Performance Of Fly Ash High Strength Concrete And Its Influence On Prestress Loss Of Bridge

With the development of traffic industy and the progress of science and technology, prestressed fly ash high strength concrete beams have been used widely in highway bridges. In prestressed concrete structures, prestress loss has a direct influence on the deflection and the crack resistance of the structure. Therefore, the accurate calculation of prestress loss has become an important research topic in the field of prestressed concrete. It is well known that the loss of prestress is mainly caused by elastic shortening, shrinkage and creep of concrete and steel relaxation, etc. But the research on performance of fly ash high strength concrete is insufficiency. It is in great need of deep research for promoting bridge engineering either from theory or realistic application perspectives.First, the mix design calculation method of fly ash concrete is obtained through the study of both abroad and domestic design methods. Second, by comparing fly ash high strength concrete and normal high strength concrete, the influence of the dosage of fly ash on compressive strength is analyzed. Early strength constructive formula and long-term strength prediction formula of fly ash high strength concrete are obtained. Third, the development of the elastic modulus of fly ash concrete is analyzed by investigating the influence of fly ash on compressive strength and the early and long-term prediction formula of elastic modulus of fly ash high strength concrete are gained.On the basis of analyzing different shrinkage and creep prediction models, the accuracy of existing models is compared by using B3variation coefficient method with test data in the Bazant-Li-2008database. Then a shrinkage and creep prediction model which is suitable for fly ash high strength concrete is established based on the experimental data and MC2010model.Finally, by using the experimental data and proposed model, this paper analyzed the influence of elasticity modulus, shrinkage and creep of fly ash high strength concrete on the loss of prestress of a prestressed concrete bridge. In addition, the results calculated by proposed method are compared with prestress loss calculated by the existing standand.