Study On The Influence Of Early Age Concrete Damage On The Mechanical Properties Of The Late Stage

The single pole early-dismantling formwork supporting system of aluminum slloy used as a kind of green template support system has been gradually applied in engineering,of which the bottom templates of beam and floor slab are removed after about 36 hours,and the late dismantling support system and the early age concrete structure of multi layer are used to bear the construction load.However,whether the construction load can cause the damage of early age concrete structure or affect the performance of the concrete structure in the late period of concrete has become the problem of great concern of engineers,which is badly in being solved for the engineering applications of aluminum alloy formwork system.From the beginning of 1950 s,researchers began to research the stress mechanism of early age concrete during the construction period.But up to now,the relationship between the age of concrete and construction environment,as well as the properties of early age construction damage are still much attention,of which research is still relatively rare.Therefore,the thesis mainly focuses on the mechanical properties of concrete in different ages under natural curing,as well as early age concrete under loading,which affects mechanical properties of concrete at the later stage.The research contents mainly include the following aspects:Based on different design strength grade of concretes,each design strength grade of concrete in different ages is used as the research object,analyzing effects of age and curing temperature on the mechanical properties of concrete at different ages.In order to study the effects of different parameters on the elastic modulus,splitting strength and stress-strain relationship of early age,the mechanical prediction formula based on the two parameters of the age and the curing temperature and the nonlinear stress-strain constitutive model for concrete based on age and curing temperature are put forward.According to the characteristics of the construction load,the different design strength grade of early age concretes prism specimens were carried out for a long-term tension test.The effects of concrete strength,axial tension strength,holding time and curing temperature on the mechanical properties of concrete are studied,and the corresponding strength,elastic modulus and stress-strain relationship prediction formula are put forward.According to the characteristics of the construction load,the different design strength grade of early age concretes prism specimens were carried out for a long-term compression test.The effects of concrete strength,axial compressive strength,bearing age and curing temperature on the mechanical properties of concrete are put forward.According to the prediction model of the bearing damage in the early age of the specimen,the reinforced concrete beam and prism concrete specimens with different damage degree are simulated by the ABAQUS finite element software.The test curves of prism concrete specimen and beam are compared with the curves obtained by the finite element simulation of ABAQUS.The results show that the experimental curves are in good agreement with the simulated curves.