design requirements of solid structural strength.At the same time,the amount of cementitious material and cement label of concrete mix ratio are reduced by adding sulfate corrosion inhibitors.The temperature rise peak of hydration temperature in lining concrete is reduced from 78.7 C to 70.1 C,which reduces the possibility of temperature cracks.