Preparation And Performance Of Tunnel Secondary Lining Water-tight Concrete

Because the complex hydrogeological and harsh climatic conditions in thewestern region, the tunnel secondary lining concrete is more likely to appear thedurability problems, such as cracking, leakage, freeze-thaw damage and erosion. Theimpermeability of concrete is an important aspect of durability, the paper puts forwardthe design idea of the tunnel secondary lining concrete, which meets the requirementsof concrete, from the impermeability with specific climate and hydrogeologicalconditions.We study the cementitious material physical and mechanical properties,shrinkage property. We find ground limestone as admixture add to the cement-basedmaterials can increase the fluidity and the early strength of mortar; fly ashs canincrease the fluidity,the late strength and limit shrinkage of mortar; the mixture ofground limestone and fly ash reduce the early strength of mortar, but increase thefluidity, late strength, limit shrinkage of mortar better.The various factors of affecting the strength and impermeability of concrete wereresearched, and we study four main factors affecting impermeability of concrete byorthogonal experiment. The result show that water-binder ratio> the ground limestonereplacement> the fly-ash replacement> sand ratio, it means that the water-binderratio seriously affect the impermeability, the fly-ash replacement and the groundlimestone relatively low impact the impermeability, sand ratio is not significant forthe impermeability. According to the characteristic of secondary tunnel liningconcrete, we propose to use of low water-binder ratio, to add a large of admixture anda little of water reducer to balance relationship of concrete strength, impermeabilityand fluidity. Consequently, two group concrete are proposed by experiment. That is,the water-binder ratio are0.3,0.38; total admixtures are50%,30%. To optimize the best amount of mixing water and the outstanding compound admixture FSL byexperiment. Ultimately we find two mix proportions meeting requirement ofsecondary tunnel lining concrete and have test experiment of impermeability level, theimpermeability level reached more than P12. To Provide a reference for concretedesign of tunnel secondary lining.Through research analysis, the water-binder ratio is the most important factorthat affect the impermeability of concrete, the impermeability of concrete increasewith the water-binder ratio decrease, low water-bimder ratio is recommended on thebasis of meeting the other performances of the projects. Appropriate amount of fly ashand ground limestone can decrease shrinkage of cement base materials and improveimpermeability of concrete and meet the requirements of construction performanceand mechanics in engineering when applied in the tunnel secondary lining concrete,while to some extent improving the tunnel secondary lining concrete impermeability.A certain economic benefits can be made by reducing engineering cost from replacingfly ash and ground limestone.