Experimental Study And Probability Analysis On The Chloride Ion Diffusion Of Prestressed Concrete

Prestressed concretestructurehas the characteristics ofgood performance,large span,has been widely usedincivil engineering,water conservancyand traffic engineering and other fields of our country.However, a large number of engineering practice shows that structure function has degradated due to many unforeseen reasons in the long-term use of the process, resulting in service life can not achieve the target life. The main reason is due to reinforcement corrosion, but the greatest impact on the steel corrosion is chloride ion erosion.This paperstudied the chloride ionerosionproblems at compressive stress state of concrete, conducted a test on chloride ions invasion of concrete under artificial climate environment.The test considers the water cement ratio and stress level of two factors, design three different water cement ratio and stress state. In this paper,the work and research contentsare as follows:(1) In artificial climate environment, chlorine salt spray test to stress-free and compressive stress state of concrete, record and analyze test data;(2) Based on Fick’s second law, considering theeffect ofprestressing force,temperature, concrete chloride ion binding capacity,time dependence of the chloride diffusion coefficient, the structure defectsand other factors,establish chloride ion diffusion model ofprestressedconcrete under the effect of multiple factors;(3) Through the analysis of experimental datafound: different water-cement ratio of concrete in artificial climate environment,low water-cement ratio of concrete is better than high water-cement ratio of concrete on the resistance to chloride ion invasion, in this area will increase a certain percentage. Concrete in the compressive stress will have relatively large impact on chloride ion diffusion, the same water cement ratio of concretein the stateunder different stresses, in which the diffusion rateof chloride ion will decreases with compressive stress increases;(4) Based on this test data, chloride diffusion model was validated, the results show that the diffusion modelhasgood applicability,and provides a theoretical basis for thestudy of prestressedconcrete structure durabilityunder chloride environment;(5)The influence factors of the initial corrosion model were analyzed.It is found that the probability density function of basic parameters is different.The sensitivity analyses of theinitial corrosion time model is carried out,the study found thatinitial corrosion model have different sensitivity for these parameters, the influence of concrete protective layer on initial corrosion model is the most, the second is the critical concentration, followed by the diffusion coefficient of sensitivity, the surface concentration and stress of the lowest.