Multi-factor Time-varying Model Of Marine Environment Action On Concrete

In the study of marine concrete durability,the surface chloride concentration of concrete(Cs)represents the marine environmental action,and is a key boundary condition for quantitative analysis and durability design.The Cs is affected by many factors such as environment,material and time.The current Cs models ignore the coupling effects between material factors and exposure times,resulting in time-varying behavior that is not reasonably reflected.In view of this,this paper studies the time-varying law of the chloride environment action of concrete structures in marine tidal zone,splash zone and atmospheric zone.Firstly,based on the standardized long-term natural exposure test database,through the analysis of time-varying mechanism and the comparison of existing time-varying models,choose the calculation expression that reasonably describes the time-varying behavior;Secondly,studying the influence mechanism of binder types based on the database,a model is proposed to reflects that binder types action on the influence rule of water-to-binder ratio and exposure time for Cs analysis coupling relationship between water-to-binder ratio,exposure time and binder types.;Thirdly,Multi-factor time-varying models of marine environmental action on concrete in marine tidal,splash,atmospheric zone are established by two-stage multivariate nonlinear regression analysis;Finally,the validity and applicability of the model are verified by comparison with the experimental data and the existing model.The main research contents of this paper are as follows:(1)A large number of published test data generated in domestic and foreign durability research is collected lay a data foundation for the analysis of key factors affecting the mechanism and establishing a multi-factor time-varying model for chloride environment action to the concrete.The errors of test setup and method from different research groups should be drawn attention.Some standardization requirements listed and taken to corrected data are proposed by combining domestic and foreign norms and research results related to the chloride environment action and the boundary conditions require in durability design are combined,so as to establish a standardized database of different environmental regions.(2)Based on the long-term field data after standardization,study the variation law of chloride concentration distribution during the whole time-varying process from rapid growth to slow convergence,and compare the existing time-varying models to establish a more reasonable reflection of the inverse proportional function.The time-varying law can be used as the model predictive value stabilization time by calculation and analysis.At the same time,the mechanism that influence of material factor on Cs is analyzed,and the coupling relationship between material factors and exposure time is studied.A model with the correction factor of binder type is proposed to reflect the relationship between material factors and exposure time reasonably.(3)By studying the mechanism of chloride ion transport in different exposed areas,discussing the independence of the influencing factors according to the regional environmental characteristics and the mechanism of chloride ion transport,comprehensively consider the correlation of various factors to establish the tidal zone,the splash zone and the atmospheric zone.The multi-factor time-varying model of concrete chloride environment action is based on the large-scale experimental data of the corresponding zone.The two-stage multivariate nonlinear regression analysis method is used to obtain the model parameters.Then the mechanism analysis is used to determine the correction coefficient of binder type to reflect the rationality of stability time and stability value.Finally,compared with the experimental data and the existing model to verify the validity and applicability of the model.